The building performance at the World Trade Center complex has been
described in considerable detail (Federal Emergency Management Agency,
2002), and only select features of the building response are described herein.
On September 11th, two hijacked aircraft were flown into the World Trade
Center towers. At 8:46 a.m. the north face of the north tower (WTC 1) was
struck, and at 9:03 a.m. the south face of the south tower (WTC 2) was struck.
At 9:59 a.m. and 10:29 a.m., WTC 2 and WTC 1, respectively, collapsed.
Figure 1 shows the area of the collapse debris impact as depicted by
FEMA (2002). Buildings surrounding the towers are also shown, with special
emphasis (dark shading) provided for those that were destroyed as a
consequence of being struck and/or ignited by debris from the collapsing
towers. The inner circles indicate the approximate radius of inner steel column
collapse and other heavy debris. The outer circles indicate the approximate
radius of fallen aluminum cladding and other relatively light debris. Of
special interest for electric power and telecommunications are WTC 7 and the
Verizon Building located along Vesey St. immediately north of the World
Trade Center complex.
Figure 2 is a map of the buildings surrounding the complex as published
by FEMA (2002). The map shows the damage assessment of surrounding
structures based on the inspections of 406 buildings on September 14 and 15
by New York City structural engineers. The building inspection procedures
and damage classification were adopted from guidelines developed for rapid
assessment of buildings after earthquakes (ATC, 1989).
As noted above, the damage to buildings was of unparalleled proportions
for a disaster perpetrated independently of official military operations. Of
significance also was the damage sustained by other civil infrastructure
systems, which are described briefly in the following sections of this paper.
Water Supply
The New