ULTIMATE LOAD OF SLABS IN FIRE ENHANCED BY TENSILE MEMBRANE ACTION WITH FLEXIBLE SUPPORTING EDGE BEAMS

摘要

A number of previous analytical studies have been conducted to predict the enhanced load-bearing capacity of slabs due to tensile membrane action.These analytical approaches are based on an implicit assumption that vertical supports along the slab panel boundaries at all times during afire do not deform.In reality the edge beams do deform even though they are fire-protected, and thus this assumption may be nullified.This renders their predictions to be unconservative when there is significant deflection of protected edge beams.This work looks at the actual condition where the protected supporting edge beams do deflect, and the slab still bends in synclastic curvature.The authors propose a semi-analytical model which can predict the load-bearing capacity of the composite beam-slab floor systems under fire conditions enhanced by tensile membrane action, but reduced by deflection of the protected edge beams.Its feature is that the deflection of the protected edge beams can be taken into account of calculation of the slab enhancement factor.