单裂缝简支梁动静刚度变化规律分析及试验研究

Analysis and Experimental Study on Dynamic and Static Stiffness Change Rules of Simply Supported Girder with a Single Crack

基于单裂缝Euler-bernoulli简支梁挠度及频率计算公式,讨论单裂缝简支梁的动刚度、静刚度变化规律以及两者间的关系,同时对4片矩形截面钢筋混凝土简支梁分级加载开展相关的试验研究。研究结果表明:位于振型节点的裂缝对动刚度无影响,应采用一阶频率计算动刚度;钢筋混凝土简支梁裂缝发育初期,动刚度、静刚度变化基本一致;裂缝进一步发育后,动刚度大于静刚度;钢筋混凝土简支梁开裂初期可用实测结构基频代替荷载试验了解结构的刚度情况,但梁体开裂严重时应谨慎使用此方法。

Based on the deflection and frequency calculation formulas of Euler-Bernoulli simple supported girder with single crack,the dynamic and static stiffness change rules of single crack simple supported girder and their relationship were discussed. At the same time,the related experimental study on four rectangular section reinforced concrete simple supported girders under step loading was carried out. The results show that the cracks at the mode joints have no effect on the dynamic stiffness,so the first-order frequency should be used to calculate the dynamic stiffness. The dynamic stiffness and static stiffness of reinforced concrete simple supported girders are basically the same at the initial stage of crack development. The dynamic stiffness is greater than the static stiffness after further crack development. The stiffness of reinforced concrete simple supported girders can be understood by the measured structural fundamental frequency instead of the load test at the initial stage of cracking,but this method should be used cautiously when cracking of beams is serious.