考虑压拱效应的钢筋混凝土双跨梁竖向承载力分析

钢筋混凝土框架结构在使用期内遭遇爆炸、撞击等突发事件时，可能引起结构承重柱失效，从而导致结构倒塌。当失效柱为内柱时，失效柱上方与其相连的两跨梁将形成双跨梁，双跨梁的承载能力决定剩余结构的抗倒塌能力。为分析双跨梁的受力特征和破坏机理，进行了3根1/4缩尺钢筋混凝土双跨梁的静力加载试验。结果表明：梁端存在轴向约束时，梁产生压拱效应，其竖向承载力得到提高；基于试验结果，根据双跨梁关键截面满足的内力平衡方程、考虑压拱效应时满足的变形协调方程，推导出梁的竖向荷载与中柱竖向位移之间的关系式；通过不断增大竖向位移，得到最大竖向荷载(对应的梁轴向力为压力)即为双跨梁考虑压拱效应的竖向承载力。理论分析结果和试验结果比较表明，所提计算方法有较高精度。

Vertical bearing capacity of RC two-bay beams considering compressive arch action

Important buildings may be subjected to accidental loads, such as explosions or impacts, during their service life. For reinforced concrete (RC) frame structures, columns on the first floor are more prone to failure, compared with other components. The performances of the newly formed two-bay beams above the failed columns were determined the resistance capacity against progressive collapse of the structure. In order to investigate the mechanical characteristics and failure mechanism of the two-bay beams, tests of three 1/4-scaled RC rectangle beam-column subassemblies were carried out. It was observed that the compressive arch action was activated and the peak value of the vertical load was improved due to the compressive arch action. Based on the test results, the method to determine the vertical bearing capacity of RC two-bay beams was proposed. According to the equilibrium equations of the internal forces at the key sections of the beam, the compatibility equations of deformation, the relation between the vertical load and the deflection of the middle joint of the two-bay beam were derived. By increasing the deflection of the beam step by step, the vertical bearing capacity of the two-bay beam considering the compressive arch action can be yielded, which is taken as the maximum vertical load of the beam in the calculation. The proposed method was verified to be effective by comparing the calculated and test results.