Thermal and structural response of a two-story, two bay composite steel frame under fire loading

Abstract

The collapse of the World Trade Center Towers and other recent fires in tall buildings has motivated a study to understand the performance of structural frames under fire loading. A two-storey, two-bay composite steel frame was constructed and was subjected to dead loads using load blocks, and to thermal load by placing the frame in a furnace. The furnace was specially designed to allow for controlled heating of the structural elements that form the various compartments of the test frame. This paper describes the experimental results of a furnace test conducted on three full-scale composite frames. The three tests differed from each other in the number of compartments that were heated by the furnace and in the relative location of the heated compartments. For each test, the structural elements were subjected to a heat-up phase followed by a cool-down phase. The furnace temperatures as well as the steel and the concrete temperatures recorded during the test are discussed. The thermally induced horizontal displacements and vertical deflections of the various structural elements are presented. Observations on local buckling of the steel beam, cracking of the concrete slab and failure of the beam-to-column connection are tabulated. Experimental results of the three tests are compared and contrasted by studying the complete deformation process of the test frames over time. Results indicate that the deformation process and time to failure of a structure is highly dependent on the number of compartments that are heated and the relative location of the compartments that are subjected to fire loading.