Accidental and Natural Torsion in Earthquake Analysis, Design and Retrofit of Buildings

对以往地震中结构性能的观察表明，平面不对称的建筑物往往遭受更大的破坏，因为避免平面刚度和强度分布不规则的建筑物是不切实际的，这类建筑物特别容易受到地震的破坏，迫切需要提高对这类建筑物地震反应的认识。本研究项目的目标是：(1)提高对地震中建筑物遭受扭转运动的非弹性反应的理解；（11）制定简化的分析程序，适用于新建筑物的初步设计和现有建筑物的改造方案设计；（III）建议（供SEAOC地震学委员会等代码编写实体考虑）改进针对意外和自然扭转的代码条款。本研究的核心特征是利用仪器良好的建筑物在最近地震中的运动记录来评估和校准分析和设计程序，以确保这些程序提供可靠的扭转效应估计。所进行的全面而简单的分析和设计应该对行业有直接的好处。它们将有助于检查新建筑物的初步设计，评估对现有建筑物进行改造的替代方案，这些建筑物的平面图存在不可接受的大不对称，以及改进建筑规范。

Observations of performance of structures during past earthquakes demonstrate that buildings with asymmetric floor plan tend to suffer greater damage because it is impractical to avoid such buildings with irregular distribution of stiffness and strength in plan and such buildings are especially vulnerable to earthquake damage, there is urgent need to develop an improved understanding of the earthquake response of these buildings. The objectives of this research project are to: (1) develop an improved understanding of the inelastic response of buildings undergoing torsional motions during earthquakes; (11) develop simplified analysis procedures suitable for preliminary design of such new buildings and for the design of retrofit schemes for existing buildings; and (III) propose--for consideration by code-writing entities like the SEAOC Seismology Committee--improved code provisions for accidental and natural torsion. The central feature of the research is to utilize recorded motions of well instrumented buildings during recent earthquakes to evaluate and calibrate analysis and design procedures in order to ensure that these procedures provide reliable estimates of torsional effects. The comprehensive but simple analysis and design developed should be of direct benefit to the profession. They would be useful for checking the preliminary design of new buildings, for evaluating alternatives to retrofit existing buildings with unacceptably large asymmetry in their plans, and for improving building codes.