Improved tensile membrane action model of composite slabs at elevated temperatures

Abstract

Previous fire testes have showed that tensile membrane action (TMA) between composite slabs and reinforced concrete slabs is different. An improved TMA model is proposed in this paper to accurately and reasonably determine the fire resistance of composite slabs exposed to ISO834 fire. It is assumed that the fracture of steel reinforcement in the long span is the governing failure mode of composite slabs at elevated temperatures. The slab is divided into four concrete rigid plates and one elliptic reinforcement net at centre considering TMA, and the contribution of rotation of concrete rigid plates on the deflection in short-span is taken into account. Meanwhile, coupling thermo-mechanical finite element analyses are carried out to simulate the TMA response of composite slabs at elevated temperatures. The accuracy of the proposed improved model is validated against experimental and numerical results, with a maximum error within 10%. It is found that the improved model has a better prediction of the mid-span deflection and fire resistance than Li’s model and Bailey’s model. It is important to consider the stress redistribution of the reinforcement in two directions in determining TMA in composite slabs under fire conditions.