Control of Shear Failure of Reinforced Concrte Member Subjected to Combined Load

采用先进的空间桁架理论，研究了钢筋混凝土构件在弯、扭、剪共同作用下的极限承载力和破坏模式。然后，采用钢筋混凝土板模型对受扭构件的变形性能进行了分析。调查结果在各章节中描述如下。(1)钢筋混凝土弯扭剪复合受力构件的极限承载力和破坏模式本文提出了以空间桁架理论为代表的扭转问题的计算方法，将扭、弯、剪力叠加，导出了基本方程。用迭代法计算了任意载荷组合下的应力和应变，并进行了破坏校核。在扭转和弯曲下的破坏模式分为1）横向杆的屈服，2）对角混凝土支柱的压碎，3）压缩区域的压剪断裂和4）弯曲断裂。计算结果与试验结果的对比表明，该方法能有效地预测混凝土的极限承载力和破坏模式。(2)钢筋混凝土受扭构件的变形性能首先对钢筋混凝土板假定了有效抗扭截面。在此基础上，从混凝土的平衡协调条件出发，推导出考虑拉应力的基本方程。采用建议的混凝土保护层剪应变指标，通过混凝土的有效保护层来估算开裂后区域的刚度折减。在分析中，使用迭代方法。计算值较好地反映了矩形截面和T形截面的整体变形特性。

The ultimate strength and failure modes of reinforced concrete member subjected to combined torsion, bending and shear are investigated by the advanced space truss theory. Then, deformation behavior of members under torsion is estimated by RC plate model. The results of investigation are described as follows in each sections.(1) Ultinate strength and failure modes of reinforced concrete member subjected to combined torsion, bending and shearThe space truss theory as typical method for torsional problems is advanced by superposing torsional, bending and shear force, and fundamental equations are derived. By using an tierative method stress and strain for an arbitrary combination of loads are calculated and checked to failure. Failure modes under torsion and bending are classified as 1)yielding of transverse bars, 2)crushing of diagonal concrete struts, 3)compressive-shear fracture of compressive region and 4)flexural fracture. According to the comparison of calculated values and results of experiments, the proposed method is available to ptedict the ultimate strength and failure mode.(2) Deformation behavior of reinforced concrete member subjected to torsionAt first, effective cross section against torsion is assumed to reinforced concrete plates. Then fundamental equations are derived from equilibrium compatibility conditions considering tensile stress of concrete. Reduction of stiffness in post cracked region is estimated by effective cover of concrete using the proposed index of shear strain at cover. In analysis, an iterative method is used. Calculated values estimate finely whole deformation behavior of rectangular sections and T-shaped sections.