SOME ARTICLES FROM ENGINEERING NEWS RECORD.
TRADE CENTER BUILDS UPWARD FAST
The World Trade Center project in lower Manhattan last week entered a new phase of construction. A crane placed the first of 76 huge steel columns, shaped like short-handled pitch-forks, that will transfer the load of 101 stories of office space to the substructure. The four-story columns are the largest structural components of the project's twin 110-story towers.
Fig 1. World Trade Center's first 110-story tower is already up to 10th floor level above grade; excavation is almost complete.
The building's architectural design dictated the shape of the columns, says Francis H. Werneke, assistant construction manager for the project. He says the base of the building has exterior columns on 10-ft c-c, up to the fifth floor above plaza grade. Above the ninth floor, the columns are 3 ft 4 inches on centers. The tree columns make the structural and design transition.
The exterior wall elements are all loadbearing and take the full wind load for the entire structure.
Fig 2. Tree columns are 51 ft long, weigh up to 51 tons.
Kangaroo cranes lift the columns into place. Starting this week, they will each attempt to place two columns a day, erecting on all four faces of the tower simultaneously. Permanent floor beams tie the columns to the core.
Above the ninth floor, the exterior wall will be made of prefabricated units of three 3-story columns.
The project owner, the New York Port Authority, says that excavation is now 95% complete. Work has started on the grillage and footings for the second tower, concrete and steelwork is under way for the low-grade areas of both towers, and concreting on the floor of the first tower and plaza.
March 13, 1969
Fig 3. Crane lifts column atop fifth floor exterior columns.
WORLD'S TALLEST TOWERS BEGIN TO SHOW THEMSELVES ON NEW YORK CITY SKYLINE.
After nine years of planning and four years of demolition, excavation and construction, the world's tallest buildings, the 1,350-ft, 110-story twin towers of New York City's World Trade Center, are at last beginning to show on the city's skyline.
Steel on the North Tower has reached the 43rd floor and that on the South Tower is up nine floors.
Both towers are moving up fast. The construction schedules call for the erection of three floors of steel on each tower every 10 days. This is a rough schedule, but Karl Koch Erecting Co., Inc., of New York, which holds the $20-million erection contract, met this schedule several times before an elevator strike in July stopped work on upper stories. Once, the company did it in nine days.
Currently, Koch is working in an area of atypical construction on the North Tower, so the schedule can't apply. On the 41st and 42nd floors, both towers will house mechanical equipment. To accommodate the heavy loads, the floors are designed as structural steel frame slabs. All other floors from the ninth to the top (except for 75 and 76, which will also carry mechanical equipment) have typical truss floor joists and steel decking.
Fig 4. Ironworkers set a three-story high wall panel (notice the top chord knuckles above the decking).
Typical office floors have 4-in. thick slabs of composite construction using top chord knuckles of the joists, which extend into the slab, as shear connectors. On mechanical floors, composite action is provided by welded stud shear connectors.
Since Koch is assembling the truss floor sections under a separate $2.5-million contract, and they arrive at the site as ready-to-place sections 20 ft wide and up to 65 ft long, installation of typical floors is faster than the floors with structural steel frames. When Koch gets to the typical floors, it expects to achieve the 10 or even nine-day cycle.
The $600-million project is being built by the Port of New York Authority (PNYA) on a 16-acre site in downtown Manhattan near the Hudson River. Work is under the direction of Malcolm P. Levy, chief of planning and construction, and R.M. Monti, construction manager. According to Francis H. Werneke, assistant construction manager, the project will be completed, in stages, by 1973. Initial occupancy of lower floors in the North Tower is planned for the end of this year, although upper floors will still be under construction.
In addition to the two towers (which top the Empire State Building by 100 ft), the center will include a U.S. Customs House, two low-rise exhibition and trade development buildings and a high-rise hotel.
The work involves more than 700 contracts, which Tishman Realty & Construction Co., Inc., of New York City, agents for PNYA, coordinate and administer.
Plenty of office space. When completed, the center will have more than 9 million sq ft of office space. It will provide office and shop space for more than 50,000 persons and will be visited daily by another 80,000.
Each tower is 209 x 209 ft in plan and is column-free between the exterior walls and the 79 x 139-ft core, thus providing 35-ft clear spans on the east and west sides and 65-ft clear spans on north and south sides. In addition to the usual service and utility rooms, the core of each tower will contain 104 elevator cabs running in 36 shafts. This unusual arrangement is made possible by the use of 23 shuttle express elevators which will discharge passengers into so-called skylobbies where they transfer to local elevators. As a result, as many as three elevator cabs will use a single shaft.
Before construction could begin, a 70-ft high, 3-ft thick concrete wall was built below ground around an eight-block area by the slurry-trench method. Then, 1.25 million cu yd of rock and earth within were excavated.
In the hole, contractors are building what is undoubtedly the world's largest basement. It is 980 ft long, 510 ft wide and close to 70 ft deep. Its six levels provide a total of 48 acres of floor space and will house, among other things, a 2,000-car garage.
And through the basement now are two ancient subway tubes through which run commuter trains between New Jersey and New York.
New tubes and station. Before the center is finished, and after a new station is built in its basement, the presently exposed sections of the old tubes will be removed.
Into the towers rising from the excavation are going some 200,000 pieces of steel having a total weight of about 200,000 tons (about 1/5 of the total weight of the structures). Individual columns in the lower core section, measuring 52 x 22 in. in plan, are formed of 5 and 3-in, plate into almost solid steel shafts that weigh up to 56 tons.
Fig 2. Columns in lower core are almost solid steel and weigh up to 56 tons each.
The site creates logistics problems. City streets adjacent to the site are narrow and congested. There is little or no room at the site to store materials. Therefore, every piece of structural steel must arrive at the right place at exactly the right time. Currently, there are 12 receiving points on the job for the 600 tons of steel that are trucked to the site daily. Eight of these are under the booms of the four climbing cranes atop each tower. Four others are under the booms of mobile land rigs that roam the site as needed.
A mistake in the time, sequence or place of arrival of a single vital part could stop erection of either tower. Preventing this is not easy.
Raw steel is shipped to some 15 fabricators around the country and from several foreign countries. (Unofficial estimates of foreign steel being used in the trade center range from 30 to 60% of the total.) The fabricators ship completed units to the Greenville railroad yard in New Jersey, just across the Hudson River, where they are stored before being trucked to the site. As of now, with 71,000 tons of steel in place and another 60,000 tons in Greenville, every piece has reached Greenville on time and in proper sequence.
Computer-controlled. This record is attributable largely to a computer-programmed control system set up by PNYA engineers in a six-month period of concentrated planning, testing and debugging.
Under the program, each fabricator gets, with its basic contract plans, a schedule that tells when individual segments of material are to be produced. The fabricator then prepares shop drawings and shipping lists for PNYA. PNYA feeds information on each individual piece into its program, showing scheduled completion at the plant, expected time for rail delivery to Greenville, a month's contingency layover in Greenville and the actual erection date.
Follow-up data from representatives of independent inspection laboratories stationed in each fabrication plant and from PNYA men at Greenville and the job site are fed into the program daily to keep it current. So detailed is the program that PNYA engineers can get schedules on a hourly basis if necessary.
Fig 3. Three-column wall panel is hoisted.
Because of the tremendous volume of information in the program, printouts work only by exception, i.e. they report on only the material that is behind schedule at any point in the production chain. (An ideal printout would be a blank sheet of paper, but William Borland, who is responsible for coordinating material deliveries, admits that he hasn't seen one yet.)
The largest contract for fabrication of structural steel is held by Pacific Car and Foundry Co., of Seattle. It is $21.79 million for 55,000 tons of steel for the towers' bearing wall panels from the ninth floor up.
In all there are 5,828 of these panels, each about 10 ft wide, 36 ft high, with the heaviest individual panel weighing about 22 tons. Each panel consists of three box columns, 14 in. square, made up of plate up to 3 in. thick and, connected by 54-in, deep spandrels.
When the panels are delivered to the site, Koch lifts them off the trucks and raises them to their proper locations with one of eight Australian climbing cranes the company purchased especially for the job. (PNYA recently bought the cranes from Koch to simplify their use by other trades when they are not needed for steel erection.)
Succeeding panels are bolted together by means of high-strength bolts installed through handholes in the box columns, which are accessible from inside the building. Gusset plates and high-strength bolts connect adjacent spandrels, and these connections are also made from within the building.
January 1, 1970.
Fig 1. North Tower is up 43 floors. South Tower follows.
FOUNDATION FOR TALLEST TOWERS: WATER OUT, TRAINS IN
The world's tallest buildings, the World Trade Center's twin towers, will stand on one of the biggest, most complex foundations ever built.
For example, to install the foundations, a joint venture of five contractors working for the Port of New York Authority is still digging 70 ft into Manhattan's west shore to remove 1.2 million cu yd of rock and earth from a box-shaped excavation. The box is lined with 3,000 ft of cutoff wall that has a 64-ft head of water outside-and no internal bracing.
Fig 1. Steel rises for north tower while south tower area is dug.
All of the digging must be. done over, under and around a pair of subway tunnels that carry nearly 600 commuter trains through the excavation daily. Without interruption of train traffic, the live and dead loads of about 1,000 ft of each tube must be transferred from the soil to a suspension system that will hold the tubes about 30 ft in the air for the next 2 years.
The cutoff wall, which Icanda, Ltd., an affiliate of Icos of Milan, Italy, installed by the slurry methods, is roughly 3 ft thick and completely encircles a 1,000 x 500-ft area (ENR 4/13/67 p. 62). Though its base is keyed about 3 ft into rock, the wall itself will not withstand the hydrostatic pressures from without. Therefore, the PNYA engineers designed a system of exterior anchors that will support the wall until the complex's heavily reinforced subfloors take over the job.
Fig 2. Track Drill sockets rock through casing it drove previously.
The key to the anchoring system is five tiers of tendons sloping down through the wall and the earth outside it into about 35 ft of rock, where they are grouted (see drawing). The tendons, comprising eight to 24 high-tensile steel strands, are subsequently stressed, then locked to the wall. The wires are grouped around a ¾ -inch I.D. plastic tube, which carried the grout to rock sockets before being extracted from the hole for reuse. The contracting group began excavations in interior areas even before the walls were completed. As wall sections were finished, the contractors followed with excavation adjacent to them.
Fig 3. Anchorages eliminate inside braces.
To maintain an internal pressure on the walls, the contractors did not excavate the area near the walls to the 15-ft depth required for installation of the first tier of tendons. Instead they left the area high and dug trenches down towards the wall for access. The contractors followed this procedure on each subsequent tier. Then, using a modified drill rig, they drove 6-in diameter. pipe casing through the anchor inserts cast in the wall. When the casing met refusal, it was cleaned with air, then re-driven. When the casing was seated on rock firmly enough to be watertight, the contractors then used a tungsten carbide bit to drill the socket.
Fig 4. Trusses and saddles hold subway tube.
Dig, then measure. Because the length of each tendon varied with the depth of the rock, there was no way to determine tendon length until each hole was drilled. Therefore, after the depth of each hole was determined, the contractor telephoned the tendon fabricator, Carroll-McCreary-National Prestress, of Corona, N.Y., to give the hole number and length.
Since the sockets could not be left open too long, fast delivery of tendons was a must. Carroll worked around the clock to deliver individual tendons within 4 to 6 hours after receiving information. The firm delivered more than 1,400 tendons, ranging from 100 to 150 ft long, at the rate of six to eight per shift, with a maximum of 22 in a single day. This fast delivery, according to James Hastie, assistant project manager, for the joint venture, was an important factor in keeping the job on schedule.
Tendon placement was simple. Workmen set the reel on an A-frame stand and fed the tendon into the proper hole. To keep the strands from getting away, the stand was equipped with a hand brake.
The contractor then grouted the socket from the bottom to a distance about 2 ft above rock with a mixture of high-early strength cement, water and fly ash. The required 3,000 psi concrete was usually obtained in 72 hours. The contractor could then stress the tendons.
To test each tendon, the contractors stressed it to 80% of its ultimate strength, then relaxed it to a tie-off load of about 65%. For the most part, the tendons are designed to withstand loads of from 200,000 to 600,000 lb. During the tests many were successfully stressed to as much as 800,000 lb.
With the tendons stressed end locked, the contractor filled the empty casing with a bentonite slurry to prevent the intrusion of salt water or other corrosive materials. The tendons contain a heavy zinc anode for cathodic protection.
Routine dewatering, but. Because the cut-off walls are virtually impervious, the contractors' water problems are limited pretty much to handling the water trapped within them. Therefore, except in the areas of the subway tubes, where water elevation was extremely critical, the dewatering is routine.
Initially the contractor installed four deepwell sumps 8 ft sq. The sumps did dewater adjacent areas, but no more, because of the impermeability of the ground. This was not serious, however, since 2-in, and 4-in, centrifugal pumps in local areas controlled the water.
PNYA specifications called for lowering the water table outside the excavation to a depth of 5 to 10 ft. Rather than install well points all around the perimeter, the contractor had Icanda cast a 4-in, hole in each 22-ft wall section. With these open, the water from outside ran into the excavation, where the pumps sent it through a header system to the Hudson River nearby.
Handling water near the two subway tubes was another matter. The tubes, 16 ft 7 inches in diameter, carry the Port Authority Trans-Hudson (PATH) tracks under the Hudson River between New York and New Jersey. Around the tubes, the contractors had to maintain a delicate balance between water and earth. Without the proper balance, the tubes might have floated or sunk.
Balance maintained. To maintain balance, a three-stage ejector wellpoint system was installed on both sides of each tube. One stage went to the spring line, one went a little below it and one to rock.
By the extensive use of piezometers and some extremely accurate calculations, the contractor was able to maintain a vertical balance. To prevent any horizontal movement, PNYA specified that there never be more than a 3-ft variation in ground elevation on either side of a tube.
To support the tubes as the earth was removed from under them, the contractor installed a line of 24-inch diameter caissons 40 to 50 ft c-c on either side of each tube. These were socketed into rock 2 ft below final subgrade, cleaned, and filled with a steel core and concrete before any excavation was done.
During this operation, the PNYA had manned listening posts inside the tubes with telephone connections to the rigs above.
Telephone Communications were also maintained whenever work was performed within 10 ft of the tubes.
The contractor was allowed to excavate to 2 ft below the spring line, cutting off the caissons as he excavated to keep them out of his way. At this point the contractor cut the caissons and capped them with steel plates. American Bridge Division of U.S. Steel Co. spanned the caissons with trusses 8 ft deep and spanned the tube with WF beams.
The contractor then cut a 5-ft-wide transverse trench under the tube and slid a saddle through it. The saddle was attached to high-strength rods extending from the cross-members above, and the rods were tensioned to pick up the load of the tube.
One at a time. To prevent settlement, the contractor was allowed to dig only one trench at a time in each bent, since 10 ft was determined as the maximum length of tube that could be left unsupported. To speed the work, however, the contractors used wide, fiat steel straps that would be slid under the tubes at the edge of each hole to temporarily support the tube while another trench was cut for another cradle.
With the tubes safely supported, the contractor covered each with 3 x 12 fire retardant plank decking supported on 12 x 12 timbers. This will provide the tubes with protection against falling objects. The tubes then will be removed and replaced by new tracks in a new PATH terminal under the new buildings.
The general contractor on the $18.7 million foundation is West Street Associates, a combine of Slattery Associates, Inc.; Gull Contracting Co., Inc.; Poirier and McLane Corp; Tully & DiNapoli, Inc., and Spencer, White & Prentis, Inc., all of New York City.
The trade center foundations were designed by the Port Authority engineering department.
October 31, 1968
Fig 5. Excavation goes on all around subway tube while trains run without interruption.
Fig 6. Tension strands are threaded through safety plate before stressing cables.
