This report deals with the passive fire protection used in the World Trade Center (WTC) towers. The main objective is to provide background information that can be used to assess the in-place conditions of the passive protection before and after aircraft impact. The report includes a review of key building code provisions related to structural fire protection. It also includes a review of key decisions related to passive fire protection made during design, construction, and occupancy of the towers. Copies of documents to support key findings are included in an Appendix. A summary is provided of available data on in-place measurements of the sprayed fire-resistive materials (SFRMs) applied to the floor trusses and to core members. Measurements of thermoplastic properties of the passive fire protection materials, including gypsum panels, are presented. The effects of gaps in thermal insulation and the effects of variability of insulation thickness are evaluated. The rationale for selecting the effective thickness of thermal insulation for use in thermal-structural analyses is presented. Measurements of adhesive and cohesive strengths of a selected SFRM are summarized. Simplified models are presented for estimating the acceleration required to dislodge SFRM from planar surfaces and encased round bars. The report concludes with a summary of key findings.
Citation: NIST NCSTAR - 1-6A
Pub Type: NIST Pubs
World Trade Center, high rise buildings, building collapse, disasters, fire safety, fire investigations, terrorists, terrorism, fire protection, fire resistance, thermal response, thermophysical properties, adhesive strength, building codes, cohesive strength, construction, density effects, thickness, heat capacity, fire resistive materials, thermal conductivity, thermal insulation