火灾后混凝土楼盖剩余承载力试验及理论研究

为了研究混凝土楼盖火灾后承载性能和破坏模式,对三块灾后楼盖和两块常温楼盖开展力学性能试验,获得了混凝土楼盖裂缝、破坏模式、变形、混凝土和钢筋应变等发展规律。基于塑性铰线理论,考虑梁刚度和变形对楼盖极限承载力的影响,建立了灾后楼盖剩余承载力和破坏模式计算方法,并与试验结果进行对比。结果表明：灾后和常温楼盖不同承载机制致使两者破坏模式略有不同,分别表现为板先破坏模式和梁先破坏模式,除了弯曲破坏,灾后楼盖中板格易发生冲切破坏；相比配筋方式,配筋率对楼盖极限承载力有更为重要影响,随着板格配筋率提高,极限承载力增加,但发生脆性破坏可能性增加；传统简支板和固支板屈服线理论,倾向于低估或高估楼盖承载力,本文方法所得楼盖极限承载力计算结果较为合理。

Experimental and Theoretical Research on the Post-fire Mechanical Performance of the Concrete Beam-slab Specimens

To investigate the post-fire residual capacity and failure mode of the concrete beam-slab specimens, the mechanical tests of three fire-damaged specimens and two reference specimens were conducted, and the cracks, the failure modes, the deflections, the concrete and steel strains were observed during each test. Based on the conventional yield line method, the stiffness and deflection of the beam was considered to establish the theoretical method, and the residual ultimate load and failure modes of the specimens can be analyzed, and the predicted results were compared to the experimental results. Results show that different mechanism of the reference and fire-damaged specimens led to different failure modes, including the first panel failure and the first beam failure. In addition, apart from the flexural failure, the punching failure mode of the fire-damaged specimen also occurred. Compared to the reinforcement layout, the reinforcement ratio has considerable effect on the ultimate loads of the beam-slab specimens, increasing the reinforcement ratio of the panel led to its higher carrying capacity and the brittle failure easily appeared. The conventional simply-supported and fixed yield line method tended to underestimate or overestimate the ultimate loads of the specimens, and the present method can reasonably predict the ultimate loads of the beam-slab specimens.