TALL TOWERS WILL SIT ON DEEP FOUNDATIONS
By Martin S. Kapp
Soil problems in the lower Manhattan site of the world's tallest buildings, the twin 110-story skyscrapers planned for the Port of New York Authority's $350-million World Trade Center, require construction techniques no less unusual, if less spectacular, than the erection of prefabricated steel framing planned for the superstructure (ENR Jan. 23, p. 33).
The chance of settlement of surrounding structures caused by conventional dewatering for construction in the dry favors the slurry-trench method of building the deep foundation walls. In this method, a bentonite slurry pumped into an excavated trench retains the earth, while tremied concrete forms the walls.
Fig 1. Slurry-trench method: (1) special excavation rig churns up material from trench; (2) tremie pipes place wall concrete; (3) displaced slurry is pumped into another trench.
Prestressed rock anchors will resist lateral loads to retain the deep basement walls built by the slurry-trench method. This will speed excavation by eliminating the obstacle course of rakers normally cluttering up an excavation and speed construction inside the basement walls.
The World Trade Center will occupy a 16-acre site in the lower West Side of Manhattan, near the Hudson River (ENR Jan. 23, p. 33). Under an open five-acre plaza surrounding the towers will be five basement levels for mechanical equipment and parking for 1,600 automobiles. The basement area will extend beyond the boundaries of the plaza, covering a 7.5-acre area. The total project will require the removal of 1 million cu yd of earth to depths up to 75 ft, and the rock-based foundations will carry 1.25 million tons of superstructure load.
A continuous footing will support the closely spaced exterior columns of each skyscraper. Continuous footings will also support the interior columns, the largest of which are 54 x 26 inch, plate box sections. All columns will have two-tiered grillages of heavy steel sections (see drawing).
Contractor's nightmare. The lower Manhattan site of the World Trade Center is suited more to an archaeological expedition than foundation construction.
During the past 180 years, fill has extended the shore line about 600 ft westward into the Hudson River. Excavators may hit boulders, timbers of old wharves, or even a buried ship. Soil profiles indicate layers of fill, organic silt, and sand and gravel above the rock stratum of Manhattan schist about 65 ft below grade.
The gravest problem confronting a foundation contractor using conventional procedures would be the hazard to streets and structures caused by lowering of the surrounding groundwater level. Dewatering the area to the required depth with well-points or deep wells might settle West St. as much as 18 inches. West St. runs parallel and adjacent to the shoreline. Since the overburden above compressible soils would no longer be buoyant after lowering of the groundwater level, and therefore increase soil pressure in those lower strata, buildings on spread footings above the rock level could settle.
Still another problem springs from the possibility of temporary delays in acquiring property, closing streets and relocating utilities. These delays may require construction of the basement in unconnected segments rather than a continuous line.
And still another disadvantage of conventional construction would be the need for a heavy pressure slab (about 15 ft thick) to resist the hydrostatic pressure. A thinner slab designed to resist this pressure would require permanent anchors. Use of these anchors would be questionable because of possible corrosion.
Normal methods of deep basement construction can't solve these problems. Boulders and other obstructions could buckle the steel sheet-piles or soldier beams as they were driven. Other modifications, including water recharging (restoring the water table outside an excavated dewatered excavation by recirculating water through a supplementary wellpoint system), freezing and chemical grouting, do not appear practical or economical.
Concreting in a slurry. In the slurry-trench method, a shallow trench is excavated in segments around the perimeter of the basement. A special drilling, chopping and excavating rig set up over the trench churns up and sucks out material from a 3-ft-wide trench section, 20 ft long (see sketch). (Excavating the trench in segments adapts it for the delays in property acquisition or utility relocations.)
Fig 2. Foundation wall sequence: (1) dig slurry trench, cast cut-off wall; (2) excavate, install rock anchors; (3) excavate, install rock anchors, build footings and slab.
Pumped in and, recirculated while the excavation work proceeds, bentonite slurry retains the sides of the trench (ENR April 26, 1962 p. 100). It has a higher specific gravity than the soil it replaces.
After the contractor has excavated the trench into rock, a prefabricated reinforcing cage is lowered into the slurry. Concrete is then tremied in, displacing the slurry, which then may be piped into an adjacent segment as excavation proceeds. Alternate panels are completed this way, and when the concrete has set, the space between wall panels is completed in the same way. The end result is a reinforced concrete cut-off wall, 36 inch thick, socketed into the rock and serving as the outer, structural part of the basement wall.
Though it has been previously been used for subway and building foundation construction in Europe and Canada, the Port Authority believes that the World Trade Center will mark the first U. S. slurry-trench operation for buildings.
The contractor will remove existing buildings and excavate to water level simultaneously with the wall construction. The completed wall will seal the basement from the outside. Excavation continues inside. Pumping is required only to expel the entrapped water, thus leaving the water table outside the basement area unaffected.
Prestressed rock anchors. To keep the progressing excavation free of conventional bracing obstructions, the Port Authority has planned a system of prestressed rock anchors (ENR June 8, 1961, p. 34). They free an excavation
The prestressed rock anchors fit into a series of inclined, cased holes. Then a socket is drilled into the rock. The tendons are inserted into the holes and grouted into the rock sockets. These rock anchors are pretested with jacks to loads above their required design capacity and then anchored to the wall, forming external tension, braces. As excavation continues, additional rows of tie-backs are placed for new horizontal bracing lines.
Fig 3. Tower foundation comprises continuous footings. Grillages for column foundations will sit on leveling pads cast on rock.
When the excavation has reached subgrade elevation, the footings for the tower foundations and the plaza structure foundations are carried into the rock. Piers for these foundations will then be concreted, a gravel drainage blanket placed over the entire site, and a 12-inch thick floor slab cast. Then the site is ready for erection of columns and floor framing, which will brace the walls and make the rock anchors no longer necessary.
A permanent pumping system will be used to take care of the small amount of seepage filtering through the wall and the rock.
Still another advantage of the proposed system is its relative quiet compared with the driving of sheet-piling.
The Engineering Department of the Port Of New York Authority is designing the World Trade Center foundations. John M. Kyle is chief engineer; Ame Lier is structural engineer; and Martin S. Kapp is soils engineer. Malcom P. Levy is chief of the Port Authority's World Trade Center Planning Division.
Prefabricated steel framing. The steel superstructure rising from the continuous foundations will contain steels of four basic stress grades A36 (36,000psi yield strength), A441 (50,000-psi yield strength), high-strength steel (65,000-psi yield strength) and heat-treated constructional alloy steel (100,000-psi yield strength).
The exterior walls will comprise giant Vierendeel trusses, designed to act like huge cantilevered hollow tubes. They will be pre-assembled in units two stories high and about 10 ft wide, spliced at mid-height of the columns and midspan of the deep spandrel beams. The closely spaced columns will consist of 14-inch-sq hollow box sections, providing high torsional and bending resistance.
Architects are Minoru Yamasaki & Associates of Birmingham, Mich., and Emery Roth & Sons, of New York City. Structural engineers are Worthington, Skilling, Helle & Jackson, of Seattle.
Mr. Kapp is Engineer of Soils in the Port of New York Authority's Engineering Department, which designed the foundations for the World Trade Center.
Fig . Center will rise from 70-ft-deep basement covering 7 1/2 acres.
July 9, 1964
Four New York City construction companies will independently review construction techniques planned for the two 110-story towers at the World Trade Center (ENR Jan. 23, p.33 and April 2, p. 43). The firms, Diesel Construction Co., George A. Fuller Co., Tishman Realty & Construction Co. and Turner Construction Co., will each receive a $15,000 fee. Their reports on materials, techniques, time and cost are due in June.
April 16, 1964
The Port of New York Authority will. pay architects Minoru Yamasaki & Associates and Emery Roth & Sons an extra $800,000 over the initial $1.5-million fee for designing the World Trade Center in New York City. The new contract covers further design refinements for the superstructure of the twin 110-story towers, studies of integration of the PATH railroad station into the project.
October 15, 1964
FIRST STEP TO A RECORD
With the $700,000 purchase of an 18,800 sq-ft parcel in lower Manhattan, the Port of New York Authority took the first step in the long journey toward its $350 million World Trade Center. Excavation should start this year; completion is to be in 1970. The project will boast the world's tallest buildings: twin 110-story skyscrapers designed by Minoru Yamasaki.
April 1, 1965
BIDS ON TALLEST BUILDINGS
Bid call for the first contract for the Port of New York Authority's $350-million World Trade Center, originally forecast for late 1965, is now expected in the spring of 1966. The project will boast the world's tallest buildings twin 110-story skyscrapers that will dominate lower Manhattan's skyline.
July 8, 1965
HOW COLUMNS WILL BE DESIGNED FOR 110-STORY BUILDINGS
For record-height towers of New York's World Trade Center, engineers proportion columns to avoid floor warpage when high-strength steels are used for exterior columns and A36 steel for interior columns.
A design procedure that will be used for structural framing of the 1,350-ft high twin towers of the World Trade Center in New York City gives the exterior columns tremendous reserve strength. Live loads on these columns can be increased more than 2,000% before failure occurs.
The procedure calls for proportioning of columns in each story for the same unit stress under gravity loads, regardless of the grade of steel in the columns. Thus, all columns will shorten the same amount, and differential shortening will be eliminated as a possible cause of floor warpage. The reserve strength of high strength steel members will then be available to resist wind stresses.
The structural engineers adopted this particular design because of the great length of the columns, use of different grades of steel and their plan to take wind stresses in the exterior columns only.
The concept was explained to the New York Architectural League by John Skilling, a partner in Worthington, Skilling, Helle and Jackson, of Seattle, consulting structural engineers on the World Trade Center (see p. 124).
Record-height towers. The. Port of New York Authority's World Trade Center will provide offices and exhibit areas for government agencies, trade services and private business concerned with exports and imports. The project will occupy a 16-acre site along the Hudson River in downtown Manhattan. Its twin towers, 110 stories high, will be 100 ft taller than the Empire State Building (excluding its TV antennas on top), currently the world's tallest building (ENR Jan. 23, p. 33). Rising the full 1,350-ft height without a setback, each tower will be 208 ft square. It will be designed to resist a 45-psf wind, with both low sway and low acceleration.
Exterior columns will be spaced 39 inches c-c. Made of various high-strength steels, they will be 14-inch square hollow-box sections, for high torsional and bending resistance, and windows will be set between them. Spandrels welded to the columns at each floor will convert the exterior walls into giant Vierendeel trusses.
Interior columns are all in or around the elevator-stairway core. Thus, the office areas are free of columns. All the core columns will be made of A36 steel (36,000-psi yield point). As a result, corner columns at the base of the core may be solid steel as large as 2 x 8 ft in section.
Prefabricated framing. To speed erection and reduce costs, prefabrication will be employed to a high degree for wall and floor framing. Exterior walls will be pre-assembled in units two stories high and at least 9 ft 9 inches wide. Field connections between panels will be made at points of minimum stress.
In a typical floor, open-web steel floorbeams generally will span from exterior to core columns, to provide column-free space at about the same cost as short-span conventional framing. Two or more beams will be preassembled with steel decking and erected as a unit, to save erection time. This floor system will be a space structure, with all elements, including the lightweight concrete floor slabs, participating in carrying loads. Its three dimensional behavior will permit large concentrated loads, such as law libraries, file rooms and safes, without requiring the usual strengthening of existing areas. And the open grid permits passage of ducts and piping, thus keeping story heights down without sacrificing stiffness in the floor system.
Clear span of the floorbeams is as much as 60 ft. They will be fabricated of high-strength low-alloy steels.
Walls resist wind. In designing the record-height towers against wind, Worthington, Skilling, Helle and Jackson adopted a scheme that does not rely on the core at all to take wind. Each tower will act as a vertical, cantilevered hollow tube. The giant Vierendeel trusses forming the loadbearing exterior walls will provide the required rigidity and strength to resist wind. All the horizontal shear will be resisted by the sides of the building parallel to the wind, and most of the overturning moment will be taken by the exterior walls normal to the wind. For economy in resisting the stresses, the wall columns will be made of high-strength steels, as indicated in the diagram above.
Floor warpage. Because of the great length of the columns, the difference in shortening of the exterior and interior columns under gravity loads could cause undesirable floor slopes. For example, a 1,400-ft-long column of A36 steel will shorten 8 inches under a design stress of 15,000 psi. The same column when made of heat-treated, low-alloy steel would shorten 24 inches under a design stress of 45,000 psi.
Assume that A36 steel is used for core columns and high-strength steel for wall columns and that these columns are not loaded until the entire structure is completed, a situation clearly not possible to achieve in practice. Assume further that each floor is constructed level. Then, after application of the load, at the top of the building the core columns will compress 8 inches and the wall columns 24 inches. Hence, the top floor will slope downward 16 inches.
But in practice, this extreme can't happen, because the loads go on the columns as the floors are completed. With each floor constructed level, there will be no differential shortening of columns and hence no floor slope at the top. The largest differential shortening will occur about 0.6 of the way up the building and be about 6 inches. Even this smaller floor slope, however, is objectionable.
To eliminate the undesirable floor warpage, WSHJ decided to design all the columns in each story for the same unit stress under gravity loads. The excess capacity of the exterior columns, then, can be used to resist moments and shears due to hurricane winds.
Over about half the building, steels in the yield-point range from 42,000 to 65,000 psi will suffice for the wall columns. In the lower portion of the building, heat-treated, low-alloy steels will be needed. At the base, where large columns can be used, a lower-yield-point steel will again be satisfactory.
The actual vertical-load stress to be used for each story will be determined from a consideration of costs for each column in that story.
Thus, the World Trade Center towers will have an inherent capacity to resist unforeseen calamities. This capacity stems from its Vierendeel wall system and is enhanced through the use of high-strength steels.
Fig. Framing plan calls for open-web steel beams spanning between closely spaced columns along the exterior and large, A36-steel columns around an elevator core.
April 2, 1964
PROBLEMS PLAGUE CONSTRUCTION OF NEW YORK WORLD TRADE CENTER
New York City's $575-million World Trade Center has been plagued by a conglomerate of natural and political obstacles since its inception. The worst winter and early spring weather in decades, and some of the most-difficult-to-work-On land ever built by God and men caused unavoidable foundation problems. A scramble of political blackmail and bureaucratic red tape, and the objections of individual and organized opponents ranging from bird lovers to TV networks made odds against success even more overwhelming.
Contractors and engineers have been breaking their hearts and, in some cases, their pocketbooks to get the center into and out of the ground. Despite the obstacles, which at this point seem at least as formidable as the center's twin 1,350ft-high towers will be when finished, considerable progress is being made, even though not much of it shows.
A World Trade Center was first proposed in 1960 to revitalize New York Harbor's declining role in world trade. Proponents also claimed that unification of all phases of world trade in a single complex would provide a big boost to the general economy of the metropolitan New York area.
To this end the Port of New York Authority (PNYA) planned the 10-million-sq-ft complex, which includes two 110-story towers and four low-lying buildings. Of the total area some 4 millon sq ft will be rented by firms engaged in foreign trade. The remainder, except for areas needed for population circulation, services and parking, will be used by U. S. and foreign governmental agencies.
The PNYA has already let more than $165 million in contracts for such things as foundations, elevators, structural steel, aluminum curtain wall panels, floor trusses and floor panels. But results won't be seen on the site for one, two or even three or more years, according to John M. Kyle, Jr., chief engineer of the PNYA, and Henry A. Druding, project manager.
On the site itself, only three major phases of the work are evident: utility relocation, demolition of existing structures, and installation of the cut-off walls that will surround the eight-square-block site from street level into rock some 55 to 75 ft below grade. All three operations are several months behind schedule, but in view of the obstacles, it is surprising that they aren't even further behind.
