Mechanism of Resistance and Rational Design Method of Reinforced Concrete Structures Subjected to Torsion

在本研究中，可以得出以下结论：1。对钢筋混凝土梁在扭转作用下的受力特性进行了分析研究。所采用的解析方法的特点是将梁的原实体截面等效为空心截面，并将施加的扭转转化为均匀剪切流。对于混凝土的应力-应变关系，考虑了混凝土的软化、拉筋和沿裂缝的剪切传递。钢筋局部屈服的影响也被纳入分析。提出的解析方法可以较好地预测钢筋混凝土梁受扭的极限强度和一般变形特性。混凝土覆盖层对受扭混凝土梁的极限扭矩和变形行为有显著影响，因为覆盖层混凝土的抗拉性能、混凝土支撑的抗压性能、抗剪流深度受混凝土覆盖层深度的影响较大。大混凝土盖层混凝土梁的空间桁架在极限状态下不形成，裂缝数量少，裂缝分布不太好。在这种混凝土梁中，计算的极限扭矩被高估了。提出了钢筋混凝土梁在扭弯复合荷载作用下的极限扭矩计算方法。当钢筋混凝土梁承受较大的弯曲荷载时，这种方法与扭转相比低估了极限扭矩。即使在大截面预应力钢筋混凝土梁中，极限扭矩也随着预应力量的增加而增加，其极限状态的剪切流量（ql和qw）几乎相同，纵钢和箍筋的钢比（pl和pw）也相同。预应力筋在极限扭矩处的应变与在预应力处受拉的预应力筋的应变基本相同，因此JSCE法计算的极限扭矩高估了预应力钢筋混凝土梁的极限扭矩，特别是在预应力较小的情况下。少

In this study, the following results can be drawn.1. Analytical studies on the mechanical behaviors of reinforced concrete beams subjected to torsion were carried out. The characteristics of the employed analytical method were to assume the original solid section of beam to be equivalent to a hollow one and convert the applied torsion into a uniform shear flow. Concerning the stress-strain relation of concrete, the softening, the tension stiffening and the shear transfer along cracks were considered. The effect of the local yielding of reinforcement was also incorporated into the analysis. It was admitted that the ultimate strength and general deformation behavior of reinforced concrete beams subjected to torsion could be predicted fairly well by the proposal analytical method.2. Cover of concrete has a significant effect on the ultimate torque and deformation behaviors of concrete beams subjected to torsion, because the tensile resistance of cover concrete, the compressive resistance … More of concrete strut and the depth of shear flow were largely affected by the depth of concrete cover. The space truss was not formed at the ultimate state in the concrete beams with large concrete cover, in which the number of cracks was small and the distribution of cracks was not so good. In such concrete beams, the calculated ultimate torque was overestimated.3. The calculating method of the ultimate torque of reinforced concrete beams subjected to the combined load of torsion and flexure was proposed. This method underestimated the ultimate torque, when the reinforced concrete beams were subjected to large flexural load compared to torsion.4. The ultimate torque increased with the amount of prestress even in the prestressed reinforced concrete beams with large section, where the shear flows (ql and qw) at the ultimate state were nearly the same and the steel ratios (pl and pw) of longitudinal steel and stirrup were also the same. The strain of prestressing bar at the ultimate torque was almost the same as that of prestressing bar tensioned at the prestressing, therefore the ultimate torque calculated by the JSCE method overestimated that of prestressed reinforced concrete beam, especially when the prestress was small. Less