Seismic Torsional Effects In Multistory Buildings

本研究是由一个学术研究单位和一个专业设计办公室共同合作研究多层建筑的地震扭转效应。两个项目（BCS 9020394和BCS 9116089）合并为参考主题领域的联合合作研究，作为一个单一的研究工作。本研究采用解析模型和概率方法，对扭转不平衡结构的非弹性地震反应进行了评估，以期建立更合理的设计方法。地震反应的知识，计算由归一化的真实和合成加速度集合定义的地震运动；用于在检查广泛的基于弹性的程序中获得物理洞察力，这些程序广泛用于抗震设计中扭转效应的现行规范。首先根据基于弹性的“静态”和模态叠加规则设计结构模型，然后对这些模型的非弹性响应进行显式评估，从而评估这些程序的有效性。如果超过地震反应参数（层间漂移或构件延性要求）的概率不超过相应的平衡（对称）系统的概率，则扭不平衡结构将被判断为设计合理。建立的标准将有助于识别当前实践中的缺陷，并将提供一种方法来测试和系统地修改不同的设计规则，直到获得令人满意的概率。该项目的结果为地震力引起的多层建筑扭转效应提供了至关重要的数据。

This research study is a joint collaborative research effort between an academic research unit and a professional design office to investigate seismic torsional effects in multistory buildings. Two projects (BCS 9020394 and BCS 9116089) are combined into a joint cooperative study of the referenced topic area as a single research effort. By means of analytical models and a probabilistic approach, this research study evaluates the inelastic seismic response of torsionally unbalanced structures, with a view towards developing more rational methods of design. Knowledge of the seismic response, calculated for seismic motions defined by ensembles of normalized real and synthetic accelerograms, are used to gain physical insight in the examination of a wide range of elastically-based procedures widely used in current codes for torsional effects in seismic design. The validity of these procedures are assessed by first designing the structural models according to the elastically-based "static" and modal superposition rules, followed by an explicit evaluation of the inelastic response of these models. A torsionally unbalanced structure will be judged to have been properly designed if the probability of exceedance of a seismic response parameter (story drift or component ductility demand) does not exceed that for the corresponding balanced (symmetric) system. Criterion established will help identify deficiencies in current practice and will provide a method for testing and modifying systematically different design rules until satisfactory probabilities are obtained. Results from this project provide critically important data on the torsional effects in multistory buildings induced by seismic forces.