Since the Dutch founded New York as New Amsterdam, the shoreline has been extended more than 600 ft into the river by dumping every kind of fill imaginable to depths of about 35 ft. As a result, Martin S. Kapp, engineer of soils for the PNYA says the area is "suited more to an archaeological expedition than to foundation construction" (ENR 7/9/64 p. 36).
No one will agree more with this evaluation than Icanda Ltd. of Canada which has an $8.4-million contract to install cutoff walls around the 3,300-ft perimeter of the site. These walls, 3 ft thick and 55 to 75 ft deep, are being installed by the slurry method: the contractor digs a trench in sections to the desired depth, sustaining the walls by filling the excavation with a bentonite slurry that is later displaced with tremie concrete.
Icanda's methods are conventional, as is most of its equipment. But two special pieces of equipment, a rock slicer and a walking drill, are made necessary by the requirement that the cut-off wall be keyed 3 ft into rock.
New tools find tough diet. The rock slicer is a 90-ton monster with hydraulic controls that would do justice to a microscope. It consists of two 75-flong, cylindrical steel tubes mounted vertically at each end of a horizontal working beam. Beneath the working beam is the slicing blade-a knife-like piece of alloy steel, 3 ft wide, 3 ft deep. This blade, pushed downward in an arc by a hydraulic piston, cuts a 3-ft-deep slice out of the rock at each stroke. Through a rack and pinion arrangement on the working beam, the blade can be advanced from 1/16 to 2 inches at a time, depending on the hardness of the rock.
The slicer cuts the predominant Manhattan schist rock like cheese. It can take out one 1½ -inch thick, 3-ft-deep slice every minute. Intrusions of quartz, however, make it necessary to replace the rig with a percussion drill.
Because the rock slicer needs a hole into which to push the first slice of rock in each trench section, Icanda bought a specially built Hughes walking drill. It uses nine rotary cones, similar to those used in oil well work, and is powered by a diesel engine. This drives a pair of 10-piston, constant-speed, variable-volume hydraulic pumps, which in turn power the variable-speed, hydraulic motor that spins the drill.
The chassis of the machine comprises two frames, one above the other. The lower frame rests on rails laid on the ground; the upper frame rests, and slides, on the lower. When the machine must be moved, four hydraulic jacks, one at each corner, raise the upper frame which in turn raises the lower frame. Two almost-horizontal, hydraulic jacks linking the two frames then slide the lower frame 9 ft in either direction. When the lifting jacks are released and the upper frame rests on the lower, the horizontal jacks slide the upper frame along the length of the lower.
The Hughes rig not only drills holes for the rock slicer, but will also key the rock by drilling overlapping holes along the axis of the trench.
Big cages. Other noteworthy features of the cut-off walls are the 25-ton reinforcing cages that will go into them. Formed of high-strength steel (60,000psi yield strength), each cage contains 92 vertical rods set 6-inches c-c on each of the two faces to form a box 21 inches wide, 21 ft long and up to 75 ft high. Horizontal rods are also set on 6-in, centers. The cages are made lying flat and are set by a 150-ton crane using an 8-point pick-up at the upper end.
Spacers, to position the cage properly within the trench, are provided by 7-inch diameter concrete wheels threaded on horizontal rods before they are wired on. These wheels, set 4 ft on centers both vertically and horizontally, are free to roll on their rebar axles as they contact the side of the trench while the cage is lowered.
The cages include insert ports through which tie rods will be placed to anchor the wall to rock outside the excavation area, making internal bracing unnecessary.
In spite of special equipment and experience in the slurry method, Icanda is behind schedule. Weather is partly to blame-five major snowstorms, the last leaving 10 inches of snow on the first day of spring, have not helped.
But the real problems, according to Icanda's project manager, Michael Petrone, are caused by obstructions encountered in the upper 35 ft of digging.
Icanda facilitates trenching operations with a wide trench 10 ft deen. This is backfilled with a lean (one bag) concrete and the trenching buckets work through this.
Obstructions to progress. Obstructions, below the 10-ft level are still legion. Vertical piles are easily pulled out by the trenching bucket; horizontal timbers perpendicular to the trench have been a real headache. It took Icanda two shifts to chew through one 2 x 2-ft oak timber. It took three shifts to get through a laminated timber deck.
Oddly enough, the most troublesome obstruction is the easiest to remove. It is the 10 to 15-ft-thick layer of small ballast stones dumped over the side of sailing ships when the river covered what is now the job site. The stones are no problem for the bucket, but those adjacent to the trench area continue to roll into the cut, causing tremendous overbreaks. In one section the overbreak was 85 %, according to Arturo Ressi d. Cervia, Icanda's field engineer.
Because Icanda must provide an on line, relatively smooth inside wall, overbreaks cannot be filled with regular 6,000-psi wall concrete. The projections would be too difficult to remove.
To lick the problem, Icanda fills the entire area, trench and overbreak, with a one-bag concrete. When this has set up, the contractor redigs the trench through the lean concrete. The material outside the wall will stay in place to stabilize the soil; the lean concrete inside will easily spall off the good concrete in the wall.
THE BATTLE ROUND BY ROUND
Opponents of the World Trade Center have launched strong campaigns against it whenever and however money and the law will permit. Major obstacles were raised by the State of New Jersey, which by law has to approve PNYA activities, and by the City of New York itself. And almost 600 small businessmen and residents of the area, threatened with dispossession, joined with people interested in the Empire State Building, who covet its long reign as the world's tallest building, to fight the center in both the courts and in the press.
When the project was first approved in 1961 by the New York State legislature, the proposed site was on Manhattan's lower east side.
Not until after the PNYA agreed to move the center to the west side of the city, facing the Hudson and New Jersey, did the New Jersey legislature give its approval-and even then it required the authority to operate and rehabilitate the badly rundown Hudson Tubes and Manhattan Railroad, which carry 28 million passengers annually between New York and New Jersey.
Then the city got into the act. Original negotiations between the Democratic Wagner administration and the PNYA apparently resolved most, if not all of the major authority-city relationships-but not in writing. When the Liberal-Republican administration of Mayor John Lindsay took over, the picture changed.
The Republicans inherited a city loaded with debt and short on revenue. The multibillion-dollar PNYA seemed a logical source of relief. City officials cited the city's potential loss of tax revenue and the need for increased services resulting from the center's erection and demanded astronomical payments from the PNYA as the price for permission to build. (At one time these payments totaled some $3 billion to be paid over a period of 99 years.)
Give and take-Disputes between the city and the PNYA are largely (though not completely) resolved. After the center itself, the largest single boon to the' city will be construction of a 23.5-acre landfill extending from the pier-head line to the bulkhead line in the Hudson River adjacent to the site.
The PNYA will supply the landfill from the 1.1 million cu yd of material to be excavated for the center's foundations under a $4.4-million contract. This concession is hardly a total loss to the authority. Without the landfill, a good part of its cost would be spent on long-distance truck hauls or rehandling for barge removal of the spoil from the city.
Among the other agreements by the PNYA: payments to the city of $1.7 million annually during construction, in lieu of taxes previously received from private owners; payments amounting to about $6.7 million annually after completion (this figure is subject to adjustment to keep it in line with taxes that would be paid by private developers of similar properties); about $7 million in area improvements such as street widening and straightening.
With the city satisfied, construction started at the site on August 5, last year. First project was installation of two telephone vaults in West St., directly under the elevated West Side Express Highway and over the tubes that carry Hudson & Manhattan trains under the river. This work is virtually complete. Demolition, started piecemeal during bouts with the city, was stepped up and at the present time is about 50% complete. More than two-thirds of the site's former tenants have already been relocated by the authority.
Even with construction under way, sporadic attempts to halt the center are still being made. Recently, TV interests protested on the grounds that the towers will interfere with reception in many local areas. In answer, the PNYA offered to allow the networks to put their antennas on the towers, rent free until current leases on the Empire State Building expire.
Fig . Site of World Trade Center is partially cleared. Piers in foreground will be replaced by 23.5-acre landfill.
Fig . Workmen tremie concrete into trench to displace slurry that holds the cut during excavation.
Fig . Trenching rig is digging 65 ft deep for cutoff walls that will encircle the 16-acre site.
April 13, 1967
RECORD HYAC CONTRACT LET FOR WORLD TRADE CENTER
The Port of New York Authority's World Trade Center has produced another in its series of superlatives-the largest contract ever for heating, ventilating and air-conditioning work.
A contract for $38,670,000 went last week to a joint venture of H. Sand & Co. and Courter & Co., both of New York City, for provision and installation of HVAC equipment in the two 110story towers.
The work will involve some 100,000 supply and return air-conditioning outlets to be integrated with interior lighting fixtures and 24,000 under-window induction units.
The combined air-conditioning capacity of the two towers calls for 32,000 tons of refrigeration with continuous filtration and cooling of 8 million cu ft of air per minute for circulation.
Chilled water will come from a subgrade refrigeration plant being installed under separate contracts. Water pumped from the nearby Hudson River will make the installation of a cooling tower unnecessary.
June 27, 1968
EMPIRE STATE BUILDING'S 33-YEAR-OLD RECORD TO BE TOPPED:
TWIN TOWERS TO GO 110 STORIES
Twin towers 110 stories high planned for the World Trade Center in New York City will become the world's tallest buildings. They will top the present record-holder, the 1,250-ft Empire State Building (excluding the TV antennas on top), by 100 ft.
The Port of New York Authority will build the trade center to provide offices and exhibit areas for government agencies, trade services and private businesses concerned with exports and imports. The structures will contain about 10 million sq ft of rentable floor area. Construction cost is estimated at $350 million.
Construction is expected to start early next year. The first stage, one tower and some of the low buildings, will be completed in 1968, the remainder of the project during 1969 and 1970.
The project will occupy a 16-acre site along the Hudson River in downtown Manhattan. Its record-breaking skyscrapers will rise from a group of low buildings surrounding a five-acre plaza with reflecting pools.
The twin towers will soar to a height of 1,350 ft. Each will be 209 ft square and will be designed to resist wind mainly through the structural arrangement of the outer walls. The buildings will act under wind load as vertical, cantilevered, hollow tubes with walls composed of Vierendeel trusses.
The buildings will be designed for a 45-psf wind load. Studies are being made to insure both low sway and low acceleration under this load.
Exterior walls will serve architectural and structural functions (see p. 54). In addition to taking the wind load, they will support not only their own weight but the floors as well. Steel box columns about 14 inch square will be spaced 39 inches c-c in the outer walls and windows will be set between them. Thus, the windows, extending between spandrel beams, will be long and narrow.
The column and spandrel covers have not yet been selected. Consideration is being given to stainless steel or aluminum sheet laminated to precast concrete and to aluminum panels.
Rentable space in the towers generally will be free of columns. Floor-beams will span 60 ft or more between the exterior columns and steel columns in the walls around the elevator core. Corner columns at the base of the core may be solid steel as large as 2 x 8 ft in section.
Low-rise structures will be founded on bearing piles or caissons carried to rock about 70 ft below grade. The skyscrapers and other buildings with deep basements will be supported on concrete piers resting on bedrock.
The PNYA engineering department is considering a novel method of retaining the excavation. Before general excavation starts, a slurry-filled trench will be built around the project and then filled with concrete to form a cutoff wall. Constructed in short segments, this wall will be keyed into the rock to prevent intrusion of water and soft ground. The wall will be anchored with prestressed ties to the rock.
The Trade Center will be served by 230 passenger elevators. The towers will incorporate an unusual elevator system to maintain a high ratio of rentable floor area to vertical-transportation area.
Each tower building is divided into three zones, one above the other. The first extends from the first to the 40th floor, the second from the 41st to the 73rd floor, and the third from the 74th to the 110th floor. Each zone will be served by 24 elevators, arranged in four banks of six each. But upper-zone elevators will not serve the ground floor.
Instead, 55-passenger express elevators will speed at 1,700 feet per minute, from ground level to the 41st and 74th floors, where transfer lobbies Will be provided. The lower "skylobby" will be served by 11 express elevators, the upper one by 12.
Also included in the Trade Center will be a 250-room hotel and a new Manhattan terminal' for the Port Authority Trans-Hudson system, the former Hudson and Manhattan Railroad. It carries over 28 million passengers a year between New Jersey and New York City. The pew terminal will replace. outmoded facilities nearby.
Underground passageways will connect every subway: system in lower Manhattan with a concourse beneath the Trade Center plaza. High-speed moving stairs will connect the air-conditioned concourse with street level.
Large areas below grade will be. assigned to U.S. Customs examination and cargo pickup. Also below the plaza will be tenant storage areas, five parking levels for 1,600 automobiles, and mechanical and refrigeration equipment. The project will require 40,000 tons,' of refrigeration for air conditioning.
At ground level, sheltered. archways will form galleries' around all. four sides of the plaza. These glassed-in, air-conditioned spaces will house offices.
Minoru Yamasaki and Associates, Birmingham, Mich., and Emery Roth & Sons, New York City, are the Architects. Worthington, Skilling, Helle and Jackson, of Seattle, are, the consulting structural engineers; Jaros, Baum and Bowles, of New York City, the consulting mechanical engineers; and Joseph R. Loring and Associates, New York City, the consulting electrical' engineers. These firms were assisted in the design by the World Trade Center Planning Division under the direction of Malcolm P. Levy, and the PNYA engineering department, John M. Kyle,' chief engineer.
Fig . World Trade Center's towers will rise 1,350 ft in New York
Fig . Proposed skyscrapers will dominate the skyline of downtown Manhattan.
Fig . Floorbeams will span from exterior columns to elevator-core walls.
Fig . Structural consultant John Skilling.
Fig . Architects Richard (left) and Julian Roth and Minoru Yamasaki.
January 23, 1964
NEW YORK GETS $90 MILLION WORTH OF LAND FOR NOTHING
A three-sided box of cellular cofferdams and spoil from the World Trade Center foundations are giving New York City 23 acres of what may be the least expensive, but most valuable land in the country. The land is being reclaimed by the Port of New York Authority from the Hudson River right next to Manhattan's financial district.
The actual value of the new land will depend largely on its use, but it is in an area where vacant land is nonexistent and where land that has to be cleared of old buildings sells for thousands of dollars a front inch. Consequently, some estimates put the value of the new land to the city at as much as $90 million.
And it is costing the city nothing. Its creation results from an overall agreement that cleared the way for the Authority to erect the $575-million World Trade Center.
The city is not the only beneficiary, however. PNYA has undoubtedly saved hundreds of thousands of dollars in excavation costs and a considerable amount of time as well. Excavation for the center will run close to 1.2 million cu yd. Without the landfill as a spoil area the contractors would have to truck the spoil to riverside for loading on barges that Would carry it out to sea, or truck it 10 to 12 cu yd at a time to the Jersey meadows, 8 to 19 miles away. Either process would be at least as expensive and certainly more time consuming than hauling the material directly to a spoil area adjacent to the site, and would provide no financial return.
Since the landfill is directly connected with the foundation excavation of the trade center it was almost necessary that STEEL SHEETS form cellular cofferdam. SAND DUMPED in cofferdam cells was barged from Long Island Sound. the work be done by West Street Associates, prime contractors on the foundations. This combine consists of Slattery Associates, Inc., Gull Contracting Co. Inc., Poirier and McLane Corp., Tully & DiNapoli, Inc. and Spencer, White & Prentis, Inc., all of New York City. Consequently, PNYA awarded a $4.4-million contract for the work to WSA.
Because all the members of the combine are primarily land contractors the group sublet the marine work on the landfill to a joint venture of Horn Construction Co., Inc., of Merrick, N.Y., and Spearin Preston & Burrows, Inc., of New York City.
The fill projects about 700 ft into the Hudson from the existing shore line and is 1,484 ft long, about six city blocks. Enclosing the reclaimed area are cellular cofferdams made up of some 8,500 tons of steel sheetpiling. There are more than 7,800 individual sheets ranging from 56 to 64 ft in length set into 40 cells, each 64 ft in diameter.
