火灾后四边简支钢筋混凝土板刚度与挠度试验研究及分析

为研究钢筋混凝土双向板在遭受火灾作用后的承载能力及挠度发展规律,对配筋率及受火时间不同的火灾后钢筋混凝土双向板承载能力进行研究。研究结果表明：火灾作用后,双向板在荷载作用下无混凝土开裂前的弹性阶段,而是直接进入带裂缝工作阶段,且只存在钢筋屈服前的带裂缝工作阶段和钢筋屈服后的破坏阶段；配筋率高的双向板挠度发展较为缓慢,具有更好的抵抗变形的能力,提高配筋率可使得双向板的抗弯刚度增加；随着受火时间的延长,双向板挠度发展加快,挠度曲线更为饱满,表明火灾使得双向板的抗弯刚度削减,挠曲变形也随之增大；以已有的受弯构件刚度的计算方法为基础,结合材料的高温后性能与火灾对双向板承载性能的影响,采用分层划分的方法,推导给出了火灾后钢筋混凝土双向板刚度及挠度计算公式,并与试验对比进行验证。

Experimental Study and Analysis on Stiffness and Deflection of Four-Sided Simply Supported Reinforced Concrete Slabs After Fire

In order to study the bearing capacity of two-way reinforced concrete slabs subjected to fire, the bearing capacity of r two-way reinforced concrete slabs with different reinforcement ratio and fire time after fire was studied. The results showed that: Under the action of load, there was no elastic stage before concrete cracking at the specimen after fire, and the specimens after fire directly entered the working stage with cracks. There were only the working stage with cracks before steel yield and the failure stage after steel yield in the test process. The deflection of specimens with high reinforcement ratio developed slowly and the ability of resisting deformation was batter. The bending stiffness of two-way slabs can be increased with the increase of the reinforcement ratio. The development of the deflection of the specimens was accelerated with the extension of fire time, and the deflection curve was fuller. The results showed that the bending stiffness can be reduced by the fire, and the deflection also increases. Based on the existing calculation method of stiffness and deflection of the flexural members, the method of layered division was adopted. Combined with the influence of the high temperature on the performance of the materials and the influence of fire on the bearing performance of the two-way slabs, the calculation method of the stiffness and deflection of two-way reinforced concrete slabs after fire was proposed. And the deflections of the test slabs were calculated and compared by using this formula.