中小跨径梁桥横向混凝土挡块模型及参数影响分析

Effect analysis of mechanical models and parameters of shear keys of small-to-medium spanning highway bridges in transverse direction

为更准确地评估中小跨径梁桥主梁位移及下部结构地震响应,需建立合理的挡块分析模型。基于1座三跨预应力混凝土连续梁桥有限元模型,考虑了线弹性模型、考虑屈服的理想弹塑性模型及考虑退化的弹塑性模型3种不同挡块力学模型;对比分析了不同挡块模型对主梁位移及下部结构地震响应的影响;基于建议的分析模型,探讨了合理挡块间距的选取,并总结了有效防撞措施及新型挡块。结果表明,考虑退化的挡块模型可较好反映混凝土挡块在碰撞过程中的变形、损伤及完全失效的特性,而采用线弹性及理想弹塑性挡块模型都会低估主梁位移及高估传至下部结构的地震力;合理挡块间距选取范围在1.0~2.5 tr(橡胶层厚度)之间,可保证在橡胶支座发挥减隔震功能后,起到较好的限位作用,而又不致明显增加下部结构地震力。

To calculate the girder displacement and seismic responses of substructure more accurately for small-tomedium spanning highway bridges,reasonable analytical model of shear keys should be built. A three-span prestressed concrete continuous girder bridge was developed considering different analytical model of shear keys,which include linear elastic model,idea elastic-plastic model and mechanical model of shear key considering degradation.Influences on the girder displacement and seismic responses of substructure of different shear key models were discussed. Based on the recommended model,the reasonable initial gaps of shear keys were investigated. Then,some effective collision prevention measures and new-type shear keys were concluded. The results show that the mechanical model of shear key considering degradation can well simulate the deformation,damage status and disabling displacement limitation functionality under collision effects,while the linear elastic model and idea elastic-plastic model would underestimate the displacement of girder and overestimate the seismic forces transferred to substructure.The reasonable initial gaps of shear keys range from 1. 0 to 2. 5 tr( total thickness of rubber layer),which can be ensured that the displacement of superstructure can be restrained effectively by shear keys after the isolation function of rubber bearings working,and the seismic forces transferred to substructure will not be increased obviously.