Clearing the way. Before the cofferdam work could be done, the old piers, ferry slips and head houses had to be removed. This was no small task and Horn-Spearin subcontracted it to Wrecking Corp. of America, of Long Island City, N.Y. Each of the piers contained 1,600 to 2,000 piles. In the outshore end and in the areas of the cofferdams, the contractor had to pull the old piles. In the area within the cofferdam he had to cut or break them off at the mud line.
Disposal of the waste material was also a problem. Initially the contractor loaded it on small barges and towed it into lower New York Bay to be burned. This became an air pollution issue, however, so the contractor arranged to have the material loaded on larger burning barges that could take the old wood 20 miles out to sea.
Because of tidal flow there is little silting near the east bank of the Hudson. However, to insure the integrity of the cofferdams, PNYA required that on the long line of cofferdams, the bottom of the river be dredged 10 to 12 ft deep for a width of 114 ft and the area filled with sand. This work was handled by Great Lakes Dredge and Dock Co., of New York City.
Great Lakes used three dredges, two clamshells and one dipper stick. The spoil was dumped at sea and the sandfill was brought in from Long island Sound in bottom-dump barges.
Floating templates. For accuracy in setting sheets for the cofferdam cells, Spearin's project manager, Thomas Sullivan, decided to build six unusual templates on the site. They are made of structural steel and weigh 20 to 25 tons each. Each one has 56 oil drums strapped under its top frame to keep it afloat.
According to Sullivan, the buoyancy of the templates saved a lot of grief. It made it possible to move the frames around easily and made it unnecessary to compensate for tidal action when they were being set.
The templates are about 63 ft in diameter and 16 ft high. Horn-Spearin floated each into place, checked its location by triangulation then set a 12-inch diameter spud in one of its four 16-inch spud wells. After rechecking location the contractors placed the other three spuds and drove them into soft rock. Next, they raised the template so that the flotation barrels were about 2 ft above high water and held it in place by sliding 2-inch pins through it and the spud piles.
Instead of driving the sheets in succession around the perimeter of the template, the contractors first set and drove tee sections that would link with the diaphragms between cells. After these were tack-welded to the template, the sheets were set between them. For the most part, cells were installed on a weekly cycle; with three crews, the contractors averaged three completed cells a week.
Horn-Spearin found early in the job that heavy hammers damaged the piles so they used 8,250 and 8,750-ft-lb double acting machines. To hold the sheets against the template while they were being set, Sullivan used a come-along on a cable wrapped around the template outside the sheets. He didn't drive any of the sheets (except the tees) until after all of them were set. To guide the diaphragm sheets Sullivan used a shallow curved template welded to the tee pieces.
As each cell was finished, the contractors filled it with 5,500 to 6,000 cu yd of sand-seven barge loads. Using 2½ to 4-cu-yd buckets, Horn-Spearin unloaded a barge in about six hours and filled a cell a week with each machine. Since he had three rigs setting steel and three filling cells and each completed its work on a cell every week, he maintained a balanced operation.
West Street Associates started filling the area as soon as there were enough cells inshore to contain the spoil. The contractors expect to turn the completed fill over to the city by mid-1969.
April 18, 1968
Fig . Dilapidated piers extend from Manhattan into Hudson River before excavation started for World Trade Center (arrow).
Fig . Cellular cofferdams, filled with sand, outline the 23-acre landfill being built by the Port of New York Authority.
Fig . Cell template goes Into the river.
Fig . Cofferdam templates were assembled on old pier at landfill site.
TRADE CENTER COMES INTO FOCUS
Only a few months ahead of the construction start, architect Minoru Yamasaki has delivered a refined design for the $525-million World Trade Center to the Port of New York Authority.
The center's twin 110-story super-skyscrapers now rise cleanly from side-walk level. What was a site-encircling podium building in an earlier concept is now four separate 10-story buildings distributed about the circumference of the 16-acre site.
The reason for the change is to give maximum attention to the two world's tallest buildings and to improve pedestrian circulation through the whole center.
Mr. Yamasaki also created new facades of dark gray concrete for the four low buildings that make them more contemporary and suits them better to New York's dirty atmosphere. The U.S. Customs will rent one of the four buildings; another will be a hotel-information center; the remaining two will be rented as commercial space.
Either aluminum or stainless steel will clad the tower walls in gleaming contrast to the low buildings.
The plaza, too, has changed character. Off-center concentric circles, like those of the Campidoglio in Rome, and a paving design related to the towers will line its surface. Instead of lagoons (often just refuse collectors in a city) bordering on the low buildings, small courts richly landscaped will dot the five-acre plaza, with an 80-ft diameter pool and fountain at its focus. The Port Authority hopes to make the center a tourist magnet like Rockefeller Center and expects to attract 80,000 tourists a day.
The primary entrance to the Trade Center remains, but the new design opens the plaza to streets on the north, south and west sides. The west entrance opens the center to the Hudson River waterfront, scheduled for development after the elevated West Side Highway is depressed, as presently proposed by the New York City Planning Commission.
Among the things awaiting final design are a communications system to direct 50,000 workers through the center and $2 million to $5 million worth of sculpture and other art.
Demolition of the properties on part of the 16-acre site will begin in a few weeks for the project Mr. Yamasaki once called "the most exciting thing we or anyone else in the architectural profession will have the opportunity of working on for a long time to come."
Prospective occupants must agree. With project completion five or six years away, 75 % of the center's space has already been committed.
Three buildings on the site have already been razed for pile-load tests (ENR 9/23/65 p. 29), and 26 others are vacant and awaiting the headache ball. With the few changes in plans completed, construction will begin right after the razing-probably in a couple of months. The new design is not expected to alter the $528-million cost.
Mr. Yamasaki's Birmingham, Mich., firm is associate architect with Emery Roth & Sons, New York City.
March 24, 1966
Fig . Towers will no longer abut low buildings.
CONTRACTOR IS CONSULTANT ON WORLD TRADE CENTER
The Port of New York Authority last week named Tishman Realty & Construction Co., of New York City, as consultant-contractor for its twin-tower, 100-story World Trade Center in downtown New York.
Port Authority spokesmen say Tishiman will receive an estimated $250,000 for its services over a 16-month period. Under this agreement, Tishman will review all the contract documents before they are released for bidding and assist the Port Authority in establishing cost estimates, construction timetables and material supply schedules.
Tishman's appointment as consultant-contractor does not mean that the company will be general contractor for the over $500-million project, says the Port-Authority. Nor does it mean they will not.
Tishman's experience as an owners builder in many cities across the country has led to several recent contracts as construction consultant on large building projects.
Currently the firm is consultant contractor on the Madison Square Garden complex in New York City and the 100-story John Hancock office and apartment building in Chicago. Besides its duties as consultant on these two jobs, Tishman is general contractor for the entire John Hancock project and for the office portion of Madison Squares Garden.
March 3, 1966
FEWER SURPRISES will turn up in the construction of the World Trade Center because the owner of this proposed world's largest office complex has hired one of construction's new breed, a contractor-consultant (p. 15) - The $250,000 that the Port of New York Authority will pay Tishman Realty and Construction Co., of New York City, for 16 months' worth of its expertise may turn out to be the best money spent in constructing the 10-million-sq-ft center in lower Manhattan, even though PNYA already has a design team of top architects and engineers. For nobody knows field construction like a contractor. If he is good, he has prices, material delivery times and all the techniques of scheduling and construction at his finger tips. The Port Authority's and its contractors' paths through this $525-million construction project are certain to have fewer surprises.
March 3, 1966
TRADE CENTER STEEL CONTRACTS LET
All of the steel erection and much of the steel for the World Trade Center's twin 110-story towers were included in contracts totaling $74,079,000 awarded last week by the Port of New York Authority.
Of the six contracts, five involved the steel fabrication and erection. They represented a second go-around on the steel for the 1,350-ft skyscrapers, to be the world's tallest. The Port Authority initially sought to have the steel fabricated and erected under a single contract. Last August it received proposals from Bethlehem Steel Corp. and United States Steel Corp. These proposals were rejected as too high, and the job subsequently was broken up into packages in an effort to get a lower price.
Price of the big two's rejected offers were not disclosed. But the Committee for a Reasonable World Trade Center, a gadfly critic of the project, in a full-page newspaper advertisement last October said that the rumored low bid for the steel was more than $650 per ton, compared with authority estimates of $400 per ton. The same advertisement said the rumored requirement was 220.000 tons as against an estimated 180,000 tons.
The Port Authority spokesman declined comment on its critic's figures. However, PA Chairman S. Sloan Colt said that contract costs so far, including the newly awarded contracts, are $6.5 million below corresponding estimates in the recent raised $575-million project cost estimate.
The steel contracts awarded:
In addition, officials awarded a $210,000 - 250,000 contract to the Aluminum Company of America, Pittsburgh, Pa., to fabricate and erect the towers' aluminum curtain walls. Alcoa will assign the work to Cupples Products Corp., St. Louis. The contract includes 43,600 windows with 620,000 sq ft of glass and vermiculite plaster fireproofing on the interior face.
- Fifty-five thousand tons including all exterior steel (columns and spandrels) from the ninth floor to the top-Pacific Car & Foundry Co., Seattle, Wash., $21,790,000.
- Erecting the entire 192,000 tons of structural steel in the twin towers and the center's subgrade area-Karl Koch Erecting Co., Bronx, N.Y., $20 million.
- Floor system-Laclede Steel Co., St. Louis, Mo., floor space trusses and miscellaneous steel, $6,650,000; Granite City Steel Co., Granite City, Ill., steel deck and power and telephone ducts, $1,889,000; arid Karl Koch Erecting Co., assembly and delivery of the deck panels combining the two components, $2.5 million.
The towers' exterior columns are spaced at 40 inches c-c. They are 14-inch square hollow box sections, linked by 54-inch deep spandrels, and forming giant Vierendeel trusses in each wall face.
To maintain uniform column and spandrel dimensions, structural engineers Worthington, Skilling, Helle & Jackson, of Seattle, specified a variety of steel strengths and sections to resist varying stresses throughout the frame.
There will be 12 different steels, ranging from A36 with a 36,000-psi yield strength to heat-treated steel with a yield of 100,000 psi.
Pacific Car & Foundry will pre-fabricate the wall elements in 5,828 panels, generally 10 ft by 36 ft, with the heaviest panel weighing 22 tons. Because of the exterior's key structural role, fabrication will require closely controlled and involved welding procedures.
Clear span of the 33-inch deep floor trusses, to be fabricated of high-strength, low-alloy steels, will be as much as 60 ft from the exterior columns to the core columns. Two or more will be preassembled with steel deck and erected as a unit. Corrugated metal formwork at the top chord will permit pouring the floor slabs without additional formwork.
The Koch firm plans to use specially designed equipment on its job. Erection is to begin about July, 1967, with the work taking 31 months.
Last week's awards brought contracts to date on the center to nearly $150 million.
February 2, 1967
Fig . Fabricated wall and floor elements will speed erection of 1,350-ft towers.
WORLD TRADE CENTER HVAC SYSTEM IS PROJECT'S HIDDEN FEAT
Even though everyone for miles around New York City will be able to see the twin 1,350-ft-high World Trade Center towers glistening in the sun, most persons will never see the product of the largest single contract in the $700-million project. But everyone entering the complex's buildings will be more comfortable because of the $41-million contract that covers the trade center's HVAC systems. The systems will circulate and filter 9 million cu ft of air per minute to serve more than 9 million sq ft of office space.
The owner, the Port of New York Authority (PONYA), says the $41 million, awarded to a joint venture of Courter & Co., Inc., and H. Sand & Co., Inc., both of New York City, represents the largest HVAC contract ever let. Its size is due, of course, to the height of the buildings, but also adding to the loads on the system are four low-rise buildings in the complex, a concourse below a central plaza, and a subway station, the first ever to be air-conditioned (ENR 7/8 p.1 1). The air conditioning system's heart is a 2.5-acre underground refrigeration plant. For heating, PONYA will buy steam from the city's public utility.
Located at the fourth basement level, the refrigeration plant receives cooling water from the Hudson River, which is just west of the project.
When PONYA engineers and consulting mechanical engineers, Jaros, Baum & Bolles, New York City, looked at the problem of air conditioning the identical towers and other areas, they considered conventional cooling towers rising from a refrigeration plant, along with supplemental cooling towers at various levels in the structures. But because the Hudson River is within 150 ft of the site, the engineers decided to construct the underground plant and run the intake and outflow pipes to the Hudson. The engineers' added incentive for eliminating the cooling towers was the great amount of space they would consume and the towers' negative esthetic effect on the project.
The $6.2-million plant is centrally located between the two towers. It will serve the towers, an eight-story U.S. Customs Building, two nine-story office buildings, a hotel whose design is not yet complete, and a 400,000-ft-square subplaza concourse. Mechanically, the entire complex is divided into two zones: the high zone, which covers the towers starting at the 59th floor, and the low zone, which takes in the lower tower floors, the low-rise buildings, and the subplaza concourse.
Double-shell unit. During the design stages, engineers' calculations showed that the upper zone required 17,000 tons of refrigeration and the lower zone 32,000 tons, for a total of 49,000 tons. Normally, eight refrigeration machines would be used: two 7,000-ton units and one 3,000-ton unit for the high zone and four 7,000-ton units and one 4,000- ton unit for the low zone.
However, PONYA engineers and the York Division of Borg-Warner Corp., Chicago, supplier of the units, came up with a double-shell unit design that serves both the high and low zones with the required capacity, thus reducing the required number of units to seven.
A shell is a heat exchanger in the shape of a cylinder through which copper tubing runs. Refrigerant gas surrounding the tubes extracts heat from the water that flows through the tubes. The total surface area of the tubes is proportional to the capacity produced.
Says Frederick DiPaolo, PONYA mechanical projects administrator, "By using the dual-shell design, we have a single 7,000-ton unit that provides 3,000 tons to the high zone and 4,000 tons to the low zone. We've eliminated one unit but another advantage of the design is that all critical parts are the same except for the two shells."
Hudson pump house. Located on land fill on the east shore of the Hudson, a pump house will provide the refrigeration plant with 90,000 gpm.
When the refrigeration plant is in operation, 10 pumps will pump chilled water to all mechanical equipment rooms, called MERs, in the structures. The MERs run from the seventh to eighth floors, 75th to 76th and the 108th to the roof in each tower. The levels below the plaza and the low-rise buildings have their own mechanical rooms. In the towers, the MERs serve 16 floors above and 16 floors below their location with three HVAC systems. The peripheral system covers the perimeter and 15 ft of interior space; the interior system serves the area from the 15-ft mark to the core; and the core system supplies the core and elevators.
Tying all of the trade center's systems together is a computer that will receive data from 6,500 sensors that monitor temperatures, pressures, power input, humidity, and chilled water flows. The computer has 2,100 alarm contact points to pickup any malfunction.
"With the computer, a single operator can detect a problem and shut off or turn on any system on any floor," says DiPaolo. "The whole system is on a 365-day program that shuts down appropriate systems at the end of a day, on weekends and during holidays. But if one tenant wants his space served after working hours, it can be done by pushing a few buttons."
The computer is located adjacent to the refrigeration plant. If anything goes wrong in any of the systems, a light goes on at the console and a schematic of the key system involved appears on the console monitors. A high-speed typewriter prints the number of the trouble point, which then can be located on the schematic.
Also tied to the computer is the smoke detection system. If smoke is detected, its location will be shown by lights on the console. An audible alarm is also sounded. A remote unit shuts down the fans in the area of the fire and the operator at the console turns on the fans that will be required to exhaust the smoke-filled areas.
December 23, 1971
Fig . Cooling plant covers 2.5 acres.
Fig . Equipment serves 32 floors.
