混凝土连续板火灾后力学性能试验及理论分析

Experimental research and theoretical analysis on the post-fire mechanical performance of the continuous concrete slabs

为研究受火跨位置和数量对混凝土连续灾后板力学行为影响,对一块常温连续板和五块混凝土灾后连续板开展力学性能试验,分析灾后板裂缝、变形、混凝土和钢筋应变以及灾后破坏模式等规律。基于塑性铰线理论,提出混凝土双向板破坏模式和椭圆方程,推导板块内力平衡方程,建立灾后板剩余承载力计算方法,并与其他方法计算结果进行对比分析。结果表明,相比常温板屈服线延性破坏模式,灾后板易出现脆性破坏,即加载点或内支座处冲切破坏,特别是爆裂严重工况。相比混凝土或钢筋应变破坏准则,变形破坏准则l/50更适用于确定灾后板剩余极限承载力。此外,本文方法可用于确定灾后板剩余极限承载力,计算结果偏于保守。对于灾后板,应分别采用弯曲理论和冲切理论进行剩余承载力分析,两者最小值可作为剩余极限承载力。

To investigate the effect of the number and position of the fire-damaged spans on the post-fire behavior of the continuous concrete slabs,the strength tests on one reference slab and five fire-damaged slabs were carried out,and then the post-fire cracks,deflections,concrete and steel residual strains and failure modes were analyzed.Based on the yield line theory,the failure mode and elliptic equations of two-way concrete slab were proposed,and the equilibrium equations of internal forces were established to analyze the carrying capacities of the fire-damaged slabs.The comparison of analysis results between the present method and other methods was also conducted.Results show that different from the yield ductile failure mode of the reference slab,the fire-damaged slab easily tends to fail in the brittle failure mode,including the punching shear failure at the loading point or at the internal support,particularly the serious spalling case.Compared to the strain failure criteria of concrete and steel,the deflection failure criterion l/50 was suitable for determining the residual limit loads of the fire-damaged slabs.In addition,the present method can be used to determine the residual limit carrying capacity of the fire-damaged slab,and the predicted results were relatively conservative.For the fire-damaged slab,the flexural theory and the punching shear theory shall be used to determine the residual carrying capacity of the fire-damaged slab respectively,and the minimum value can be regarded as the residual limit load.