基于受压区分区破坏机制的有腹筋RC梁受剪承载力公式

由于钢筋混凝土(RC)梁传力机理的复杂性和剪切破坏模式的多样性,现有受剪承载力公式的计算精度随受剪参数的变化呈现出明显的波动性,限制了其适用范围。以混凝土受压区的分区破坏机制为基础,从防止纵向钢筋提前屈服的角度建议受压区高度的修正公式,由此得到同时兼容低强和高强混凝土梁的混凝土剪切贡献表达式。通过斜裂缝倾角的转动规律分析混凝土与箍筋协同工作机制发挥的不同阶段,并据此建议箍筋项的剪切贡献计算原则。建立基于受压区分区的有腹筋RC梁受剪承载力公式。该公式以分项的形式直接体现剪压区、斜拉区和箍筋三部分的剪切贡献,能够反映混凝土强度、配箍率、纵筋率、剪跨比以及尺寸效应等主要受剪参数的影响规律。最后,基于剪切试验数据库对所提公式和当前主流公式进行验证,并对各公式的预测精度和参数敏感性进行对比评价。研究结果表明:所提出的受压区分区破坏机制能够较好地反映剪切破坏模式随剪跨比变化的演变规律;建议的受剪承载力公式具有较高的精确性和稳定性,对受剪参数的大范围变化不敏感,且对高强、大尺寸试件具有更好的适用性。

Shear Strength Formula for RC Beams with Stirrups Based on Distinct Failure Mechanism in Rezoned Compression Zone

Because of the complexity of transfer mechanisms and the diversity of shear failure modes of reinforced concrete (RC) beams, the accuracy of current shear capacity equations fluctuates obviously with variations in shear parameters, and the scope of these equations is limited. Based on the distinct failure mechanism in concrete compression zone (CCZ), a modified formula for the height of CCZ was proposed in this study from the perspective of preventing early yielding of longitudinal reinforcement, and the concrete shear expression compatible with both low- and high-strength RC beams is obtained. Second, through the rotation law of diagonal crack angle, different stages of the cooperative working mechanism between concrete and stirrups were analyzed, and the calculation principle of the shear contribution of stirrups was proposed. Furthermore, the shear capacity formula of RC beams with web reinforcement based on rezoned compression zone was established. The sub-items of the formula directly reflect the shear contribution of three parts, namely, the shear compression zone, diagonal tension zone, and stirrups. In addition, the formula reflects the influences of the main shear parameters such as concrete strength, longitudinal reinforcement ratio, stirrup ratio, shear span to depth ratio, and size effect. Finally, based on a shear database, the proposed and current commonly used formulas were verified, and the prediction accuracy and parameter sensitivity of each formula were compared and evaluated. The results show that the adopted distinct failure mechanism in CCZ can reflect the evolution of shear failure modes with shear span ratio. The proposed shear capacity formula has higher accuracy and stability, is less sensitive to a wide range of changes in shear parameters, and has better applicability to high-strength and large-size specimens.