WORLD TRADE CENTER KEEPS GETTING MORE EXPENSIVE
The Port of New York Authority last week said its World Trade Center in New York City's lower Manhattan will cost $575 million, a jump of 9.5% from the $525-million estimate announced in 1965 (ENR 9/23/65 p. 29). Four years ago the cost was pegged at $270 million.
The estimate subsequently went to $350 million, and in 1965 rose again to $525 million (ENR 9/23/65 p. 29). The organized opposition to the center, the Committee for a Reasonable World Trade Center, says even the new estimate is too low. Lawrence A. Wien, committee chairman and head of the syndicate that owns the Empire State Building, says the center will cost a minimum of $750 million. Others believe its cost could top $1 billion.
The trade center will consist of twin-towers each 1,350 ft high, exceeding the Empire State Building in height by 100 ft.
So far, the authority has spent or obligated $140 million of the estimated cost, the most recent spending commitment totaling $62.2 million-$35 million for elevators and escalators, $18.7 million for excavation and $8.4 million for a 3,100-ft foundation retaining wall (ENR 11/24/66 p. 7).
Last year, the authority received proposals for the 185,000-ton structural steel contract (ENR 8/11/66 p. 64), but no award has been made yet.
Wien questions the steel estimates, saying the towers require 220,000 tons, and that rumors put the proposed prices at $650 per ton, not $400 a ton as estimated by the authority's staff. The authority neither denies nor confirms Wien's charges.
January 5, 1967
TRADE CENTER MAY LOSE BIG TENANT
The Port of New York Authority's claim that it will have no trouble in renting the 10 million sq ft of the World Trade Center is based on a New York State commitment that would make it the principal tenant of the $575-million complex. Last week that commitment came under scrutiny.
State Comptroller Arthur Levitt (D.) said he is studying whether it would be cheaper for the state to build its own office building at either the Brooklyn Navy Yard or the Brooklyn Army Terminal than to rent space in the 110-story, twin-tower trade center. Both federal reservations have been turned over for disposal.
Gov. Nelson A. Rockefeller (R.), in an arrangement that made it possible for the Port Authority project to go ahead, three years ago said that state offices in New York City, which occupy 2 million sq ft in 35 locations, would be centralized in the trade center.
Levitt says, however, that the state cannot sign a valid lease without his approval. He is awaiting results of a cost study to help decide whether to give approval. "The basic policy decision of whether the state ought to have its office in a trade center is up to the governor. But the cost factor is a very important consideration," said the comptroller, who is an elected official.
"I'm not suggesting that I would withhold approval arbitrarily but I regard the responsibility to approve as a very important one, and I'll only make a decision after we have all the information."
January 12, 1967
COST PLUS PLENTY TISHMAN GETS TRADE CENTER JOB WITH A $3.3-MILLION FEE
The Port of New York Authority's construction committee this week recommended that the agency hire Tishman Realty & Construction Co., Inc., of New York City, as general contractor for the $575-million World Trade Center in lower Manhattan. Tishman would receive a fixed fee of $3,250.000, plus reimbursement of direct field costs, now estimated at $16 million.
Tishman has been involved with the project almost from its conception. In April, 1964, the authority hired Tishman, Diesel Construction Co., George A. Fuller Co. and Turner Construction Co., all of New York City, to review independently construction techniques planned for the two 110-story towers of the trade center (ENR 4/16/64 p. 19). For this each received $15,000.
Last year, Tishman was named "consultant-contractor" for the project at a fee of $250,000 (ENR 3/3/66 p. 15). In this capacity, the company reviewed all contract documents before they were released for bidding and also assisted the Port Authority in establishing cost estimates, construction timetables and material supply schedules.
James C. Kellogg III, vice chairman of the agency, said Tishman will "begin immediately to coordinate and supervise construction and assume responsibility for all field contracts exclusive of the foundation work. Subject to authority approval, the company also will arrange for all remaining subcontracts."
So far, the authority has awarded contracts totaling about $165 million, including those for the foundations, elevators and escalators, fabrication and erection of most of the 192,000 tons of steel, and the fabrication and erection of aluminum curtain walls.
Contracts still to be let include electrical, mechanical and finishing work for the tower buildings, two plaza buildings, an information center, hotel and sub-grade areas.
The twin towers will rise 1,350 ft above an open, five-acre plaza surrounded by four low-rise structures.
Kellogg said the committee made its recommendation to the full board of commissioners after considering proposals from Tishman, Fuller and Turner.
Tishman holds the general contract for the 100-story John Hancock Center in Chicago, and is construction consultant for the Madison Square Garden Sports and Entertainment Center on the site of Pennsylvania Station in New York City.
March 2, 1967
WORLD TRADE CENTER NOW TOPS TALLEST BY 4 FT
On Monday, Oct. 19, at 2:51 p.m., New York City's World Trade Center became the tallest skyscraper in the world, reaching a height of 1,254 ft and surpassing the Empire State Building by 4 ft.
A 10-ton, three-story-high wall panel, consisting of three box columns and three spandrel girders, was the first section of the 103rd-story level to be lifted into place on the north tower. When completed, 5,828 panels will compose the two 110-story, 1,350-ft-high towers, topping the Empire State Building by 100 ft.
Initial occupancy of the lower floors of the north tower is planned for the end of this year. The Port of New York Authority is building the $600-million project.
In Chicago, work has begun on the Sears, Roebuck & Co. headquarters, which will be 100 ft taller than the World Trade Center. About 40 years ago the Empire State Building passed the Chrysler Building in New York City to become the world's tallest at 1,250 ft.
October 29, 1970
Fig . North tower looms over lower Manhattan.
ALUMINUM SKIN SHEATHS WORLD'S TALLEST TOWERS
When the first tenants move into the 110-story north tower of New York City's World Trade Center near the end of next month, the building won't be finished. It will, however, be just about completely clothed in its permanent silver-toned aluminum sheath and most of its windows will be glazed. The wall panels have been raised to the 68th floor and they are going on and up at the rate of four to five floors a week.
As in any well run job, rapid progress stems from many things including competent long-range planning, good management and coordination and cooperation among designers, suppliers, owners and contractors. For the Trade Center wall panels, the extensive use of specially built castings, jigs, templates and machines speeds up the job. One casting permits a four-man crew to set a wall panel accurately in minutes. Job and shop-built templates and jigs enable one and, at most, two-man crews to set and attach quickly and precisely every component in the wall system, with no one holding the pieces. There is one precision machine that drills a dozen 9/16-inch diameter holes through 1 3/8-inch high-tensile steel in 45 to 50 seconds. Another rapidly and safely sets exterior wall panels from inside the building.
The World Trade Center is being built on a 16-acre site in downtown Manhattan by the Port of New York Authority (PONYA) at a cost of about $650 million. The work is under the direction of PONYA field construction manager Rino Monti. The project will include four eight-story buildings and two 100-story towers, which for several years, at least, will be the highest in the world at 1,350 ft. (Sears, Roebuck & Co. has started work in Chicago on a 100-story structure that will top the Trade Center towers by 100 ft. The Trade Center, however, from the stand-point of area, mass volume and complexity will exceed anything now planned, including the Sears Building. The Sears Building will have 3.7 million sq ft of usable space. The World Trade Center project will have more than 9 million.)
The center rises from what is undoubtedly the world's biggest basement. The foundation walls go 70 ft below ground and they have a perimeter of 3,350 ft. When completed, probably in 1973, the center will provide 320 acres of working space for 50,000 persons and will receive an estimated 80,000 visitors daily.
Heavyweights. The two towers alone will weigh more than 1 million tons. Contributing to this weight will be more than 200,000 pieces of structural steel (some weighing up to 54 tons each), 208 high-speed elevators, 50,000 telephones, 7,000 plumbing fixtures and 40,000 doors.
But of all the components, none will be more conspicuous than the 43,600 aluminum curtain wall panels that cover the exterior structural steel and support more than 43,000 narrow, bronzed-glass windows.
Because of the great height of the structures and the relative flatness of the surrounding territory, the panels may be seen glistening in the sun from almost anywhere within a 5,000-sq-mile area. Visibility will extend from past Jones Beach (on Long Island) on the east to the Delaware Water Gap (between New Jersey and Pennsylvania) on the west. On the north-south axis, visibility will extend from Asbury Park on the central New Jersey shore to New York's Bear Mountain on the west side of the Hudson River, near West Point.
The column covers, which are the major part of the wall system, are U-shaped, 12 inches deep, 18 inches wide, and for the most part 12 ft long. They are made of .09-inch thick anodized aluminum sheets and weigh about 100 lb each. Each consists of four parts: the main sheet, two jamb pieces (which take the glass and the horizontal spandrel covers) and a stainless steel track that will accommodate an automatic window washing machine capable of cleaning and drying seven floors of windows per minute.
There are also some almost unnoticeable, atypical cover sections at the ninth floor and at the mechanical floors. The most spectacular of the atypical sections, though, are the huge, three-tined tree covers that encase the lower floors. These are up to 72 ft high, 10 ft wide at the top and weigh about 3,500 lb each (see picture p. 40.).
The entire wall covering system is designed for pressure equalization, mainly to prevent water from being drawn in through joints in the covers into the interior of the walls. To accomplish this, every vertical panel has a horizontal baffle at the top and every 10th spandrel cover has a vertical baffle.
A $21-million contract covers the supplying and installing of the curtain wall system, which includes about 9 million lb of aluminum castings, extrusions and sheets. The contract includes fireproofing of the exterior columns and the installation of about 620,000 sq ft of bronze-tinted glass.
Cooperative effort. Aluminum Company of America (Alcoa) supplies all the aluminum, including the 2.2 million sq ft of sheet needed for the column covers, and is fabricating the special castings that hold the panels in place. The panels, however, are being fabricated in St. Louis, Mo., by the Cupples Products Division of the H.H. Robinson Co. Collyer Associates, Inc., New York City, erects the panels. An affiliate, Collyer-Sparks, also of New York City, installs the glass. Mario & Di Bono Plastering Co., Great Neck, N.Y., handles the fire-proofing.
A major problem facing the contractors at the outset of the job was development of a safe and fast way to attach the column covers to the structural steel. Cupples solved this by designing a three-piece, die-cast mounting assembly. Two of the pieces are left and right aligning pins that are welded to the top of each column cover during fabrication. The third unit is a column cover anchor that bolts to the outside of the structural steel spandrel just above floor level to hold the covers.
The anchor casting is easy to set. One man does it in a matter of minutes while working from inside the building. He simply puts his arm out the window with the casting in his hand and brings the casting back against the spandrel so that its four integral bolts come through pre-drilled holes in the steel. By hand-tightening nuts on the bolts he completes the initial anchor installation.
Subsequently another man, also working alone, aligns the casting with the help of a jig containing two levels (see picture, bottom p. 36) and tightens the bolts with a spud wrench.
Automated drilling. Drilling holes for the cover anchors could have been a problem. There are more than 180,000 of them; every one of them has to be in exactly the right place when it is bored through the 1 3/8-inch thick high-tensile steel. Collyer explained the problem to Ingersoll-Rand and Ingersoll designed and built a complicated but highly effective air-operated gang drill that accurately bores 12 holes 9/16 inch in diameter through the 1 3/8-inch thick steel in 45 to 50 seconds. The machine is on casters and pushed into location by two-man crews. An aligning pin on the left side of the rig fits into a previously bored bolt hole to provide perfect horizontal positioning of each set of holes.
Vertical alignment is achieved by means of fixed gages on either side. Elevation of the drill is controlled by a hand wheel at either side, and is determined by aligning a fixed gage with a pre-established mark on the steel to be drilled. Once positioned, the machine is clamped to a spandrel so it cannot move. One set-up, including the drilling, takes about seven minutes.
At the start of the job, Collyer's engineers attached a small piece of photo-sensitive tape to each column at about the proper elevation for the machine's gage. They then used a laser beam to transfer to the tape elevations provided at each corner of the floor by the port authority. Everyone concerned with the establishment of elevations agrees that the laser did an excellent job. Unfortunately, two major factors interfered with its continued use: it was too sensitive and could not be used when any machines were working on or within the building, so it could be used only at night. Later, the contractor had some trouble with the leveling table, which, when in perfect operating condition, was overly sensitive to vibrations and movements of the structure. So, from the 30th floor up, Collyer has been using a conventional surveyor's level to swing grades.
Unique attachment. One of the most interesting machines on the job is a conventional fork-lift truck that has been modified to set the outside cover panels from inside the building. The forks have been replaced by a horizontal boom that is hydraulically operated and moves up and down the fork track. The boom carries at its outer end a clamp that has a wrist action.
Workmen place one edge of a panel into the clamp at about the midpoint. At this stage the panel is horizontal and on edge (see pictures, left). The operator pushes a button to lock the clamp in place. To release the clamp, however, he must push two controls. Thus, even if the operator accidentally hits one of the release controls, he cannot drop the panel. The operator then moves the machine forward, pushing the panel endways out through a window opening. Then, with the panel still horizontal, he turns the clamp 90 deg to bring the panel parallel to the building wall. He next rotates the head to swing the panel into a vertical position. Backing of the machine brings the panel back into position against the structural steel. Two workmen stick their arms out through the opening on either side to slide the upper end of the panels inside the column cover anchor above and with the help of a man on the floor below to slide the cover into aligning pins welded to the top of the cover below.
The cover setting machine, in spite of its efficiency, is used not as a time saver but as a safety device. In good weather, Collyer's men can set the panels faster by hand, and just as safely. They attach dogged ropes to the panels by means of special safety clamps, and, working from window openings adjacent to the steel to be covered but one floor above, they lower each panel into place manually. However, in windy weather, when a panel might be hard to control with ropes, the machine with its positive grip is used to a good advantage.
Each panel is ultimately fixed with eight ¼-inch diameter bolts. The anchor castings are so effective that at the time of installation only two bolts are needed to secure the panel. The others are put in later by a crew that properly aligns each panel. While the structural steel has tolerances of 1.5 inches, the wall panels must not deviate more than ¼ inch from vertical within 12 ft and corrections must be made through three floors so that variations cannot be seen.
Complex procedure. Before the panels can be installed, however, there are several other operations to be completed, not the least of which is the installation of steel liner adapters and the application of fireproofing. The liner adapters are welded, with the aid of jigs, to the structural steel columns. They form a rough window opening and they also serve as guides for the fireproofing, which must be applied with unusual precision.
If the fireproofing extends outward too far it will interfere with the placement of the column covers. If it is too thin it will not be in contact with cover baffles and will at least partially negate the effectiveness of the pressure equalization system. It will also fail in one of its primary functions, that of providing a thermal factor needed to control column temperature. By design, the temperature of the structural steel columns is limited to a minimum of 50 F with an interior temperature averaging 70 F and an outside temperature of 0 F.
So the fireproofing is important. It has also been troublesome. Some of the material applied last winter froze and spalled off with the first thaw. This called for the removal of several floors of column covers and the reapplication of the fireproofing. The time lost from this was not as great as it might have been, however, because it came at a time when New York City banned use of fireproofing containing asbestos and forced contractors and suppliers to find other materials (ENR 5/7 p. 21).
Currently, Mario & Di Bono uses a material that is asbestos free. One contractor representative says the time lost in the changeover was so great that the summer schedule for completing wall covering had to be increased to four floors a week from the planned one- and-a-half floors per week.
With the present schedule the contractors plan to have 85 floors of cove set before the dead of winter. Then, be cause of the weather the contractors will continue to work, but at a slower pace and with a reduced number of men.
Regardless of progress after winter sets in it is certain now that by the end of the year the north tower will have tenants in all the space between the ninth and the 16th floors and the first building of the World Trade Center will be in business.
November 5, 1970
Fig . Skin on north tower is up 68 floors.
Fig . Man sets anchor casting from within the building.
