DOB Findings and Recommendations for WTC, Feb 2003

NYC 9/11 Public Portal Document

3 Sources of Information

3.1 FEMA Building Performance Study Report The Building Performance Study (BPS) Report, written by the Building Performance Assessment Team (BPAT), made a number of preliminary conclusions regarding the events of September 11th. Significantly, the steel framing system, egress stairways and their marking, and evacuation I training were all cited as contributing to the successful evacuation of most building occupants. Several design features, however, were identified as needing more detailed evaluation in order to understand their contribution to the performance of the WTC buildings and how they may perform in other buildings. These included: r I 1 • the overall strength of the floor truss system; • the susceptibility of fire proofing to blasts and impacts; • the inability of stairway enclosures to resist impacts; • and the concentration of emergency stairways in the central building core. Several other issues were found to be critical to building performance in one or more of the WTC buildings and the surrounding structures: • The redundancy and/or robustness of structural framing systems. • Adherence of fireproofing under impact and fire conditions. • Performance of structural connections under impact and fire loads. • The reliability of water supply to sprinklers. • Capacity and robustness of egress systems when building damage occurs. • Robustness of structural transfer systems during fires. The BPAT concluded that these features should be evaluated in detail to determihe how they affect the performance of the World Trade Center buildings and how they might perform in other buildings and situations. In addition to detailed technical analysis, the study team felt that extensive technical, policy, and economic examination of these concepts should be conducted prior to making specific building code revisions.

In the absence of sufficient data to determine the likelihood of any particular threat, the study team also recommended that individual building owners consider their own level of risk and investigate possible ways to enhance the redundancy and robustness of their structures. Indeed, the marketplace has already recognized this need and begun to voluntarily take additional precautions in instances of high. risk. I

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Page 16 WTC Building Code Task Force February 2003 Findings and Recommendations I

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