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Read part III and answer the questions after it. Make sure you can explain the following terms and word combinations from part III.
Part III. Demolition. A three-story brick building in a corner of the site was quickly demolished in two days. But when excavation of the rest of the 200 x 800-ft site began, no one knew what was below the asphalt parking lot. Excavation and foundation contractor Delma Construction, New York City, discovered that the old Garden's reinforced concrete floor slab had simply been cut in half and dumped into the building's basement. Instead of a simple excavation, Delma had to deal with a maze of underground debris. The process set the construction schedule back about a month, says Dominic Fonti, the commercial tower's project manager for HRH Construction Corp., New York City. Rebar had to be cut with torches before it could be removed by crane.
The excavation process also uncovered all of the mechanical equipment that had been housed in the basement of the old Garden. Obstacles included an oil tank full of oil that had to be emptied before it could be removed from the site, Fonti says.
To excavate the site's rocky subsurface, explosive charges had to be kept very small because blasting was so close to an active subway line. This slowed the construction schedule another three to four weeks, says Fonti. To get a close and more precise line for the charges, workers drilled holes that were about 6 in. on center. This spacing meant that the rock wall was just chipped away. When workers were as close as 20 to 25 ft to the subway, they turned to a backhoe fitted with a hydraulic hammer.
Zeckendorf had agreed to renovate and expand a subway entrance that will be part of the commercial tower. The entrance had been sealed 22 years ago when the old Garden was demolished. When workers opened it, they found lots of dust and an old token booth that was later removed—but no graffiti. It is "probably the only subway entrance [in New York City] untouched by graffiti," adds Fonti. During the excavation, the only part of the old Garden structure that was retained was its north foundation wall. Nearly 100 lin. ft o f it was integrated into the foundation wall system for the commercial tower. The superstructure of the 778-ft-high commercial tower consists of an exterior tube with a braced frame at the core. The tube resists most of the overturning moment and the braced core resists most of the shear forces.
An arcade, elliptical in plan, surrounds the lobby at grade level. The arcade's 25-ft-high granite-clad columns were prefabricated off the site. Fonti says this option was faster and saved money on labor. The 4-ft-high sections are 6 in. thick and consist of a concrete layer faced with granite. The sections are connected on the site with dowels inserted into preset holes. The 35-ft-high vaulted ceiling in the arcade is also made of prefabricated sections. Its coffered sections, with ornamental borders, are made of fiberglass-reinforced gypsum. They are hung from a metal joist framing system.
Although the arcade is open to the exterior, it is still within the footprint of the structural tube. To get the tube's loads around the three-story arcade, they are transferred to the corners of the building through heavy diagonal W14 sections.
Structural engineer Richard F. Rowe, an associate partner with SOM, explains that transferring the loads "over a couple of stories is more elegant, so the load is gradually distributed to the places that you want it." He adds that it is important to recognize that the transfers take place so you can't see them from the exterior." A network of transfers is located between the second and fourth floors. Transfers also take place in a 4 to 5-ft-high space below the second level, used as a mechanical mezzanine, says Robert P. Sanna, one of HRH's project managers on the job. Above the fifth floor, wide tube columns are used as structural members instead of W14s. Structural engineer Robert A. Halvorson, a partner with SOM, adds that the rigid frame is interrupted between the 41st and 43rd floors. The columns stay in the same location, but a 2-ft recess of the beams between the 19-ft-bays provides a setback for exterior lighting equipment to be installed. Halvorsons explains that the wind stresses are low enough at that height that the rigid frame can be interrupted without problem.
10. Answer the questions to part III:
1. Was excavation of the site simple?
2. What was below the asphalt parking lot?
3. Why was the construction schedule set back about a month?
4. Who was excavation and foundation constructor?
5. What obstacles were in the basement of the Old Garden?
6. Why were explosive charges small?
7. How were the holes for the charges drilled?
8. What was just chipped away?
9. What did the workers use when they were as close as 20 ft to the subway?
10. Why was the subway entrance different from others?
11. What part of the old Garden structure was retained?
12. What is the function of the exterior tube?
13. What is the shape of the arcade?
14. What materials are used for the arcade?
15. How are the sections connected?
16. What materials are used for the arcade’s vaulted ceiling?
17. How are the tube’s loads transferred?
18. What is Richard F. Rowe?
19. Where is the rigid frame interrupted?
20. What provides a setback for exterior lighting equipment?
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