混凝土空心墩塑性铰区抗剪计算模型比较分析

Comparative Analysis of Shear Strength Models in Plastic Hinge Region for Concrete Hollow Piers

准确评估空心墩塑性铰区的抗剪能力是高墩大跨桥梁抗震设计的重要内容.目前国内外规范中并未明确给出空心墩的抗剪计算模型,规范中已有的实心墩抗剪公式能否直接应用、其它文献中实心墩或空心墩抗剪强度计算方法的适用性等均有待深入研究.为此,基于25个发生剪切或弯剪破坏的空心墩试验数据,分析塑性铰区抗剪能力的影响因素,并将抗剪强度试验值与已有15个抗剪公式计算结果进行比较.结果表明:混凝土空心墩抗剪能力随混凝土强度、配箍率和轴压比的增加而提高,一定范围内随位移延性系数和剪跨比的增加而降低,纵向配筋率的影响不显著;Aschheim、Caltrans、Sezen和Shin公式的计算值与试验结果误差不超过5%,其中Sezen模型计算效果最佳,可用于评估空心墩塑性铰区抗剪能力;NZS3101、JRA、JTG/TB 02-01—2008、Eurocode 8和ACI-318等规范公式计算结果略显保守,可作为空心墩抗剪设计的依据;其余公式过高估算了抗剪强度,不适于混凝土空心墩塑性铰区的抗剪设计.

Accurate evaluation of shear strength in plastic hinge region is of great significance for seismic design of long-span bridges with tall piers.However,the shear design models for hollow piers are not directly listed in the current codes in China and abroad.The applicability of both the existing formulas for solid piers in the codes and the formulas for solid or hollow columns in literature needs to be further studied.Thus,based on the test results of 25 hollow piers with shear or flexural-shear failure modes,the influencing factors of shear strength in plastic region are analyzed,and the experimental values of shear strength are compared with the calculation results of 15 formulas.The results show that the shear strength of concrete hollow piers increases with an increase in concrete strength,stirrup ratio and axial load ratio,and decreases with an increase in displacement ductility factor and aspect ratio within a certain range,while the influence of the longitudinal reinforcement ratio is not significant.The errors between the test results and the calculated values by formulas of Aschheim,Caltrans,Sezen and Shin are all less than 5%,among which the Sezen model is the most suitable to assess the shear strength in plastic hinge region for hollow piers.The formulas in NZS3101,JRA,JTG/TB 02-01—2008,Eurocode 8,and ACI-318 lead to slightly conservative results,which can be used for shear design of hollow piers;the rest of equations,for overestimation of the shear strength in plastic hinge region,are inappropriate to concrete hollow piers.