密肋复合墙板框格单元破坏模式研究

框格单元是密肋复合墙板的基本受力单元,为了详细研究框格单元的破坏过程、破坏模式及填充砌块与框格的相互作用机理,进行了3个框格单元的单调对角加载试验。试验表明:加载过程中首先在填充块对角线附近出现一至二条贯通的主拉裂缝;接着框格上、下节点及框格梁柱上出现垂直裂缝;填充块上下角区出现圆弧状受压裂缝后框格单元达到承载力极限状态,其最终破坏形式与填充块和框格相对刚度有关。基于弹性地基梁理论分析了加载过程中框格和填充材料的受力特点,指出框格单元存在三种破坏形式:砌块对角压碎破坏、砌块角部压碎破坏、肋柱肋梁节点局部受压破坏。其中第二种形式与复合墙板的各阶段破坏形式相对应,且塑性铰转动充分,是一种合理的破坏模式。最后结合试验及理论分析将填充块等效为铰接于框格的对角斜压杆,提出等效斜压杆宽度、强度和刚度的计算方法,建立单元格简化分析模型,为墙板的受力分析提供了理论基础。

Research on failure mode of fundamental frame structure in multi-ribbed composite wall

Fundamental frame structure is the basic mechanical element of multi-ribbed composite wall(MCW).Three specimens are tested under monotonic diagonal load in order to study the failure process,failure mode and interaction mechanism between concrete frame and infill.Experiments show that: one or two principle tensile cracks are produced near the diagonal of the infill at first;then vertical cracks appear in the ribbed beam-column and the joint;fundamental frame structures reach to ultimate bearing capacity after circular arc compression cracks appear in the angle region of the filling block.The final failure pattern is related to relative stiffness between infill and ribbed beam-column.Force behaviors of concrete grid and infill in loading process are analyzed based on elastic foundation beam theory.Three distinct failure modes are categorized diagonal compression mode,corner crushing mode and ribbed beam-column local compression mode.Among them,the second failure mode is in accordance with different failure stage of MCW,meanwhile the plastic hinges rotate fully,and it's a reasonable failure mode.The experiments and theoretical analysis show that effect of the infill can be equaled as hinged-diagonal strut.Formulas of width,strength and stiffness of the strut are presented,and simplified calculation model is established to simulate mechanical properties of the fundamental frame structure in elastic stage,which offers a theoretical basis for analysis the MCW.