矩形混凝土空心墩延性抗震性能试验研究

为深入认识混凝土空心墩地震损伤机理并评估其延性能力，对不同剪跨比、纵筋率及配箍率的方形和矩形空心墩试件开展拟静力加载试验. 观测各墩裂缝分布和损伤情况，分析桥墩的滞回性能、曲率及位移延性，并结合文献试验数据探讨既有塑性铰公式对空心墩顶部位移能力计算的适用性. 研究结果表明:各空心墩试件呈弯曲破坏特征，延性系数均在5.0以上，抗震性能良好；相同剪跨比下空心墩抗剪性能弱于相同外尺寸实心墩；增加纵向率能够适当提升空心墩侧向承载力和极限位移；在低轴压比下，纵筋率和箍筋用量对空心墩位移延性系数的影响规律不明显；空心墩塑性铰长度随剪跨比、纵筋强度或直径、轴压比的增加而提高，随混凝土强度的增加而降低，而配箍率的影响不显著；Mander、孙治国和JRA塑性铰模型预测值与试验值误差不超过5%，其中Mander公式计算效果最佳，可用于评估空心墩等效塑性铰长度；规范中较多采用的Paulay-Priestley模型高估了空心墩塑性铰长度，会使得桥墩抗震设计偏于不安全. 

Experimental Study on Ductile Seismic Performance of Rectangular Hollow Concrete Columns

To deeply explore the seismic damage mechanism and evaluate the ductile capacity of hollow RC columns, square and rectangular hollow specimens with different aspect ratios, longitudinal rebar ratios, and stirrup ratios were tested under quasi-static loading. The crack distribution and damage state were observed. The hysteretic behavior, curvature and displacement ductility were analyzed. According to the experimental data in literature, applicability of the existing plastic hinge formulas to estimate the tip displacement capacity of hollow columns was discussed. The results show that all hollow specimens suffer flexural failure with ductility factor over 5.0, resulting in excellent seismic performance. The shear performance of hollow columns is weaker than that of solid members with the same external size and aspect ratio. The lateral bearing capacity and ultimate displacement can be properly improved by increasing longitudinal rebar ratio. However, the longitudinal steel and stirrup amount exert vague effects on the displacement ductility factor of hollow columns with low axial load ratio. The plastic hinge length of hollow columns increases with increased aspect ratio, longitudinal rebar strength/diameter, or axial load ratio, but decreases with the increment in concrete strength. The influence of stirrup on the plastic hinge is not obvious. The relative errors between the test and calculation of Mander, Sun and JRA models are less than 5%. Mander supplies the best result, which can be used to evaluate the equivalent plastic hinge length of a hollow column. The Paulay-Priestley model, adopted in many codes, overestimates the length of the plastic hinge of hollow members, leading to unsafe seismic design.