方钢管约束混凝土桥墩拟静力试验

Quasi-static test of concrete-piers confined by square steel tube

为研究不同约束形式及混凝土墩身与承台间的连接构造对桥墩试件的抗震性能和各项指标的影响规律,设计1根采用混合接头连接的装配式方钢管约束混凝土桥墩试件(SYP-GT4试件)、1根方钢管约束的整体现浇混凝土桥墩试件(SYZ试件)和1根方形截面的整体现浇混凝土桥墩试件(SFZ试件)。在桥墩墩帽处采用位移加载方式完成构件的拟静力试验,观察试件的破坏过程以及破坏模式,分析了桥墩的破坏形态、荷载-位移滞回曲线、荷载-位移骨架曲线、延性、耗能等特征参数。结果表明,3根混凝土桥墩试件的破坏形态基本一致,二者均为整体压弯破坏模式。SYZ试件与SFZ试件相比,水平峰值荷载提高了46.5%,滞回耗能能力更优,均有很好的延性性能,表明方钢管约束的整体式桥墩抗震性能优于现浇混凝土桥墩;SYP-GT4试件与SYZ试件相比,水平峰值荷载数值相接近,位移延性系数提高了24.1%,残余位移小,变形恢复能力较优,滞回曲线呈现更饱满的梭形,无明显捏缩,连接构造对强度和刚度退化的影响较小,两者抗震性能接近。

To study the impact of different restraint methods and the connection structure between concrete piers and caps on the seismic performance and various indicators of bridge pier specimens,three experimental setups were designed:one featuring a prefabricated square steel tube confined concrete pier(SYP-GT4 specimen),another with a square steel tube confined integral cast-in-place concrete pier(SYZ specimen),and a third with a square section integral cast-in-place concrete pier(SFZ specimen).The pseudo-static test was carried out on the pier caps using displacement loading method,and the failure processes and modes of the specimen were closely observed.Various characteristics,including failure modes,load-displacement hysteretic curves,load-displacement skeleton curves,ductility,energy dissipation and other relevant parameters of the piers were analyzed.The results show that all three concrete pier specimens exhibited similar failure modes,characterized by integral failure due to compression and bending.Notably,SYZ specimens outperformed SFZ specimens with a 46.5%increase in horizontal peak load,superior hysteretic energy dissipation capacity,and better ductility,indicating that integral bridge piers constrained by square steel tube demonstrate superior seismic performance compared to cast-in-place concrete piers.Furthermore,when comparing SYP-GT4 specimens to SYZ specimens,they exhibited a similar horizontal peak load value,a 24.1%increase in displacement ductility coefficient,minimal residual displacement,and enhanced deformation recovery capabilities.The hysteresis curve showed a fuller spindle shape without obvious pinching.The connection structure has little effect on the degradation of strength and stiffness,and their seismic performance is similar.