Fig . Jig guarantees precise casting alignment.
Fig . Modified fork-lift, running on floor, grabs a 100-lb. 12-ft-long aluminum wall panel as a prelude to positioning it outside the building from within.
Fig . Jigs simplify setting of window jamb liners.
Fig . Tined panels cover steel to sixth floor.
Fig . Plan view of complete wall column.
Fig . Panel comes endways through window. Arm turns panel so that it parallels building wall.
Fig . Panel, now vertical, will be pulled back to wall.
AUTOMATED TRADE CENTER
New York City's $600-million World Trade Center, with its twin office towers rising 1,350 ft above a 5-acre plaza, will be equipped with a $7-million computer controlled environment. The automated system to be installed by Honeywell, Inc., of Minneapolis, will save the owner, Port of New York Authority, at least $400,000 a year in operating costs.
May 15, 1969
BLACK CONTRACTOR WINS $1.1-MILLION CONTRACT
Minority contractor Electrotorque Associates, Inc., of Brooklyn, N. Y., has won a $1.1-million electrical contract from the Port of New York Authority. The contract involves the installation of the refrigeration plant for the World Trade Center, which is presently under construction.
The contract, the largest yet performed by Electrotorque, is part of an overall effort by the port authority to involve minority contractors in its projects. In this case, the authority contacted five minority contractors who were qualified to perform the work. Two submitted bids and Electrotorque was low bidder.
The largest contract Electrotorque had previous to this was in the amount of $400,000 for electrical installation in the Bayonne (N. J.) Naval Supply Depot.
Electrotorque is also the subcontractor on the electrical work for the Trade Center's pump station, which will supply the refrigeration plant with water from the Hudson River.
July 17, 1969
Theodore W. Kheel, a non-staff adviser to New York City's Mayor John V. Lindsay, is studying a possible court action to force the sale of the Port of New York Authority's twin-tower World Trade Center. Kheel claims the bi-state authority neglects transportation in the region in favor of real estate development.
November 27, 1969
PORT AGENCY MAY BUY RAIL LINE, BUILD TRADE CENTER
The Port of New York Authority plans a $470-million program for the purchase, rehabilitation and extension of the Hudson and Manhattan Rail-road, and for construction of the World Trade Center in lower Manhattan.
In an agreement with New Jersey, the bi-state agency will take over the bankrupt Hudson Tubes and link them to additional New Jersey commuter railroads. The tubes, which connect downtown New York with Newark, N.J., already link with the Pennsylvania Railroad.
The agreement also calls for construction of a new Manhattan terminal for the tubes, in conjunction with the proposed World Trade Center. The present terminal, which will be demolished, is on the center's site.
The nine-block center will have a 72-story structure with world trade, government and business offices on the lower floors, and a 50-room hotel and the World Trade Institute on the upper floors. The center will also include a 30-story U. S. Customs Service Building and a 23-story structure with international shipping, banking and law offices (ENR Mar. 16, 1961, p. 25).
The Hudson Tube project will feature an extension of the line from Iloboken to Secaucus, and the construction of a $2 5-million tube and bus terminal in Jersey City. Three new transfer stations will be added to the line.
At the proposed Harrison transfer, three branches of the Erie-Lackawanna will connect with the tubes and the Pennsylvania Railroad. (The tubes lead to lower Manhattan and the Pennsylvania RR to mid-Manhattan.)
The Secaucus transfer will link the Boonton and Bergen County lines of the Erie and Lackawanna to the new extension of the tubes, and to the main line, of the Pennsylvania. The Bergen Junction transfer will also connect the Erie-Lackawanna to the tube extension.
Other tube projects include buying 250 new air-conditioned cars and replacing signal systems in the tubes. With the improvements, the PNYA estimates an increase from 60,000 to 135,000 regular commuters.
The Authority will spend $200 million on the tube project. Originally, an $83.5-million investment was scheduled. Previous plans also called for a $355- million World Trade Center. With the recent revision, the center will cost $270 million. The PNYA estimates a loss of $8 million a year on their first rapid transit venture
A speedy passage of enabling legislation is anticipated in both states.
February 1, 1962
JUICY DESIGN PLUM
The Port of New York Authority named Minoru Yamasaki & Associates of Birmingham, Mich., as architects and Emery Roth & Sons of New York City as associate architects of the $270-million World Trade Center. Providing facilities for the export-import business, it will occupy a 1 5-acre site along the Hudson River, near Wall St.
September 27, 1962
COURT UPHOLDS TRADE CENTER JOB
New York State's highest tribunal, the Court of Appeals, reversed a lower court finding that condemnation of land for the proposed $270-million World Trade Center in New York City is unconstitutional (ENR Feb. 28, p. 49).
Identical legislation passed last fall in New York and New Jersey directed the Port of New York Authority to take over a 16-acre site on the Hudson River in lower Manhattan and erect the Trade Center.
The statutes also directed the bi-state agency to acquire the bankrupt Hudson & Manhattan Railroad and operate its commuter lines connecting New York City with three New Jersey cities, Hoboken, Jersey City and Newark. The decision of the Appellate Division of the State Supreme Court six weeks ago halted $150 million worth of construction and modernization on the H&M tubes.
Finding in favor of a group of businessmen who would be displaced by the Trade Center, the lower court held that the New York statute is unconstitutional since it does not specify how much of the land condemned should be devoted to public purposes. The statute permits use by private tenants, but does not limit extent of such use, the court said.
In reversing this decision, the high court noted that the statute allows only parts of the public buildings to be used for incidental revenue to cover all or part of expenses of the project. Thus, the majority held, the legislation does not allow unfettered construction of structures that would be solely revenue-producing.
The plaintiffs will appeal to the U. S. Supreme Court. Confident that the Supreme Court will not even hear the case, however, Port Authority officials are moving to advance architectural work on the Trade Center and revive plans for the transit line.
April 11, 1963
WORLD TRADE CENTER GETS GO-AHEAD; WORK STARTS
The U. S. Supreme Court last week refused to bear an appeal aimed at barring a start on New York City's $270-million World Trade Center. The Port of New York Authority immediately announced that it would order the architects to start work on functional planning and architectural design. Activity halted February 20 when businessmen in the 16-acre area to be condemned brought suit on grounds that the legislation authorizing the project violates constitutional limits on the right of eminent domain (ENR April 11, p. 77).
November 21, 1963
CONSTRUCTION'S MAN OF THE YEAR: WORLD TRADE CENTER'S RAY MONTI
The Port of New York Authority's $650-million World Trade Center is a six-building complex that includes the world's two tallest buildings. At any-time, an average of 3,500 men are at work for the project's 200 prime contractors and 500 subcontractors and suppliers. The two 110-story, 1,350-ft high office towers alone will include 192,000 tons of structural steel, 208 elevators, 3,000 miles of electrical wiring 43,600 windows, 7,000 plumbing fixtures, 40,000 doorknobs. The site is hemmed in by Manhattan's bustling financial district on three sides and the Hudson River on the fourth.
The World Trade Center (WTC) is remarkable not only for its architectural and engineering advances, but for the program of construction management that brings together the right men, materials and tools at the right place for the right work at the right time over a seven-year program.
The man who established this plan and is carrying it through is 41 year old Ray M. Monti, construction manager on the WTC for the Port of New York Authority (PONYA). Monti, a civil engineer with PONYA since 1952, was brought into the WTC project in 1964, when Minoru Yamasaki and Associates, Birmingham, Mich., and Emery Roth and Sons, New York City, were still preparing architectural plans. Actual construction began in 1966.
Monti spent a year and a half organizing a 128-man construction team and preparing a critical path method (CPM) construction plan that not only schedules the thousands of elements of WTC construction, but rides herd on construction materials and up to $10 million monthly in contractor payments. The CPM program for the World Trade Center is operated from a PONYA computer because it is too vast to be committed to paper.
The WTC construction division is made up of supervising and senior engineers who operate as resident engineers on the major elements of the project, such as North Tower, South Tower, below grade, Customs Building, and they are backed up by staff units devoted to contract management, logistics and offsite inspection, and safety.
"Once the plan was developed and the top men knew what their responsibilities were, I began a management by exception operation," says Monti. "As a result, I deal entirely in crises. No good news ever crosses my desk. I don't even want to hear about things going well, except at weekly meetings."
A typical Monti day: discuss temporary shelter, additional manpower and fire protection in the towers with his second in command and the general contractor; meet with a contractor about labor problems; go below grade on the site to investigate a water problem; talk with an electrical contractor about conduits put in wrong; cope with a marble contractor who claims other trades hold up his work; meet with a plumber about test pipes that are freezing; work out a settlement for changes with a contractor; rush to the clinic-an ironworker fell two floors and hit a PONYA engineer. Although his staff screens his mail, he usually takes home 100 pieces of correspondence to work on after dinner.
Background to management. Monti is a vigorous, energetic man of slightly less than average height. He has a full head of almost black hair and strong, slightly irregular teeth. He wears fashionably cut suits and because of them is known as the Count by engineers at PONYA headquarters. Like several of the senior men on his staff and many other PONYA engineers, he was a Seabee officer.
Monti was graduated in 1952 from Manhattan College (which is actually in the Bronx), where the civil engineering department is typically design oriented.
"There were three books that were holy at Manhattan," says Monti. "They were the BIBLE, the STEEL HAND-BOOK and the LINCOLN ARC WELDING HANDBOOK. I took a design job right out of school with one of the big design-construct companies. My first week I did stair details for Midwest power-plants, risers and treads all week. The next week I was still on risers and treads. I took a look at what the man behind me was on. He seemed to be about 80 and he was doing stair details, risers and treads. I quit the next week."
Before his graduation, Monti took the Port Authority examination for junior professional trainees. "The Port Authority has an insidious way of doing things," says Monti. "First they told me I was one of 2,200 under consideration. Then they wrote to say I was one of 200, and they wanted me to take more tests. I did and I came out one of 25. By that time it became a challenge. Finally, I was one of nine accepted for the program. I started shortly after I left that design job."
Monti was supposed to begin a two- year tour in the Navy following college. PONYA got the Navy to postpone this and Monti spent a year serving in each of the major PONYA departments.
When he reported for duty as a Navy Civil Engineer Corps ensign in 1953, he found to his surprise that he'd leave within three days for Port Lyautey in what was then French Morocco. It was also a surprise to the commanding officer at Port Lyautey, who was expecting a lieutenant commander to run construction of 800-ft-high radio antennas.
Despite his low rank, he got the responsibility. He liked the Navy so much that he planned to stay in. But the late John Kyle, who was PONYA chief engineer, used to write to Monti every three months, describing the projects the Port Authority was working on. Monti decided to give PONYA and civilian life a two-year trial. The Port Authority won.
On to fortune. In JULIUS CAESAR, Shakespeare wrote: "There is a tide in the affairs of men which, taken at the flood, leads on to fortune." Monti began riding that tide at PONYA like a championship surfer and he's been hanging 10 ever since.
After the Navy he worked in the engineering department's construction division on Kennedy and Newark airports and the third tube of the Lincoln Tunnel. He next served two years in the department's structural integrity team, a five-man group that double-checked on the soundness of PONYA construction work. By 1959, he'd been promoted through the ranks of Engineer I, II, III, and IV. Late in 1959 he got the first of his big jobs, promotion to assistant resident engineer on the $30-mil- lion expansion of PONYA's mid-Manhattan bus terminal.
The terminal, which stands near the Manhattan end of the Lincoln Tunnel, was built in 1950 and had outgrown its capacity. The only way to go was up, so PONYA designed three additional floors supported on giant prestressed steel girders resting on concrete-encased steel columns straddling the terminal.
The main challenge of the job was the foundation work for the columns, which go down to bedrock in narrow excavations, and this was Monti's responsibility.
The resident engineer on the terminal job was Frank Corey, "a real old-line construction man, a tobacco-chewing type," says Monti. "I learned a lot from him and through him. After the foundation phase was done, Corey called me into his office and said I was relieved of all other duties and from that time on I'd handle only the electrical and mechanical work. I pouted a bit; thought he didn't like my work on the structure part of the job. But that was the best lesson I ever had. That background in electrical-mechanical has been invaluable to."
Toward the end of the bus terminal project, Monti and another engineer on the job were assigned to a three-day course at Saranac Lake, N.Y., in CPM. "Sometimes things happen in strange ways," says Monti. "We considered it a junket. At that time CPM was just breaking out. We came back and kind of forgot about it."
Critical path to promotion. Because of Monti's performance on the bus terminal job, he was promoted to resident engineer in charge of the $5-million Port Authority Heliport and Exhibit Building at the New York World's Fair. Louis Booth, then manager of PONYA's construction division, suggested that Monti try out CPM on the heliport.
The PONYA fair building looks like a 120-ft-high card table with the legs at the mid-points of the sides, instead of at the corners. The steelframed building (still standing) has a heliport deck and two floors of restaurant on top of its tower legs.
Foundation work began Aug. 1, 1962, and the official opening was set for Oct. 1,1963. By the time the foundation work was two weeks under way, Monti's CPM network told him that it would be completed two weeks behind schedule. The foundation contractor agreed to speed up the program in the final month if the work conflict that Monti predicted actually materialized. The conflict did arise and the contractor crashed the job with men and overtime, meeting the schedule.
Using his CPM network again, Monti convinced the steel erector to work several Saturdays and other overtime, and the steel was topped out on schedule. The superstructure contractor, W.J. Barney Co., New York City, had never used CPM before, but was willing to try it. The CPM network kept Barney, and Westinghouse, the elevator contractor, working Saturdays. Work went on schedule until Sept. 7, a Saturday.
During the night, a broken water main dumped 1.5 million gal of water into the basement, putting the electrical-mechanical equipment under 7 ft of water. Monti rounded up the PONYA pumping equipment from the George Washington Bridge, the Holland Tunnel and Kennedy and La Guardia airports. Barney men borrowed machines from other contractors at the fair. By 7 p.m., the basement was dry. The job went into a 100% crash program. Within two weeks, all the machinery was either repaired or replaced. By 5:30 p.m., Oct. 15, the tenant's contractor was applying the last paint to the lobby ceiling. By 6:30 the first guests arrived for the building's dedication.
On-schedule completion of the PONYA fair building confirmed Monti's status as one of the authority's bright young men (he was 33 then) and won him the PONYA Executive Director's Award of Achievement. It also made him Mr. CPM at the Port Authority.
Meanwhile, back at WTC. Monti's performance on the Port Authority's fair building won him his assignment to the World Trade Center in 1964. By the time he arrived, the architects had gone well beyond the conceptual stage and the job was taking shape. To be resolved was not only how to build it-Monti's assignment-but who to build it.
The Port of New York Authority during the past 50 years has built some $2 billion worth of bridges, tunnels, airports, piers and buildings within a 25-mile radius of the Statue of Liberty, but no high-rise buildings.
Guy F. Tozzoli, director of PONYA's World Trade Department, concluded early that the World Trade Center was too big for any contractor to build. "I asked myself," he says, "Why should I not assume the functions of a general contractor if I have the advice of experts in the field?"
In April, 1964, Tozzoli and Malcolm Levy, chief of WTC planning and construction, engaged experts, four New York City contractors prominent in high-rise work to review the construction techniques it planned to use on the two towers. They were Diesel Construction Co., Turner Construction, George A. Fuller Co., and Tishman Realty and Construction Co.
Early in 1967, PONYA retained Tishman to act as general contractor agent for the World Trade Center, at a fixed fee of $3,250,000 plus reimbursement for field costs. Tishman assumed responsibility for coordination of trades, supervision of construction, and movement of men, materials and machinery on the site. And the Port Authority, acting pretty much as its own general contractor, let 200 prime contracts for WTC. In addition to his organizing and construction planning duties, Monti took part in an elaborate program of contract letting.
