BUILDINGS

Engineer Issues Call For Data For Building Performance Study (11/5/01)

By Nadine M. Post with Debra K. Rubin



T he new president of the structural Engineers Association of New York issued a call for volunteers to form a rotation at the two scrap yards in New Jersey receiving steel from the World Trade Center's twin 110-story towers. The call for help is part of SEAoNY's effort to assist the American Society of Civil Engineers' WTC Building Performance Study Team in its search for steel from the impact and fire floors.

"We are asking for volunteers from SEAoNY membership...to help collect data," said Edward M. DePaola, SEAoNY's president and a principal of Severud Associates, New York City, at SEAoNY's annual meeting in New York City, Oct. 24. "This data could be in the form of photographs, observations of specific structural or fire damage, or any other technical information that may be useful to the study," said DePaola.

SEAoNY hopes to get a rotation of about 20 engineers, 10 for each salvage yard, rotating on approximately an every third day basis, for the next two months. If anything of interest is found, the engineers would ask the salvage yard to set it aside until members of the study team can determine its value, said DePaola. He is one of six SEAoNY members on the ASCE team, which made its first field trip to Ground Zero Oct. 12-18.

At the SEAoNY meeting, ASCE President H. Gerard Schwartz Jr. and DePaola announced that SEAoNY has become a study sponsor. Others include the Federal Emergency Management Association, Washington, D.C.; the American Institute of Steel Construction Inc., Chicago; the American Concrete Institute International, Farmington Hills, Mich.; the National Fire Protection Association, Quincy, Mass.; and the Society of Fire Protection Engineers, Boston.

During the WTC's original construction period, each piece of tower steel was stamped with its location in the building. Saw-Teen See, ASCE team member and managing principal of the local Leslie E. Robertson Associates, a successor firm to the WTC's structural engineer of record, has provided information on the markings that identify the steel for those areas under particular scrutiny. Of special interest are members at the airplane impact and fire floors, said DePaola. The approximate impact floors are, for One WTC, the north tower, 94 to 99; for Two WTC, the south tower, 78 to 84.

SEAoNY has, since Sept. 11, organized 397 engineer-volunteers to assess the stability of debris and other affected structures during the rescue, recovery and debris removal efforts, including performing rapid damage assessments for more than 400 area buildings. The teams are under the direction of LZA/Thornton-Tomasetti, the local structural engineer under contract to the city's Dept. of Design and Construction (DDC).

At the meeting, DePaola asked for similar photographs, observations and other data from SEAoNY volunteers on the buildings still standing immediately surrounding, but outside, the WTC site. Some of the buildings are also under study by the ASCE team.

The city has reduced the size of the cordoned-off zone around the WTC site and "handed" many area buildings back to their owners. The Dept. of Buildings could not be reached for a specific list, but reports are that the 54-story One Liberty Plaza, directly across Church Street from the site, has reopened.

Even with their first full day off Oct. 28 to allow victims' families to gather for a memorial service at Ground Zero, workers are making steady cleanup progress. As of Oct. 29, they had removed 449,876 tons of debris, including 89,664 tons of steel. The city has signed a contract with a new steel recycler in Keasbey, N.J., says George Wittich, senior vice president of Weeks Marine Inc., which is handling steel debris removal. He says the recycling market is "absorbing" all the steel so far. But officials may shut down daily operation of one of four large steel removal cranes. Located at Manhattan's southern tip, its operation has faced traffic hazards with site and commercial vehicles. The crane would be on "reduced standby," says one official.

City officials also confirm that Turner Construction Corp., one of WTC's four prime contractors, could wrap up cleanup work as early as this week. "They have removed Building 7," says one official. "It is absolutely gone." But the firm is set to be retained to handle project-wide planning and scheduling. DDC is also set to return to the city a public school used as cleanup headquarters since Sept. 11 and move operations to the American Express building at World Financial Center.

As of Oct. 30, crews from Nicholson Construction Co., Pittsburgh, working to stabilize the foundation walls for the substructure "bathtub" that surrounds the twin tower footprints, had installed and grouted 12 tieback anchors, and tested and tensioned 8 up to full design. "The design is successful and there is minimum wall movement when tensioning," reports Peter Rinaldi, engineering program manager for the Port Authority of New York & New Jersey, which owns the land and developed the site.