Towers' Wind-Force Design Questioned

Towers Wind-Force Design Questioned
Engineers who designed the World Trade Center may have significantly underestimated the force of the winds that the twin towers needed to withstand in the worst of possible storms, federal investigators said yesterday, an oversight that could have led to weaker-than-needed exterior steel columns.

That design decision, although inconsequential for three decades, perhaps shortened the time that tenants and rescue workers had to evacuate the towers before they collapsed on Sept. 11, 2001.

The finding, which the engineers dispute and that investigators acknowledge needs more study and may turn out to be unfounded, was among dozens of interim conclusions released yesterday as a two-year study on the collapse of the twin towers neared a conclusion.

The report, released yesterday by the National Institute of Standards and Technology in Boulder, Colo., includes detailed photographs that identify, for the first time, the exact spots where the exterior steel columns gave way. These critical zones were around the 81st floor in the south tower, near the offices of Fuji Bank, and near the 96th floor of the north tower, where Marsh & McLennan was based.