基于塑性铰模型的钢筋混凝土桥墩地震损伤评价

SEISMIC DAMAGE EVALUATION OF RC BRIDGE COLUMNS BASED ON PLASTIC HINGE MODEL

塑性铰模型已被日本JSCE、美国Caltrans、新西兰NZS和中国(征求意见稿)等国家的桥梁抗震规范采纳,用于评价钢筋混凝土桥墩的位移(延性)能力。随着基于性能/位移抗震设计理论的发展,相继提出了残余位移、极限曲率及曲率延性系数、纵筋和混凝土的最大应变、纵筋低周疲劳损伤等桥墩地震损伤量化指标。选用5种常用塑性铰模型,通过数值分析和试验数据对比研究了利用塑性铰模型对上述损伤指标进行估计的准确程度及主要影响因素。结果表明:塑性铰模型计算的滞回曲线及残余位移和试验结果十分接近,但会高估桥墩最终破坏时纵筋的最大拉应变,低估核芯混凝土的最大压应变;对剪跨比λ≥8的(高)桥墩计算的极限曲率小于试验值,可能会导致偏于不安全的设计结果;在最大加载控制位移相同条件下,加载方式对上述损伤指标的计算结果影响较小。

A plastic hinge model has been widely used in bridge aseismic design codes such as Japan, Caltrans, New Zealand and China （revised edition）, to evaluate deformation capacity or the displacement ductility factor of RC bridge columns. With the development of bridge performance/displacement based aseismic design, several damage indices have been suggested, such as the ultimate curvature and curvature ductility factor of critical section, maximum strain of confined concrete and reinforced steels, low cycle fatigue damage indices of longitudinal reinforcement etc. To study the accuracy degree of damage indices calculated with plastic hinge models and the main influencing factor, a computer program was developed employing 5 plastic hinge models to compute aforesaid damage indices compared with the test data of RC bridge columns. The study results show that force-displacement curves and residual deformation calculated match the experiment with adequate accuracy, but the strain of longitudinal steel is overestimated and the strain of core concrete is underestimated. The computed ultimate curvature is lower than that of experiment results when shear span ratio is not less than 8. It is also recognized that under the same loading control displacement, loading path hardly affects the aforesaid damage indices.