火灾后钢筋混凝土板力学性能评估方法∗

钢筋混凝土楼板是火灾中最容易破坏的结构构件，需要对其火灾后的承载能力进行评估并加固。考虑升温阶段、降温阶段及火灾后阶段材料本构关系的不同，考虑高温下混凝土保护层的爆裂对温度场及力学性能的影响，提出了火灾后钢筋混凝土楼板力学性能分析的有限元计算模型。同时，针对典型的钢筋混凝土板加固方法，在前述有限元模型的基础上建立了火灾后加固的钢筋混凝土板有限元计算模型，利用该模型对典型的火灾后加固钢筋混凝土板的承载能力进行了计算分析。模型中采用单元生死技术实现了混凝土高温下的爆裂及火灾后加固的数值模拟，模型可用于火灾后及加固后钢筋混凝土板力学性能的评估。分析表明，经历火灾后，钢筋混凝土板的承载能力降低幅度较大，板存在明显残余挠度。加固后，钢筋混凝土板的承载能力得到较大程度的恢复。

PostFire Mechanical Performance Evaluation Method of ReinforcedConcrete Slabs

Reinforced concrete (RC) slabs are among the most vulnerable structural components todamage in fires, necessitating the post-fire evaluation of their load-bearing capacity and subsequent re-inforcement. A finite element model for analyzing the post-fire mechanical performance of RC slabswas proposed. In this model, the variations in material constitutive relations during heating, cooling,and post-fire stages were considered. The impact of concrete protective layer spalling on temperaturedistribution and mechanical properties of the slabs under high temperatures was also taken into consid-eration. Building on this model, another finite element model for evaluating the load-bearing perfor-mance of RC slabs reinforced after fire exposure was also proposed. Both models employed element birth-death technology to simulate concrete spalling under high temperatures and post-fire reinforce-ment. The models could be used to evaluate the post-fire mechanical performance of reinforced RCslabs. The analysis revealed significant reductions in the post-fire load-bearing capacity of RC slabs,with noticeable residual deflection; however, reinforcement was able to substantially restore this capac-ity.