For each of the 200 prime contracts, prospective bidders were called in individually to discuss the total project and the work they might do in it. Interested contractors were asked to submit a proposal as outlined in bid documents and also-since they were the experts-any alternate proposals for more efficient or less expensive construction. Contractors that came up with the best plans and prices got the jobs. Some benefits of this time-consuming process were:
Dry run construction. The first man that Monti recruited for his staff was Charles Smith, a former Seabee officer and an expert in CPM. Next came Francis H. Werneke, also an ex-Seabee, and now Monti's second in command.
- The elimination of some expensive caissons in the foundation of the South-east Building.
- A cost reduction in extension of temporary power throughout the buildings.
- Improved distribution systems for HVAC.
- Improved slab support for the foundation walls.
As each contract was let, Monti and Smith got a CPM plan from the contractor, a sequence in regard to time and cost. For contractors with no CPM background, the World Trade Department ran a free course of instruction.
All the CPMs submitted by contractors were integrated into an overall network that contains every item of work in the most efficient sequence.
The result is a master construction plan that is resilient enough to adjust to changes, redesign, strikes, bad weather, accidents, labor shortages, late deliveries and transportation failures without losing time. When something goes wrong, Monti's staff can work around it to avoid losing time.
Once the bones of construction planning were established, Monti and Smith did a dry run on the computer on construction of the North Tower.
"We came up with 24 months per tower, with a seven-month lag for the second tower," says Monti. "It took 28 months for the North Tower, which topped out late in December. We expect to top out the South Tower in June. We're behind schedule. The strike of elevator constructors in 1969 lasted almost exactly four months. We were able to keep a lot of contractors going, but we lost production."
The logistics of steel. Only two companies bid to supply steel for the WTC. PONYA decided those bids were way beyond its budget and rejected them. Next, it broke down the steel fabrication into small segments and invited bids again. The total value of steel contracts fitted with the WTC budget, but the builders of WTC ended up with 15 fabricators spread across the country.
Despite the breakdown of the steel contract, the orders were still so big that WTC had to give them an OK to start 18 months before their steel was needed. As further complication, there's no place to store steel on the cramped WTC site. In fact, unloading space is so limited that a piece of steel has to arrive only minutes before a crane is ready to pick it up.
Monti, with William Borland, a former Army engineer, developed a program that keeps tabs on steel from its raw state through to installation. A data processing system permits them to monitor the fabrication of steel, know when it has been accepted by a WTC inspector at the plant, know when it was shipped, when it arrived at a New Jersey storage yard and is to be shipped to the job site within minutes of when it will be needed for erection.
This computer-operated program enables the arrival, hoisting and installation of an average of 600 tons of steel a day by Karl Koch Erecting Co., New York City. Under this system, WTC can anticipate trouble, can know if a piece of steel is missing long before it should be under the hook.
Although the emphasis is now on steel, it will move soon to electrical-mechanical equipment, later to furniture and draperies.
Monti on management. Monti operates from the 10th floor of a building overlooking the WTC site. Although he concentrates most of his attention in areas where things go wrong, he maintains constant communication with the main contractors, with the architects and with the engineering consultants, Skilling, Helle, Christiansen, Robertson, Seattle, on structural design; Joseph Loring & Associates, New York City, on electrical work, and Jaros, Baum & Bolles, New York City, on mechanical.
"I see my role as primarily one of motivating people to get the job done," says Monti. "The motivation I use is whatever motivation will work best, friendliness, saying please, telling jokes, shouting and yelling where it's needed, threatening where it's needed. I've got to see that things get done, not only on a day-to-day basis, but to anticipate the needs of six months from now."
Construction management or administration often gets him a long way from the things he learned in engineering school, but Monti thinks it's the way it should be.
"When I was an engineering student I thought that engineers did two things: they designed welded steel bridges and they poured concrete," says Monti. "Since then I've found that as an engineer's job gets bigger and more complex, the percentage of time he devotes to administration increases."
"I'm involved in purchasing, labor relations, site security and public relations. I'm a part-time lawyer, accountant, salesman, architect and personnel man. Although it's all administration, without my engineering and construction background I couldn't have made these administrative decisions."
February 11, 1971
Fig . Ray Monti's day
Fig . Car radio gives him an early start on the day's problems.
Fig . Steel delivery paces progress.
Fig . Conferences with senior staff occur throughout the day.
Fig . World Trade Center will top out second record-high tower in June.
Fig . Bearing wall steel demands close tolerance.
Fig . Steel inspector brings him up to date.
Fig . Some days, nothing seems to go right.Monti reports on progress to Guy F. Tozzoli (center), World Trade Department director, and Malcolm Levy (left), chief of planning and construction division.
Fig . World's Fair heliport construction won a PONYA medal for Monti.
BUSINESS AND FINANCE
COURT ACTION HALTS MAJOR PROJECTS
Decision jeopardizes New York City's proposed World Trade Center and a two-state rail network.
Court says a public agency can't take land for a project for benefit of private enterprise primarily.
A state court decision last week clouded the future of New York City's proposed $270-million World Trade Center. It also suspended $1 50 million worth of planned modernization for the Hudson tubes, a 7.9-mile transit line that connects the city with three New Jersey cities, Hoboken, Jersey City and Newark.
The Appellate Division of the State Supreme Court declared unconstitutional identical New York and New Jersey legislation passed last fall directing the Port of New York Authority to do the following:
The Port Authority immediately appealed the decision to the Court of Appeals, New York's highest tribunal. Austin J. Tobin, executive director of the bi-state agency, expects fast action on the appeal because of the public interest involved.
- Take over and operate the bankrupt Hudson & Manhattan Railroad and its 22-story terminal buildings in Manhattan.
- Condemn a 16-acre site for the Trade Center to be located along the Hudson River in lower Manhattan (ENR Sept. 6, 1962. p. 21).
Confident of a reversal in the highest state court, he also forecasts that the U. S. Supreme Court will then refuse an expected request for review from opponents of the Trade Center. Settlement could be achieved within weeks, says Mr. Tobin.
Upholding the argument of a group objecting to the Trade Center, the Downtown West Small Business Survival Committee, a 3-2 majority held that the two-pronged statute violates constitutional limits on the right of eminent domain, stating:
According to Authority plans, a 72-story structure would dominate the Trade Center. It would contain business and government offices, a hotel and World Trade Institute. Other major components in the area would be a 30-story U. S. Customs Service Building and a 23-story structure for law, banking and international shipping offices (ENR Feb. 1, 1962, p. 21).
- "While it might not do so, what is to prevent it (the Port Authority), if it so chooses, and acting within the power conferred by this statute, from using nine-tenths of the 13 blocks for revenue-producing purposes and but one-tenth for public purposes?"
- "The legislature authorized the Authority to construct such buildings as customs houses, customs stores, foreign trade zones and like facilities-all clearly for public purposes-but failed to limit such authorization to that type of building. On the contrary, it expressly permitted the Port Authority to erect buildings and use warehouses for functions 'incidental to . . . the exchange, buying, selling.., of commodities and other property in world trade and commerce .'"
- "Exercising this power would indeed make this project, in reality, what the appellants call a real estate development."
- "We do not say that the state, or the Port Authority through delegated powers, may not take private property to be developed by private interests if the underlying object is for a public purpose."
- "However, to permit private interests to use condemned land for private purposes solely to produce revenue for the maintenance of a public project is . . . expressly prohibited."
Architects Minoru Yamasaki & Associates of Birmingham, Mich., and Emery Roth & Sons of New York City are already at work on the design. Construction will take about six years, once started.
Since the Trade Center will just about pay its way and it would be difficult for private interests to assemble the land, legislators chose the Port Authority to undertake the development.
It was packaged with the rapid transit project to make both acceptable to the two states since the legislatures could not agree on either project alone. Therefore, it is doubtful that new statutes will be sought to support acquisition of the railroad if the merchants' suit is ultimately successful. Other legislative remedies, however, may be available to save the entire package.
Meanwhile the Authority continues to operate the Hudson tubes under its Port Authority Trans-Hudson Corp. (PATH), although it must turn the property back to the H & M Corp. in the event higher courts uphold the decision.
When the Port Authority acquired the bankrupt railroad, the number of money-losing transportation projects rose to 15, out of 23 it operates. To underwrite its first rapid transit operation in the first year, the Authority budgeted $4.5 million. Still the Authority planned to spend $150 million on the line for rehabilitation, new construction and new equipment.
Part of this would go for a new downtown Manhattan terminal since the present one stands on the site of the proposed Trade Center. A second terminal in midtown, near Pennsylvania Station, would remain.
New construction would also extend the tubes about four miles from Hoboken, one of the New Jersey terminals, to Secaucus, replace the Jersey City station with a combination bus-rail station, and add three new transfer stations. These projects would tie all Erie-Lackawanna Railroad commuter lines to the tubes and the Pennsylvania Railroad at Newark.
Associated with this is a State of New Jersey project, already under way, to connect the Jersey Central and Lehigh Valley Railroads with the Newark facilities. This plan depends upon increased Hudson tube capacity.
Together, these projects would give all New Jersey train commuters direct railroad access to New York City. Many now must use both rail and ferry transportation.
Toward this end, the Port Authority was to open design proposals last week for 250 new cars but put off action pending outcome of the appeal.
Mr. Tobin pointed out that the court contest affects over 100,000 commuters. He also said the Port of New York has been losing tonnage and the proposed Trade Center is the only way to win it back by making the area more attractive to shippers.
Philadelphia, New Orleans, Houston and San Francisco all have similar foreign trade complexes built and operated by public agencies.
February 28, 1963
A LOOK AT THE NEW RECORD
The construction industry was startled by the Port of New York Authority announcement last week that its proposed World Trade Center will include the world's tallest buildings. The belief was widespread that such high structures are uneconomic. And well they might be if certain special conditions did not prevail.
The Trade Center will have twin 110-story towers, rising 1,350 ft above the streets, 100 ft higher than the Empire State Building without its antennas (ENR Jan. 23, p. 33). The project will occupy a 16-acre site in downtown Manhattan and will include low buildings, a 5-acre plaza, a terminal for an interstate railroad and facilities for U. S. Customs.
A major factor contributing to the feasibility of this $350-million project is the unusual owner. The 43-year-old PNYA, as an agency of the states of New York and New Jersey, can exert the power of condemnation to assemble the plots needed for the site. Also, while the Trade Center is expected to be self-supporting, the Authority's credit is backed by tolls from its bridges and tunnels. And PNYA holdings are tax exempt, though it usually makes payments in lieu of taxes to local jurisdictions. Thus, the PNYA has prestige, power, resources and privileges that ordinary owners lack, and these can be a powerful force in promising success for the record-breaking skyscrapers.
This unusual owner is also willing to invest more heavily, even sacrifice some financial returns, for public relations and political purposes than would an ordinary owner. Thus, the PNYA will not build as high as permitted all over its property, despite the high land costs in downtown Manhattan. Instead, the twin towers will occupy only 12% of the site. This plan should please the numerous vociferous critics of other recent New York projects not surrounded by large open spaces. It also permits the towers to be built with no setbacks without violating zoning regulations. Over-all, the design not only appears to be esthetically preferable to a set-back silhouette, but also lends itself to more economical construction and use of space.
The PNYA, in addition, has engaged noted architects and consulting engineers to design the project. From the preliminary data released, it appears that the design of the twin towers will mark an important advance in skyscraper construction. Tall buildings are handicapped economically because the cost of structural framing and the space consumed by vertical transportation rise rapidly with increasing height. The Trade Center designers have departed from usually conventional practices to cut these costs.
To keep structural costs down, the tower design makes the exterior walls loadbearing; they will carry the floors and resist wind loads. To conserve floor area, a novel elevator system, which treats each tower as if it were three separate buildings one atop the other, will be assigned at most one-fourth the area of each floor, whereas in many skyscrapers the space requirements for elevators add up to more than half a floor.
Construction of the record-breaking skyscrapers will be a prodigious undertaking. Each will require about 86,000 tons of structural steel, the whole project about 200,000 tons. (The Empire State Building took 60,000 tons, the huge Pan Am Building, 45,000 tons.) Elevators will be the world's fastest, at 1700 ft per minute, and have by far the largest high-speed cabs ever installed. The project's air-conditioning system will require 40,000 tons of refrigeration and 80,000 gal per mm of river water. Electrical needs are estimated to total 60,000 kw, equivalent to that of a city with 400,000 population, such as Syracuse, N. Y. Pressure in water pipes may exceed 500 psi. And these are only a few of the enormous requirements of this colossal project.
If the Empire State Building's 33-year-old height record is to be exceeded, it will pass to a worthy successor in this huge World Trade Center.
January 30, 1964
NEW YORK'S 110-STORY TOWERS
Most local designers and builders want to know more about the New York World Trade Center and its sky-shattering heights (ENR Jan. 23, p. 33), but they generally like what they've seen so far.
Carl Morse, president of Diesel Const. Co.
"It's quite an exciting project. It may be the best thing for the area, or the worst. It's still too early to say."
J.W. Pickworth, consulting structural engineer
"We can't see any reason why a building of that height shouldn't be built."
Office of Building Commissioner Birns
"It definitely will add something to the city, but provisions will have to be made to make the project fit into the city with traffic, codes and zoning."
Jeffrey Lawford, president of New York Chapter of American Institute of Architects
"We dont know enough about the project yet, but from the pictures we've seen, it all looks fine and very handsome. We're all anxious to see the details of the plans."
James Ruderman, consulting structural engineer
"The structural design of the tower buildings shows a commendable job of rethinking, where ideas were given a lot of thought and not just treated routinely."
William Zeckendorf, president of Webb & Knapp Inc.
"I'm very enthusiastic about the project and think it will be a beneficial addition to the city. It's height is really an architectural triumph."
Harold Bernhard, partner, Shreve, Lamb and Harmon Associates, architects
"It's a magnificent project."
Charles Stanton, head of Charles Luckman Assoc., N. Y. office
"As architects, we're eager to study the details and discuss it from a professional point of view. It really was a great opportunity for Yamasaki and the Roths to work with so much acreage in a big city."
January 30, 1964
NEW FACE FOR LOWER NEW YORK
New York's lower Manhattan, which takes in the Wall Street financial district, is candidate for an estimated $1 billion redevelopment and rehabilitation program. The plan was drawn up by the Downtown-Lower Manhattan Association; it was given to Mayor Robert F. Wagner last week. New York City's Board of Estimate will consider it this week.
No time estimate is placed on the program.
The proposals, including public and private work, would bring sharp changes within the 564-acre area encompassing the financial center of the world.
The following improvements are projected:
Two areas - The plan calls for two redevelopment areas; one on the east side and the other on the west side of the island's lower portion.
- Razing most of the outmoded structures to permit expansion of the financial district and other forms of redevelopment.
- Closing many of the narrow streets by assembling the land for housing and industrial use.
- Widening other streets to create an interior traffic loop.
- Replacing some piers along the East River with a heliport and small boat marina.
The west side section would extend south from Canal to Cortland Streets, a distance of about 20 blocks and ranging in depth from one to four blocks. The east side section would extend south from Brooklyn Bridge and end at about Battery Park. This too would include about 20 blocks, with a depth of from five to two blocks, exclusive of pier area also to be redeveloped.
Three basic elements - The plan, based on studies made by Skidmore, Owings & Merrill, New York City architects-engineers, is designed to accomplish three things: improve traffic flow; organize economical land use; and designate specific areas for redevelopment. These are "basic to further progress," the report states.
The report also explains that "pending discussion, cost studies and positive action by the city, we have deliberately omitted . . . the form of future redevelopment, the means for its realization and costs involved."
The $1 billion cost estimate is unofficial.
The area would be re-zoned into four classifications: general commercial, heavy commercial, light industrial and residential.
Each of these zones would be a sharply defined and unified area, although the report emphasizes that the suggestions are only a "broad outline subject to further review and modification in the light of future developments."
