跨海大桥半装配式组合桥墩设计及抗震性能试验

Design and Seismic Performance Test of Semi-assembled Composite Piers for Sea-crossing Bridges

为研究采用外包超高性能混凝土(UHPC)的钢管(ST)作为免拆模板,内浇普通混凝土(NC)的组合桥墩的抗震性能,以罗屿大桥为工程背景,开展了UHPC-ST-NC组合桥墩结构设计,并制作了3个不同设计参数的组合桥墩(编号URST-1、UHST-1、UHST-2)和1个整体现浇钢筋混凝土(RC)桥墩(编号ZT-1)。通过开展桥墩试件的拟静力试验,分析各试件的破坏模式,对比各试件的滞回曲线、骨架曲线、延性性能、耗能能力、刚度退化等性能指标,并采用Abaqus有限元软件分析UHPC径厚比和钢管径厚比参数对组合桥墩的抗震性能的影响。结果表明:采用UHPC-ST模板取代钢模板的设计方案,不仅能提高桥墩的耐腐蚀能力和耐冲刷能力,并且节省了拆模的时间,提高了施工效率;UHPC-ST-NC组合桥墩在地震作用下的破坏模式与整体现浇桥墩类似,均为压弯破坏,但其破坏程度明显轻于整体现浇桥墩;与ZT-1试件相比,URST-1、UHST-1、UHST-2试件的峰值荷载分别提升了56.9%、68.0%、69.6%,水平承载能力更高;峰值位移也分别提升了11.8%、24.2%、68.0%,残余位移更小,耗能能力更强;带有构造箍筋的UHPC-ST-NC组合桥墩的延性系数、极限位移、耗能能力均高于无构造箍筋的UHPC-ST-NC组合桥墩;根据有限元参数分析结果,建议UHPC-ST-NC组合桥墩截面UHPC径厚比取0.2~0.3,钢管径厚比取0.01~0.015。试验结果表明,UHPC-ST-NC组合桥墩的抗震性能优于整体现浇桥墩,在钢管外侧焊接水平环向箍筋能提高桥墩的抗震性能。

This study investigated the seismic performance of combination piers using steel tubes(STs)encased with ultra-high-performance concrete(UHPC)as a demolition-free formwork with normal concrete(NC)cast inside.With the engineering background of Luoyu Bridge as the motivation for the study,a structural design of UHPC-ST-NC combined piers was carried out.Three combined piers with different design parameters(labeled as URST-1,UHST-1,UHST-2)and one monolithic cast-in-place reinforced concrete(RC)pier(labeled as ZT-1)were fabricated.A static test of the bridge pier specimens was conducted,and the damage mode of each specimen was analyzed.Subsequently,the hysteresis curve,skeleton curve,ductility performance,energy dissipation capacity,stiffness degradation,and other performance indexes of each specimen were compared,and the effects of the diameter-thickness ratios of UHPC and steel pipes on the seismic performance of the combined bridge pier were analyzed using the Abaqus finite element software.The results show that the use of the UHPC-ST formwork instead of a steel formwork can not only improve the corrosion resistance and scour resistance of bridge piers but also save the time required for demolding and improve the construction efficiency.Furthermore,the damage mode of the UHPC-ST-NC combined piers under seismic action is similar to that of the overall cast-in-place piers.Both pier types show compression and bending damage,but the damage degree of the combined piers is significantly lower than that of the overall cast-in-place piers.Compared with ZT-1,UHST-1,UHST-1,and UHST-2 exhibit the same damage mode as that of the overall cast-in-place piers.The peak load of URST-1,UHST-1,and UHST-2 is 56.9%,68.0%,and 69.6%higher than that of ZT-1,respectively,which results in a higher horizontal load carrying capacity.Meanwhile,the peak displacements are 11.8%,24.2%,and 68.0%higher,respectively,which result in a smaller residual displacement and a higher energy-consuming capacity.In addition,the ductility coefficients,ultimate displacements,and energy-consuming capacities of the UHPC-ST-NC combined piers with structural hoops are higher than those of UHPC-ST-NC combined piers without structural hoops.According to the results of finite element parameter analysis,it is suggested that the diameter-thickness ratio of the UHPC section of the UHPC-ST-NC combined pier should be 0.2-0.3,that of the steel pipe should be 0.01-0.015.The test results show that the seismic performance of the UHPC-ST-NC combined pier is better than that of the whole cast-in-situ pier,and that the welding of the horizontal circular hoop reinforcement at the outer side of the steel pipe can improve the seismic performance of the bridge pier.