基于提离模型的基础隔震结构支座拉应力研究

Research on Bearing Tensile Stress of Base Isolation Structure Based on Bearing Lift-off Model

在隔震结构设计中橡胶支座的拉应力问题至关重要.为研究隔震支座在出现拉应力后的受力状态,提出了一种支座提离行为假定,将提离状态概括为一种受力平衡的减支座体系,实现提离状态的简便解法.类比偏压构件提出适于衡量倾覆效应大小的荷载等效偏心率概念,采用转换系数统一表达各荷载组合,从而得到较简明的表达式.推导了各受力阶段的等效偏心率、支座内力和应力、整体转角的解析式,提出支座临界平均面压要求,计算了有关的高宽比限值.结果表明,支座拉应力主要受水平地震作用、高宽比、支座性能及布置形式的影响;在8度(0.2g)、8度(0.3g)、9度(0.4g)地区,允许支座出现拉应力时等效偏心率限值分别为0.24、0.22、0.20,相应的高宽比限值分别为4.5、3.5、2.5.

The tensile stress of rubber bearings is critical for the design of isolated structures.To study the force state of isolation bearings after the occurrence of tensile stresses,a hypothesis of bearing lift-off behavior is proposed,and the lift-off state is summarized as a force-balanced bearing reduction system,thus obtaining a straightforward solution for the lift-off state.The concept of load equivalent eccentricity,which is suitable for measuring overturning effect,is proposed by analogy with eccentric compression members,and a conversion coefficient is adopted to express load combinations uniformly,so as to obtain a more concise expression.The analytical formulas of equivalent eccentricity,internal force and stress of bearing and overall rotation angle at each stress stage were derived.The critical average compressive stress of bearing was proposed,and the corresponding height-width ratio limits were calculated.The results show that the tensile stress of the bearing is mainly affected by horizontal earthquake action,height-width ratio,bearing performance and arrangement;in the area of 8 degrees(0.2g),8 degrees(0.3g),9 degrees(0.4g),the limit of the equivalent eccentricity when the bearing is allowed to have tensile stress is 0.24,0.22,0.2,respectively,and the height-width ratio limits is 4.5,3.5,2.5,respectively.