Analytical Investigation of Fire Loads for Steel-Framed Open-Deck Parking Structures

This paper describes research directed towards the development of realistic fire loads for steel-framed, open-deck parking structures. The research is part of a broader effort at Lehigh University to determine fire loads for structural design. This paper focuses on typical framing plans proposed in the AISC Design Guide 18: Steel-Framed Open-Deck Parking Structures. Seven fire scenarios were developed considering five framing plans from the Design Guide 18. Vehicle fires were simulated using Fire Dynamics Simulator (FDS), a computational fluid dynamics program developed by the National Institute of Standards and Technology (NIST). The objective of the fire analyses was to observe the transmission of heat through the structure and the heat flux input to the structure. Analysis parameters, including framing geometry, floor elevation, and vehicle fire characteristics, were varied to investigate their effects on fire loading. The results of the fire analyses were subsequently used to conduct non-linear heat transfer finite element analyses in order to determine the temperature distribution through structural framing members in the vicinity of the vehicle fire(s). The computed steel temperatures corresponded to reductions in the effective yield strength of the steel and the tension capacity of the bottom flange of the framing member adjacent the vehicle fire(s) as great as 12% for single-vehicle fire scenarios and 88% for the multiple-vehicle fire scenario considered.