Effects of slab panel vertical support on tensile membrane action
A recently-developed design method predicts composite slab capacities in fire, incorporating the effects of tensile membrane action. The method designs rectangular slab panels including unprotected beams within the panels, and are supported on edges that resist vertical deflection. In practice, vertical support is achieved by protecting the perimeter beams. Generic fire protection ensures that beam temperatures stay below critical temperatures of 550°C or 620°C within the required fire resistance time. However, large vertical displacements of the protected edge beams may cause a loss of the membrane mechanism, inducing single- curvature bending, which may lead to a catastrophic failure of the structure. A finite element investigation into the provision of adequate vertical support along slab panel boundaries has been conducted. The study has examined various degrees of protection relative to the development of the membrane mechanism. Comparisons are made with the membrane action design method and various acceptance criteria.