火灾下钢结构建筑楼板的薄膜效应机理及理论模型

通过试验及火灾实例发现,建筑结构中的钢筋混凝土楼板或压型钢板组合楼板在高温下能产生很大变形,进而产生薄膜效应,能大大提高楼板的抗火性能。因此,在结构防火设计中正确考虑薄膜效应的影响,对发挥楼板的抗火潜能,降低结构抗火成本,有重要意义。本文论述了火灾下楼板的薄膜效应产生的机理,建立了分析模型,将楼板划分为5部分,包括周边4个刚性板块和中间一呈椭球面的板块。分别对板块的内力和弯矩进行了分析,然后根据板块内力及弯矩的平衡方程及位移协调方程,推导出了火灾下考虑薄膜效应后楼板极限承载力的计算公式,为考虑薄膜效应时的楼板抗火设计提供了参考。

Mechanism and theoretical model of membrane action in slabs of steel buildings subjected to fire

Observations of experiments and fire-caused damages in real buildings indicate that membrane action plays an important role in enhancing the fire-resistant capacity of floor slabs.Therefore,if it is taken the membrane action into account,the potential load bearing capacity of floor slabs in fire condition can be exploited and the fire protection cost can be reduced.In this paper,the mechanics of the membrane action is introduced and a model is proposed,in which a floor slab is divided into five parts,including four rigid peripheral plates and an ellipsoidal part.Based on this model,forces and moments in each part are analyzed.Finally,according to the force equilibrium and geometric accordance function,the approach of calculating the limit load bearing capacity of floor slab with membrane action in fire condition is proposed.