An analysis of the WTC fires using CIB correlations and simple modeling

Abstract

CIB correlations for compartment burning rates and average gas temperatures are examined for accuracy, utility, and generality. The results are applied to modeling the fire on 9/11 in WTC 1. Specific information is used from the NIST investigation. It is demonstrated that simple heat transfer modeling can predict the truss steel rod temperatures for the E119 tests of WTC done by NIST. The CIB temperature correlation and steel truss modeling are used to predict burning conditions for the WTC 1 96th floor fire and compared to the NIST results. Here a consideration of fuel loads from 20 to 40 kg/m2 was considered compared to just 20 used by NIST. The results suggest that the fully insulated truss bar temperatures would achieve higher values for higher fuel loads. A critical steel truss temperature of 650°C could support failure of the trusses as a theory for the collapse of the towers.