Experimental evaluation of floor slab contribution in mitigating progressive collapse of steel structures

摘要

As a result of several high-profile terrorist attacks against buildings in recent years, mitigating progressive structural collapse has been of particular interest to the structural engineering community. Previous research studies have focused on the impact of an individual column failure on the overall stability of a structure. These studies have relied mostly on computational investigations and experimental tests on individual components. Few studies have been done to predict the behavior of floor slabs above a failed column, and the computational tools used have not been validated against experimental results. The research program presented in this paper extends prior work in this area by testing specimens that include all structural components of a typical floor system in a prototypical steel-framed structure. In total, six full-scale tests will be performed, including three interior 2-bay × 2-bay specimens and three exterior 2-bay × 1-bay specimens. In all tests, the mid-span column will be removed statically while the slab is loaded with the recommended extreme event design load. The slab consists of corrugated decking with lightly reinforced concrete on top that is connected to the floor beams through shear studs and is consistent with typical building practices in the US. The first test is planned for the summer of 2012. The extensive computational analyses that have been done so far indicate the significant contribution the slab has in sustaining overall building stability and mitigating collapse. Initial analysis results show that the contribution of the corrugated decking acting compositely with the concrete slab is significantly greater than that of the floor beam grillage. The significant contribution of the corrugated decking is attributed to the membrane forces that are developed while the deflections increase. Preliminary analyses suggest that the slab in the test structure can sustain the removal of the mid-span column without collapsing. These models, however, require assumptions that must be validated against test data. Therefore, results from the tests will provide valuable information for validating analysis models and developing recommendations for improving current design practice.