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首页> 外文期刊>Earthquake Engineering & Structural Dynamics >Accidental torsion due to overturning in nominally symmetric structures isolated with the FPS
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Accidental torsion due to overturning in nominally symmetric structures isolated with the FPS

机译：由于FPS隔离的名义对称结构的倾覆而导致的意外扭转

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摘要

Overturning of a structure causes variations in the normal loads of the isolators supporting that structure. For frictional isolators, such variation leads to changes in the frictional forces developed and, hence, in the strength distribution in plan. For frictional pendulum system (FPS) isolators, it also causes changes in the pendular action, i.e. in the stiffness distribution of the isolation interface. Therefore, although the structure is nominally symmetric it develops lateral-torsional coupling when it is subjected to two horizontal components of ground motion. This coupling is denoted herein as accidental torsion due to overturning, and its effect in the earthquake response of nominally symmetric structures is evaluated. Several parameters are identified to control this coupling, but the most important are the slenderness of the structure and the aspect ratio of the building plan. Results are presented in terms of the torsional amplification of the deformations of the isolation base and the interstorey deformations of the superstructure. The FPS system is modelled accurately by including true large deformations and the potential uplift and impact of the isolators. Impulsive as well as subduction-type ground motions are considered in the analysis, but results show small differences between them. An upper bound for the mean-plus-one standard deviation values of the torsional amplifications for the base due to this accidental torsion is 5%. This implies that for design purposes of the isolation system such increase in deformations could probably be neglected. However, the same amplification for the interstorey deformations may be as large as 50%, depending on the torsional stiffness and slenderness of the superstructure, and should be considered in design. In general, such amplification of deformations decreases for torsionally stiffer structures and smaller height-to-base aspect ratios.
机译：结构的倾覆会导致支撑该结构的隔离器的法向载荷发生变化。对于摩擦隔离器，这种变化会导致产生的摩擦力发生变化，从而导致平面强度分布发生变化。对于摩擦摆系统（FPS）隔离器，它也会引起摆动作的变化，即隔离界面的刚度分布。因此，尽管该结构名义上是对称的，但当它受到地面运动的两个水平分量时，会产生横向扭转耦合。这种耦合在这里表示为由于倾覆引起的意外扭转，并评估了其在名义对称结构的地震响应中的作用。确定了几个参数来控制这种耦合，但是最重要的是结构的细长度和建筑平面图的纵横比。根据隔震基础变形的扭转放大和上部结构的层间变形，给出了结果。通过包括真实的大变形以及隔离器的潜在隆起和冲击，可以对FPS系统进行精确建模。分析中考虑了冲动型和俯冲型地震动，但结果表明它们之间的差异很小。由于这种偶然的扭转，基座的扭转放大率的平均值加一标准偏差值的上限为5％。这意味着，出于隔离系统的设计目的，这种变形的增加可能会被忽略。但是，层间变形的相同放大率可能高达50％，这取决于上部结构的扭转刚度和细长性，在设计时应予以考虑。通常，对于抗扭刚度较高的结构和较小的高度-基础纵横比，变形的这种放大减小。

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