圆形钢筋混凝土桥墩等效塑性铰长度

Equivalent plastic hinge length of circular reinforced concrete bridge columns

基于桥墩极限位移三分量模型,从弯曲、剪切和纵筋滑移变形等三方面分析了桥墩塑性铰长度的主要影响参数;通过40个圆形钢筋混凝土桥墩试验数据的分析,建议了桥墩塑性铰长度的理论公式及经验公式;并对建议及各规范的塑性铰长度公式进行了模型桥墩、足尺桥墩和实桥桥墩的验证。结果表明:钢筋混凝土桥墩塑性铰长度主要随墩高、截面高度、材料特性参数(fydb/fc')及纵筋率的增大而增大,与轴压比、配箍率等关系不大;与试验结果相比,就平均意义而言,各国规范塑性铰长度计算结果偏于安全,但均有较大的离散性,日本JRA规范最为保守,中国《公路桥梁抗震设计细则》(JTG/T B02-01—2008)较美国Caltrans规范及欧洲Eurocode8规范保守;建议的塑性铰长度理论公式与日本JRA规范相当,建议的塑性铰长度经验公式在平均意义上与美国Caltrans规范及欧洲Eurocode8规范一致,但具有较小的变异系数和较高的保证率,优于其他公式。

Based on the three-component ultimate displacement model, principal influence factors of plastic hinge length are analyzed considering the bending, shear and bar-slip deformations. The theoretical formula and empirical formula for equivalent plastic hinge length of bridge column are suggested based on the test results of 40 circular reinforced concrete bridge columns. The formulae of plastic hinge length proposed by authors and other specifications are validated by scale and full-scale reinforced concrete bridge column experiments. The results show that the equivalent plastic hinge length of bridge column increases most consistently with specimen length, section height, fydb/√f＇c and longitudinal reinforcement ratio, while independent on the axial-load ratio and the transverse reinforcement ratio. From the point of the average statistical meaning, these expressions of plastic hinge length of existing specifications are conservative but discrete. The recommended expression in JRA specification is most conservative, and JTG/T B02-01-2008 Specification gives more conservative results compared with Caltrans and Eurocode8 specifications. The proposed theoretical plastic hinge length is approximate to that in JRA Specification. The proposed empirical expression is statistically close to Cahrans and Eurocode8 with smaller variation coefficient .and higher guaranteed rate.