Fire structure interface and thermal response of World Trade Center towers

Abstract

Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, w/hichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).

Thermo-mechanical Analysis of Fire Doors Subjected to a Fire Endurance Test

“…The only loads that were applied to the structural model were derived from the thermal results and gravity. Though not addressed here, the transfer of thermal data to the structural model in cases where a single software package is used is very streamlined [26].…”

“…This one-way coupling allows the solution of the thermal analysis to be completed first without consideration of the structural response. The structural analysis can be solved after reviewing and validating the thermal results [26].…”

A sensitivity study on the fire-induced heating of concrete slabs in composite floor systems

“…The temperature-dependent thermophysical properties of steel (thermal conductivity, density, and heat capacity) are taken from Ref. 3. The concrete thermophysical properties (thermal conductivity, density, and heat capacity) are taken from Ref.…”

Effects of Thermal Expansion and Support Restraints on Performance of Composite Floors in Fire

“…For concrete thermal conductivity the value is varied from 1.5 W/(m.K) at 25 o C to 1.00 W/(m.K) at 1200 o C and for specific heats it is from 880 J/(kg.K) at 25 o C to 1500 J/(kg.K) at 1200 o C. The lightweight concrete of the two specimens was designed for a density of 1600 kg/m 3 (100 pcf) at ambient temperature, which is different from that of the concrete reported by Prasad and Baum (2005). Therefore, for this analysis, the concrete density was reduced from 1600 kg/m 3 at 20 o C to 1300 kg/m 3 for 1200 o C. The reduction function was selected as those of the lightweight concrete used by Prasad and Baum (2005). Moisture content of concrete was obtained as 51 kg/m 3 , based on the reported 70% relative humidity, 0.23 chemically bound water, 237 kg (522lb) cement, and concrete water mix of 127 kg (281 lb).…”

“…As for concrete, thermal properties were derived from the study results reported by Prasad and Baum (2005). Appendix A of the report provides these properties at different temperatures for the lightweight concrete.…”