Sensitivity of composite floor system response at elevated temperatures to structural features

• Composite floor system response to fire is examined in a 24 factorial sensitivity study.
• Floor beam length, shear studs, connection type, and lateral framing of girders are evaluated.
• Effect of the structural features are evaluated for impact on time to damage and failure onset.
• Floor beam length and connection type most influenced the structural response of the floor system.
• A broader view of the interaction of fire types and composite floor features needs to be considered.

The sensitivity of composite floor system response at elevated temperatures to variations in structural features is examined in a sensitivity study based on a 24 factorial design. Four structural features were varied between two values, based on the NIST investigation of the WTC 7 collapse. The effects of the four parameters, as well as their interaction effects, are evaluated relative to time to onset of damage and time to failure for the structural features.Structural features that affected the response were ranked according to their influence. Of the four structural features varied in the analyses, floor beam length and connection type most influenced the structural response of the floor system, sometimes changing the time to damage onset or failure by more than 0.5 h. The presence or absence of girder studs and one- or two-sided girder framing influenced the structural response to a lesser extent. Interaction effects were apparent in the structural response, indicating that the structural features cannot be evaluated independently when considering the response of a composite floor system to fire effects.The findings suggest that a broader view of the impact of heating and cooling phases of fire types (standard fires, compartment fires, and traveling fires) that are used for evaluating the performance of composite floor systems needs to be considered, particularly with regards to floor lengths, connection types, and restraint of thermal expansion.