System level response of braced frame structures under fire exposure scenarios

This paper examines the stability of a braced frame steel structure under realistic fire, loading and restraint scenarios. A set of numerical studies are conducted on a three-dimensional model of a 10-story steel frame building with perimeter V bracing using the finite element software, ABAQUS. The effect of critical parameters such as the location of fire, type of fire exposure and spread of fire from one compartment to another on the stability aspects, as well as fire performance of the structure at the system level is examined. A nonlinear dynamic explicit analysis is carried out to simulate the response beyond stages of a local member failure. At each time step, the calculated stresses, deflections, and axial forces are checked against the failure limit states under strength, deflection, and stability criterion. In addition, following an initial member failure, the progression of the load path towards collapse is monitored. Results from the analysis infer that the likelihood of progressive collapse and global failure time depends significantly on the location and type of fire exposure in a steel framed building. Results also show that the prescriptive fire rating for structural members, as per the current code provisions, may not be conservative under certain severe fire exposure scenarios.