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

对结构在过去地震中的性能观察表明，平面不对称的建筑往往遭受更大的破坏，因为要避免平面上刚度和强度分布不规则的建筑是不现实的，而且这类建筑特别容易受到地震破坏，因此迫切需要对这些建筑的地震反应有更好的了解。这项研究项目的目标是：(1)更好地了解建筑物在地震期间发生扭转运动时的非弹性反应；(11)开发适用于此类新建筑物的初步设计和现有建筑物的改造方案设计的简化分析程序；以及(3)建议--供SEAOC地震委员会等编写代码的实体审议--改进意外扭转和自然扭转的规范规定。这项研究的主要特点是利用仪器齐全的建筑物在最近地震期间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影响估计。所开发的全面但简单的分析和设计应该对该专业有直接的好处。它们将有助于检查新建筑的初步设计，评估对现有建筑进行翻新的替代方案，这些建筑的图则不对称程度高得令人无法接受，并有助于改进建筑法规。

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.