不同剪切变形下橡胶隔震支座竖向压缩刚度试验研究

针对橡胶隔震支座,研究了其在不同水平剪切变形状态下的竖向压缩刚度理论计算方法,基于双弹簧模型,提出了改进的不同剪切变形状态下橡胶隔震支座竖向压缩刚度理论计算公式。采用建筑结构中常用的第二形状系数S 2=5系列(G4)天然橡胶支座及铅芯橡胶支座,进行了不同压应力及不同剪切变形下的压缩性能试验,通过试验研究不同水平剪切变形状态下的橡胶隔震支座竖向压缩刚度。研究结果表明:橡胶隔震支座竖向压缩刚度随剪应变增大而减小,随设计压应力增大而增大;在设计压应力相同的条件下,橡胶隔震支座竖向压缩刚度随压应力变化范围的增大而减小;基于橡胶隔震支座有效承载面积的公式虽能反映支座竖向压缩刚度随剪应变增大而减小这一趋势,但与试验结果相比误差较大;既有的基于双弹簧模型的竖向压缩刚度计算公式计算精度优于基于有效承载面积的竖向压缩刚度计算公式,但在150%以上剪应变时,也存在误差较大的问题;提出的改进的基于双弹簧模型的不同剪切变形状态下橡胶隔震支座竖向压缩刚度计算公式与试验结果吻合较好,与既有基于有效承载面积计算橡胶隔震支座竖向压缩刚度和基于双弹簧模型的计算橡胶隔震支座竖向压缩刚度的公式相比较,具有较高的计算精确度。

Experimental study on the vertical compressive stiffness of rubber isolation bearings under different shear deformation

For rubber isolation bearings in isolated structures,the theoretical calculation methods for its vertical compression stiffness under different horizontal shear deformation were studied,and based on a two-spring model,an improved theoretical calculation formula for the stiffness was presented.Compressive property tests under different compressive stress and different shear deformation for linear natural rubber bearings and lead rubber bearings of S 2=5 series(G4)commonly used in building structures were carried out and the vertical compression stiffness of rubber isolation bearings under different horizontal shear deformation was investigated by experiments.The results show that the vertical compressive stiffness of the bearing decreases with the increase of shear strain and increases with the increase of design compressive stress.Under the condition of the same design compressive stress,it decreases with the increase of the changing range of compressive stress.Although the calculation based on the effective bearing area of the bearing can reflect the trend that the vertical compression stiffness of the bearing decreases with the increase of shear strain,there is a big error between the calculation and test results.The calculation method based on the two-spring model has better calculation accuracy compared with that based on the effective bearing area of the bearing,however,there is also a big error when the shear strain is not less than 150%.The improved calculation formula for the vertical compression stiffness of rubber isolation bearings under different horizontal shear deformation presented in the paper can get the results in good agreement with the experimental results and has better calculation accuracy compared with conventional calculation methods based on the two-spring model and based on the effective bearing area of the bearing.