The Effect of LITS on Punching Shear in Fire

Abstract

Several recent sets of experimental results on the punching shear behavior of flat slabs in fire have produced apparently anomalous deflections results, where the slab deflections on heating are in the opposite direction to that expected. Using numerical analysis, this paper shows that the results are explained by load induced thermal strains (LITS). Using two independent modelling approaches, the profound effect of LITS on deflection behavior is demonstrated. Analysis of the strain state near column connections identifies significant differences when LITS is included in analyses. By contrast for the unrestrained slabs considered here, stress states do not change much. The potential implications of these findings for design are noted.