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

过去地震中结构性能的观察表明，不对称平面的建筑物往往遭受更大的破坏，因为它是不切实际的，以避免这种建筑物的刚度和强度的不规则分布在平面上，这类建筑物是特别容易受到地震破坏，有迫切需要发展一个更好的了解这些建筑物的地震反应。 本研究项目的目标是：（1）提高对地震时建筑物扭转运动非弹性反应的认识;（11）开发适用于此类新建筑物初步设计和现有建筑物改造方案设计的简化分析程序;以及（III）建议--供诸如SEAOC地震学委员会之类的代码编写实体考虑--改进意外和自然扭转的代码规定。 这项研究的主要特点是利用最近地震期间记录的装有良好仪器的建筑物的运动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。 所发展的全面而简单的分析和设计应该对该行业有直接的好处。 它们将有助于检查新建筑物的初步设计，评估改造现有建筑物的替代方案，这些建筑物的计划中存在不可接受的大不对称性，并改进建筑法规。

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.