车辆撞击下UHPC连接预制拼装桥墩动力响应及耐撞性能优化

Dynamic Response and Crashworthiness Optimization of Prefabricated Piers Connected by UHPC under Vehicle Impact

以UHPC连接预制拼装高架桥墩为研究对象,基于LS-DYNA软件对车辆撞击桥墩进行非线性有限元分析。通过UHPC试块轴压试验与落锤试验得到CSCM本构模型;并分析了不同撞击速度下预制拼装桥墩与整体现浇桥墩撞击力、变形发展规律及内力响应的异同;最后通过改变接缝钢筋直径,接缝处摩擦系数及下接缝处UHPC高度等关键参数进一步对预制拼装桥墩耐撞性能进行优化。结果表明:撞击后预制拼装桥墩的振动周期明显比整体现浇桥墩要短;拼装柱裂缝发展由墩底杯口上端向撞击背面延伸,整体柱则是从墩底延伸;两个桥墩的墩底易出现剪切破坏,被撞击处易发生弯曲破坏,其中拼装柱墩顶可能还会发生弯曲破坏,整浇柱墩顶易出现剪切破坏,拼装柱和整体柱抗撞性能差异不大;此外提高UHPC高度,相较于接缝钢筋直径和接缝处摩擦系数,对拼装柱耐撞性能提升最为明显,桥墩损伤破坏和动力响应也明显下降,可有效提升该桥墩的耐撞性能。

Based on LS-DYNA software,the nonlinear finite element analysis of vehicle impact piers was carried out based on UHPC connected prefabricated viaduct piers.Firstly,the CSCM constitutive model was obtained through the UHPC block axial compression test and drop hammer test.Secondly,the similarities and differences of impact force,deformation development law and internal force response between precast assembled piers and cast-in-place piers under different impact velocities were analyzed.Finally,the crashworthiness of precast assembled piers was furtherly optimized by changing the key parameters such as the diameter of joint reinforcement,the friction coefficient at the joint and the UHPC height at the lower joint.The results show that the vibration period of the precast piers after impact is obviously shorter than that of cast-in-place piers.The crack of assembled column develops from the upper end of the cup mouth at the pier bottom to the back side,while the integral column develops from the bottom of the pier.The bottom of two piers is prone to shear failure,and the place of impact is prone to bending failure.Among them,bending failure may occur on the pier top of assembled column,and shear failure may occur on the pier top of the whole cast column.There is little difference between the crashworthiness of assembled column and integral column.In addition,when the height of UHPC is increased,the crashworthiness of the assembled column is improved most obviously,compared with the diameter of the joint steel bar and the friction coefficient at the joint.The damage and dynamic response of the pier are also obviously reduced,which can effectively improve the crashworthiness of the pier.