David Rockefeller, vice chairman of Chase Manhattan Bank. is chairman of the association and John D. Butt, chairman and president of Seamen's National Bank, is association president.
October 23, 1958
IN NEW YORK, A WORLD TRADE CENTER
A proposal to build a World Trade Center in the financial district of downtown Manhattan generated widespread enthusiasm among New York business executives and government officials last week. Estimated to cost $250 million, the center would be the first stage of a $ 1-billion redevelopment program for lower Manhattan proposed over a year ago (ENR Oct. 23, 1958, p. 77).
The plan calls for clearing a 1 3!acre site on the East River. Only two existing buildings would remain. An elevated plaza, two stories above grade, would cover the entire site. Three buildings would rise out of the plaza nine-story World Trade Mart, 880 x 365 ft in plan, with two interior courtyards; a 50to 70-story commerce office hotel building; and a Central Securities Exchange Building.
The giant World Trade Mart would provide office and display space for international trade activities, offices for insurance brokers and travel offices. It would contain exhibit space for governmental trade missions, space for commodity exchanges and an international clearing house for merchants.
The commerce building would house U. S. and foreign business, banking and brokerage firms in international markets. A world trade club would provide meeting rooms for foreign and American citizens engaged in this field. Ten floors at the top of the building would furnish 500 to 700 hotel rooms to accommodate transient shippers and international merchants.
Planners hope to have the New York Stock Exchange as .a tenant in the Central Securities Exchange Building to be a world trading center. Stock Exchange officials have made no commitment yet.
Shopping arcades occupy the main concourse at street level and the floor above. One underground level contains parking, loading and storage areas.
A proposed heliport, adjoining the site on the East River, would provide rapid access to metropolitan airports.
The Lower Downtown Manhattan Association, a civic organization representing business firms and real estate owners in downtown New York, sponsors the redevelopment studies. The association's report recommends that the Port of New York Authority make detailed studies on planning, financing and putting the center into operation. This recommendation was sent to Governor Rockefeller of New York, Governor Meyner of New Jersey and Mayor Waaner of New York City.
Association Chairman David Rockefeller said he expected most, if not all, development money to represent private investment. There is no target date for construction. But Mr. Rockefeller expressed hopes that the Trade Center could start taking leases when foreign visitors arrive for the New York World's Fair in 1964.
Skidmore, Owings, and Merrill, New York City architects, are planning consultants for the Lower Downtown Manhattan Association.
February 4, 1960
THE HIGHEST TOP OUT AGAIN
New York City's World Trade Center will be the site of a topping out and a pair of presentations this week. The south tower, one of the center's twin towers, is scheduled to be topped out. The north tower was topped out last December. And James C. Kellogg, III, chairman of the Port of New York Authority, owner, will accept from Oscar Bray, president-elect of the American Society of Civil Engineers. that organization s award to the center as Outstanding Civil Engineering Achievement for 1970. And Raymond Corbett, of the AFL-CIO ironworkers local, will accept an award of appreciation to the workers from Kellogg.
July 15, 1971
PACT CLEARS THE WAY FOR $525-MILLION PROJECT
A financial and city-improvement agreement reached last week between New York City and the bistate Port of New York Authority cleared the way for a quick start on the authority's $525million World Trade Center in lower Manhattan.
Before the end of this month, the authority will receive proposals on more than $100 million worth of construction work. This week it took bids for demolition work in the 16-acre tract. Next week it will receive from Bethlehem Steel Corp. and United States Steel Corp. proposals on the 185,000ton structural steel contract for the center's twin towers, each 209 ft square and 1,350 ft high. On August 26, the agency will receive proposals for the main' foundation contract, which will include excavation and construction of a perimeter wall.
The agreement permitting major proposals on the building project came after six months of bitter wrangling between top city and authority officials, and after five years of litigation initiated by private interests opposed to the project.
The dispute involved both the amount of money in lieu of taxes the city would receive from the authority, and improvements outside the trade center area, but within the city, that the authority would finance in whole or in part.
A committee negotiating for the city hoped to obtain annual payments of $18 million, and $242 million in capital investment by the agency, within the city, in addition to the trade center.
Less than sought - As finally negotiated, the authority will pay to the city about $1.7 million a year during the period of construction, which may run through 1970. In the first year of completed occupancy, the authority will make an "in lieu" payment of about $6.2 million. And over the life of the project, the annual payment will rise or fall to the extent that the tax rate and assessed valuations on comparable privately owned properties increase or decrease. Officials of both the city and the authority describe the concept of basing payments on current value of private property as a major innovation in authority-government relationships.
Negotiators for New York also obtained agreement for authority-financed improvements within the city that will cost an estimated $146 million.
Other points of the agreement include:
Waterfront renewal - Authority officials also agreed to determine quickly the economic feasibility of a consolidated passenger ship terminal on the Hudson River in Manhattan. It will send a definitive report to Mayor John V. Lindsay within four or five months.
- Expenditure of $7.5 million by the Port Authority to improve public facilities during construction of the trade center. The authority will widen streets, improve sewerage lines, install larger water mains and construct three pedestrian underpasses. In addition, the authority will pay for all on-site utilities relocation and traffic control systems.
- Widening streets surrounding the trade center, which will involve conveyance to the city of approximately 160,000 sq ft of authority property.
- Creation of 28 acres of new land for the city along_the_lower Manhattan waterfront by filling the site of some obsolete piers along the Hudson River between the southern tip of Manhattan and the trade center. Officials estimate that sale of this land to private developers will bring $30 million to the city treasury. Among proposals for this site is a middle-income housing project.
Also, the authority agreed to invest $6.6 million in a proposed waterfront renewal project in Brooklyn, another borough of New York City. This project involves about 60 acres, and plans call for a containerized cargo-handling terminal and some medium and light manufacturing plants.
August 11, 1966
CONTRACTS ON TALLEST BUILDING
The Port of New York Authority last week awarded the first major construction contracts, totaling $62.2 million, on the $525-million World Trade Center in New York City's lower Manhattan. One of them, to Otis Elevator Co., of New York, is the fattest plum ever plucked by the elevator industry: $35 million for 46 of the largest high-speed passenger elevators ever built, plus 154 other elevators and 49 escalators. A joint venture of five New York City contractors landed an $18 .7-million excavating contract. And IGANDA, Ltd., of Montreal, took an $8.4-million contract for construction of a 3,100-ft basement wall.
November 24, 1966
TRADE CENTER OPPONENTS SAY BIDS DOUBLE ESTIMATE
Opponents of the proposed $525million World Trade Center in New York City this week charged in a full-page advertisement in THE NEW YORK TIMES that the total of bids received on two major phases of the project exceeded estimates by 104%, or $91 million.
The owner of the twin-tower commercial complex, the Port of New York Authority, declined comment "on any aspects of Mr. Wien's advertisement." Lawrence A. Wien, owner of the Empire State Building, which would be topped in height by 100 ft by each of the 1,350-ft trade center towers, heads the Committee for a Reasonable World Trade Center, sponsor of the advertisement.
The advertisement says, "As against reported estimates by the professional staff of approximately $400 per ton an4 a total requirement of 180,000 tons, the rumored low bid is more than $650 per ton and a requirement of more than 220,000 tons." These figures work out to a steel cost of $72 million, as reportedly estimated by the authority, but a "rumored" bid price of $143 million.
The advertisement also says, "The staff estimate for excavation was $16 million. It is reliably reported that the first group of bids are about $36 million."
October 6, 1966
BIG STEEL CAGE GOES UNDERGROUND
Seven-story-high reinforcing cages, each weighing almost 25 tons, are being lowered into the ground at the site of the World Trade Center in lower Manhattan. The 152 cages, made of high-strength steel, will reinforce a section of the 3,300-ft cut-off wall being built by the slurry method around the center's eight-square-block area.
Solid shapes hanging diagonally from the cage (see picture above) are insert ports through which the contractor, Icanda Ltd., of Montreal, will slide anchor rods to tie the wall to rock, making internal bracing unnecessary.
Concrete wheels (arrow, picture right), using reinforcing rods as axles, roll against the sides of the trench as the cage disappears into the slurry. They prevent the bars from scraping earth from the walls of the excavation, thus jeopardizing the integrity of the concrete to come.
The World Trade Center is being built by the Port of New York Authority at a cost now estimated at $575 million. Its 1350-ft-high towers will be the world's tallest buildings.
Fig . Cage is one of 152 that will go into a cut-off wall around the World Trade Center.
Fig . Wheels (arrow) are concrete spacers.
June 1, 1967
Japan's largest steelmaker, Yawata Iron and Steel Co., recently shipped to New York City's World Trade Center part of a 3 8.600ton order of a special grade high-strength steel. Under contract between Seattle-based fabricator Pacific Car and Foundry. Yawata and Kawasaki Steel, the two Japanese firms will supply 44,100 tons (worth $8.3 million), mostly in the form of ½-in, to 3-inch thick plates.
November 9, 1967
TRADE CENTER COST: $525 MILLION
Total cost for New York City's long-planned World Trade Center (ENR Jan. 23, 1964, p. 33), which will feature twin 110-story towers destined to be the world's tallest buildings, has been estimated by the Port of New York Authority at $525 million. Unlike an earlier estimate of $350 million, this latest figure includes estimates for land acquisition, engineering, administration and financing. The original $350 million covered construction cost only.
Within the next few weeks, PNYA will initiate condemnation proceedings to acquire the 16-acre site in lower Manhattan. First-stage construction is scheduled to start before the end of the year.
Earlier this year, PNYA made a $700,000 purchase of an 18,800-sq-ft parcel, where on-site pile tests, conducted by Spencer White & Prentis, Inc., foundation contractors, of New York City, are presently under way. In 1.962, the authority acquired the Hudson Terminal Buildings on a Church St. site.
Located on the west side of Manhattan Island, near its southern tip, the 16-acre tract adjoins the West Side Highway, which overlooks the Hudson.
Proceeds from a bond sale authorized for $75 million will finance the first phase of the huge project, which is scheduled for construction in stages over the next six years.
The twin towers, designed by architect Minoru Yamasaki, of Birmingham, Mich., will rise 1,350 ft from a five-acre plaza. In these and other structures on the site, the center will bring together government agencies and private firms involved in international marketing and administrative processing of world trade. Included are the U.S. Bureau of Customs, foreign commercial attaches, foreign government purchasing missions, trade associations, exporters, importers, custom house brokers,. freight forwarders, international banks, steamship lines, and marine insurance.
Final federal approval for the plan to consolidate the offices of the Customs Bureau, now scattered in five widely separated buildings in Manhattan, came from the Public Works committees of the Senate and House this summer.
September 23. 1965
TRADE CENTER PLANS FIRM UP COST UP
Revised plans for a World Trade Center in New York City carry an estimated cost figure of $355 million. That's $105 million above the cost set just a year ago when the Downtown Lower Manhattan Association first made a formal proposal for such a center (ENR Feb. 4, 1960, p. 28).
The Port of New York Authority's revised plan-prepared for the association and submitted to the city and states of New York and New Jersey calls for an enlarged 16-acre development on Manhattan's lower east side water front. It is one of two areas named by the Downtown Association in 1958 for a $1 billion redevelopment and rehabilitation program (ENR Oct. 23, 1958, p. 77).
The revised trade center plan is dominated by a 72-story World Trade Mart (1), with a circular Stock Ex change building (2), a 20-story Gateway building (3), and 30-story Commerce Exchange (4) grouped around it. All four units would be tied together by a five-level enclosed concourse (5) extending 1,600 ft along the East River.
Altogether, the new proposal contemplates construction of 11 million sq ft of floor space. The $355-million cost is based on starting construction next year and completing the center by 1968.
Port Authority officials say the center would be "feasible" but the dollar return on it would be "marginal"; therefore only a public agency should undertake the development. And the $355-million cost assumes inclusion of some urban renewal assistance. The report maintains that the center is essential if New York City is to have a dominant position in international business and is to handle increasing amounts of cargo in foreign trade. It s on this point that the report put general need of the port ahead of "maximum economic return" from the trade center.
The revised plan includes a hotel of about 350 rooms-vs 500 to 700 rooms in the original proposal-located on the top 11 floors of the 72 story Trade Mart building. The proposed building for the New York Stock Exchange would be an eight-story, 200 ft diameter structure.
A 33-story building at 120 Wall St., that had been included in the original center plan, would be demolished. A heliport (6) on the East River and housing projects (7) would complete the area's development. (Battery Park is indicated at 8).
March 16, 1961
TIEBACK SYSTEM GIVES ELBOW ROOM
Foundation and substructure work on New York City's huge World Trade Center will be able to proceed inside a 3,400-ft-long perimeter wall unhampered by interior supports because of a prestressed tieback system.
Reinforced concrete perimeter or cutoff walls, constructed by the slurry trench method (ENR 4/13/67 p. 62), enclose the $575-million Trade Center's approximately 600 x 1,100-ft site. This permits excavation to bedrock for the foundations of the two 110-story towers and will seal off water and loose soil from future basement areas. Workers formed the walls to bedrock, an average depth of 65 ft, where pressures are expected to exceed 5,000 psi.
To counteract these tremendous pressures, the prime contractor for the $8.4million perimeter wall, ICANDA, Ltd., of Milan, Italy, constructed it 3 ft thick and is supporting It with 1,500 tieback tendons angled and anchored into bedrock 65 ft below grade. When permanent basement floors are placed to support the perimeter walls, the tiebacks will be cut.
According to E. R. Kennedy, materials engineer for the Port of New York Authority (the owner) the tiebacks consist of high-strength wires, each with an approximate diameter of 0.165 in. (270,000 psi minimum ultimate strength) and an allowable design stress of 175,000 psi.
The high unit stress required in the small wires, says Kennedy, creates a sensitivity to loss of metal through corrosion that needed to be counteracted as easy and inexpensively as possible. Groundwater at the site is brackish and only 1 ft below grade. This, plus stray electric currents flowing through the site that originate in subways and power stations in the lower Manhattan area, make corrosion a real threat.
Field tests conducted by consulting engineer, Leon P. Sudrabin, of Berkeley Heights, N. J., provided the solution: a continuous length zinc anode material attached to the tendons to provide corrosion protection along the entire length of each tieback. The anode system is a steel wire core covered with an unalloyed, low-iron zinc for cathodic protection of the tendons. According to Sudrabin, it will guard against formation of hydrogen on the steel tendons, which could contribute to hydrogen stress cracking.
Each tieback tendon consists of up to 24, ½ inch diameter high tensile strength strands, Constructed with the 0.165-in.dia wires, and ranging from 40 to 115 ft in length.
Workers welded a continuous length zinc anode to each tieback at the top and bottom to ensure good electrical contact in the event the zinc should become completely consumed at any point along a tendon.
Castings for-anchoring the tendons at as many as six different levels on each wall section were provided in the wall's preassembled reinforcing bar cage (ENR 6/1/67 p. 21), before workers began installing tiebacks.
As excavation within the perimeter wall reaches a horizontal plane of castings inclined at 45 degrees workers drill holes through the castings 30 to 35 ft into bedrock to receive the tiebacks.
Each tieback is then pushed through its rock socket, anchored with expansive grout forced through tubes running the length of the tendons, and prestressed a maximum of 600,000 lb:
May 9, 1968
Fig . Protected tieback for New York City's World Trade Center is guided to inclined casting (arrow). Casting was preset in reinforcing cage of 3-ft perimeter wall.
Early this week, almost two years to the day after start of construction, the first steel was placed for what will be the world's tallest buildings, the twin 110-story towers of the World Trade Center on Manhattan's lower west side. The steel was a 34-ton grillage, first of 28 that will support the core columns of the 1,350-ft-high north tower. Present scheduling anticipates another two years for erection of the north tower steel.
August 8, 1968