钢筋混凝土梁的变幅滞回性能及其损伤评价

基于22根具有不同配筋率和配箍率的钢筋混凝土梁试件的变幅加载试验，研究钢筋混凝土梁的变幅滞回性能、承载力和加载刚度的衰变规律及其损伤评估方法，提出变幅滞回荷载作用下钢筋混凝土梁的损伤量化指标，分析了峰值位移、累积滞回耗能和加载历程对RC梁损伤的影响。研究表明：对于变幅滞回荷载作用下钢筋混凝土梁，耗能能力衰减指数、承载力衰减指数和加载刚度衰减指数的发展不完全同步，但三者都与历史峰值位移、累积滞回耗能有关；耗能能力衰减指数与承载力衰减指数呈波动型非单调增长，而加载刚度衰减指数呈单调增长趋势，因此加载刚度衰减指数更适合用来作为变幅滞回钢筋混凝土梁的损伤评价指标；当RC梁的延性系数较小时（k_,max< 3），其损伤与延性系数保持正相关关系，累积滞回耗能数量和峰值位移出现时点对这一关系影响甚微，而配箍率的增加能够明显降低RC梁的损伤。因此，控制延性系数并提高配箍率是控制RC梁地震损伤的一个稳定而有效的途径。

Damage evaluation of RC beams under variable amplitude loading histories

Based on the variable amplitude loading tests of 22 RC beam specimens with different stirrup ratios and reinforcement ratios, deterioration characteristics and corresponding prediction methods of energy dissipation capacity, loading capacity and loading stiffness for RC beam under variable amplitude loading histories were investigated. A seismic damage index was proposed to discuss the effects of maximum displacement, cumulative hysteretic energy and loading history on the damage. The research shows that, for RC beams under variable amplitude loading histories, the increasing of decay indexes for energy dissipation capacity, loading capacity and loading stiffness is not fully synchronized, but the three indexes are all related to the historic maximum displacement and the cumulative hysteretic energy. The increase of decay indexes for energy dissipation capacity and loading capacity with hysteretic cycles are non-monotonic increasing, but that for loading stiffness is monotonically increasing. Therefore, the decay index of loading stiffness is more suitable for damage evaluation. When the ductility coefficient of the RC beam is small (k_,max<3), the damage of the component is positively correlated with the ductility. The cumulative hysteretic energy and the maximum displacement appear to have little influence on this positive correlation, and the increase of the stirrup ratio can significantly reduce the damage under the same ductility conditions. Therefore, controlling the ductility coefficient and improving the stirrup ratio is a stable and effective way to control the seismic damage of RC beams.