摘要
橡胶支座是连接桥梁上下部结构的重要构件,其力学性能对上下部结构地震响应有重要影响,但其力学性能会因安装时采用的锚固边界条件的不同而存在差异。为研究不同边界约束对橡胶支座受力性能的影响,利用有限元软件建立了顶底面锚固、顶面锚固和顶底面均不锚固(无锚固)3种不同边界约束的精细化橡胶支座有限元模型,并通过试验及理论计算验证了所建有限元模型的合理性。随后对具有不同边界约束的支座有限元模型施加竖向力及剪切变形,对比分析了不同边界约束对支座内部应力分布、应力响应值变化等力学性能的影响。结果表明,随剪切变形的增加,支座因受压面积减小而导致内部峰值压应力逐渐增加,不同边界约束下支座的内部峰值压应力增加幅值相差明显,其中采用顶底面锚固的支座增加幅值最大,无锚固边界支座增加幅值最小;在剪切变形作用下,对橡胶支座采取锚固措施会增加支座内部应力响应值,相同水平荷载下,顶底面锚固支座比无锚固支座更易发生橡胶层与钢板间的剥离、撕裂破坏,而且采取顶底面锚固边界约束会增大桥梁结构下部地震力,不利于结构抗震;对于采用无锚固边界约束的支座,随剪切变形的增加,其刚度退化明显,在设计时应考虑因支座支承面处卷曲而造成的有效剪切面减小的影响。
As an important component connecting the superstructure and the substructure of bridge, the mechanical property of rubber bearings has an important influence on the seismic response of the superstructure and the substructure, but the mechanical property is different depending on the anchorage boundary conditions adopted in the installation. In order to investigate the influence of different boundary conditions on the mechanical property of rubber bearings, a group of refined FE models of the bearing, which considering anchoring at top and bottom surfaces, only anchoring at top surface and without any anchoring, are developed using finite software. The rationality of all the finite models is verified by comparing with the experimental result and theoretical result. Then, vertical stress and shear deformation are applied on the verified models, the influence of different boundary conditions on the mechanical property, such as inner stress distribution and stress response value, is comparatively analysed. The result shows that(1) The compressive area of bearings decrease as shear deformation increase, which lead to the internal peak compressive stress increase gradually. The obvious different increases of peak compressive stress depend on the boundary condition. The bearing with anchoring at top and bottom surfaces increases the maximum amplitude, while the bearing without any anchoring increases the minimum amplitude value.(2)The internal stress value of bearings will be increased with anchoring application under shear deformation. The bearing with anchoring at top and bottom surfaces is more prone to peel and tear damage between rubber layer and steel plate than that without any anchoring under the same horizontal load, and the seismic force transferred to the substructure of bridge will be increased with anchoring application, which is not good for seismic performance of bridge.(3) For the bearing without any anchoring, the stiffness will be degraded as shear deformation increase. It is recommended that the decrease of effective shear area of bearings caused by roll-off at the supporting surfaces should be taken into consideration during bridge design stage.
引文
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