火灾下邻边简支邻边固支双向板极限承载力的能量计算法

AN ENERGY METHOD FOR CALCULATION THE LOAD-CARRYING CAPACITY OF TWO-WAY SLABS WITH TWO EDGES SIMPLY SUPPORTED AND TWO EDGES CLAMPED IN FIRE

对2个足尺邻边简支邻边固支钢筋混凝土双向板试件进行了抗火试验,介绍了试验炉及试件设计、试验方案及观测内容和方法,描述了试验现象、裂缝及邻边简支邻边固支钢筋混凝土双向板的破坏特征,研究了受火过程中沿板厚度的温度场分布规律及板的竖向和水平变形,分析了受火过程中固支边的内力重分布;试验结果表明,未受火面裂缝最终形成半椭圆形破坏模式。在试验基础上,给出了火灾作用下邻边简支邻边固支钢筋混凝土双向板极限承载力的新能量法计算模型,该模型假定火灾作用下板的张拉薄膜效应在塑性铰线形成后出现,且张拉薄膜效应为塑性铰线上屈服钢筋伸长所做塑性功提供。该模型计算结果与试验结果吻合很好,而基于塑性铰线理论的传统能量法计算值偏保守。

Fire-resistant experiments were conducted on two full-scale reinforced concrete two-way slabs with two edges simply supported and two edges clamped.This paper presents the design of the furnace and specimens,the test plan,the measuring contents and methods.The test phenomena,cracking and failure characteristics of the tested reinforced concrete two-way slabs were described.The temperature distribution along the depth of the slab,vertical deflection and horizontal displacement have been studied.Internal force redistribution of the clamped edges has been analyzed.The results indicated that the cracks on the unfired side of the slab formed a semielliptical pattern.Based on the experimental results,a new energy method for the limit load-carrying capacity calculate of concrete slabs with two edges simply supported and two edges clamped in fire conditions was presented.The model assumed that the tensile membrane effect of the slabs showed only after the formation of plastic hinge lines,and was caused by the plastic work done by the reinforcement elongation at the yield line section.Comparison between the developed model and test results showed good correlation,while the classical energy method based on the yield line theory gave a conservative value.