基础隔震结构高宽比限值研究

Research on the limit value of height-width ratio of base-isolated structures

根据结构变形特点,提出基于Timoshenko理论的基础隔震分布参数体系模型,推导隔震结构高宽比限值计算公式,分析各参数对隔震结构高宽比限值的影响规律。分析表明,隔震结构和非隔震结构基本周期比值在一定范围内变化时,剪力系数、弯矩系数与周期比呈稳定曲线关系;高宽比限值随结构宽度方向布置支座个数增加而降低;在隔震支座总面积确定时,选择大直径隔震支座大间距布置方式可提高隔震层变形能力及高宽比限值;高宽比限值受竖向地震作用影响较小,随竖向地震系数增大高宽比限值略有降低;降低隔震层刚度、增大隔震层阻尼可提高结构高宽比限值;容许支座出现拉应力可在一定程度上提高结构高宽比限值。最后结合20层框剪结构工程算例,验证隔震结构高宽比限值公式的有效性。

According to the deformation characteristics of high-rise building, the equivalent continuous model was proposed based on Timoshenko theory. The dynamic properties of continuous structure subjected to random loads were studied. The overturning resistant performance and the limit of height-width ratio are analyzed for base-isolated structures. Based on dynamic characteristics of structure, the base-isolated cantilever Timoshenko beam was inves- tigated in this study as the simplified mode of regular structures. Vibration feature were derived from Timoshenko theory, and earthquake responses were calculated with the mode decomposition response spectrum method. The for- mula for calculating limit value of the height-width ratio of isolated structure was deduced, and the influence of dif- ferent parameters on the limit value of the height-width ratio was analyzed. The analysis indicated that shear force and moment coefficients and periodic ratio showed a stable curve when the basic period of isolation structure and seismic structure ratio changes within a certain range. The limit value of height-width decreased with the increase of the bearing number of end span. The limit value of height-width ratio was less affected by vertical earthquake, the ratio decreased slightly with the increase of vertical seismic coefficient. Reducing the stiffness of isolation layer and increasing the damping of isolation layer can increase the limit value of height-width ratio. The limit value of height- width ratio of isolated structure can be improved considering the tensile stress of bearings. Finally, the validity of limit value formula of height-width ratio of the isolated structure was indicated by the example of the 20 story frame shear structure engineering.