基础隔震结构高宽比限值研究

本文研究目的是得到隔震结构在各种工况下的高宽比限值,这对隔震结构设计是必要的。橡胶隔震支座不能产生拉应力和隔震支座压应力不超过容许值是保证隔震结构在强震中不产生倾覆的充分条件。基于这两个条件,本文推导了隔震结构高宽比限值的显式并给出了针对不同建筑类别、不同设防烈度、不同场地条件和不同隔震层阻尼比的高宽比限值。在支座的轴力计算中,考虑了水平地震作用、竖向地震作用和重力荷载代表值的共同影响以及荷载的最不利组合。研究发现,当控制条件为支座不产生拉应力时,高宽比限值随隔震结构周期的增加而增加;当控制条件为支座压应力不超过容许值时,高宽比限值随隔震结构周期的增加而减小。因此,存在一个临界周期使高宽比限值取得极大值。研究还发现,存在一个最大的隔震结构周期使高宽比限值等于零或隔震层位移超过容许值。将隔震结构的周期与临界周期和最大隔震周期比较,就可以得到相应高宽比限值的表达式。

Research on the height-width ratio of base isolated structure

The objective of this study is to obtain the height width ratio of base isolated structure with rubber bearings under different working cases, as it is necessary for the seismic design of this kind of structure. The research work is based on the two preconditions, which are the sufficient conditions to keep the base isolated structure from overturning during strong earthquake. One precondition is that the tensile stress cannot be appeared in the rubber bearings and the other is the compression stress of the rubber bearings cannot exceed the allowable value. The details and the results of the height width ratio explicit formulas are presented corresponding to different building categories, earthquake fortification intensities,site classifications, and damping ratios of isolated story. The influences of the horizontal seismic action, vertical seismic action and gravity load design value are all considered in the expressions of the axial forces of the rubber bearings. And the axial forces of rubber bearings are calculated according to the most unfavourable load combinations. It is found that the height width ratio increases with the isolated structure period when it is restricted by the first precondition, and decreases when restricted by the second one. So there exists a critical period, at which the height width ratio reaches its maximum value. It is also found that there exists a maximum isolated structure period at which the height width ratio is zero or the displacement of the rubber bearing exceeds the allowable value. In comparison of the period of the base isolated structure with the critical and maximum period, the height width ratio can be obtained by the corresponding formulas.