Effects of Hardening and Deteriorating Properties of Members on Collapse Behavior of Building Structures

本课题的目的是明确框架结构的倒塌行为，为防止框架结构在强震作用下倒塌提供设计依据。本课题取得了以下成果：(1)对每层都有质量的较为真实的框架模型进行了精确的动力响应分析。结果表明，动力坍塌过程中存在变形集中现象，主要表现为弓形偏转模式的增长，并集中在下部受限区域。并提出了变形集中区高度的预测方法。(2)对由劣化构件组成的多层弱梁平面框架结构在强震作用下的倒塌行为进行了研究。结果表明，用e-…可以预测变形集中区的高度。在以前的研究中发展了更广泛的方法版本(1)。通过数值响应分析验证了该方法的有效性。通过对几种不同负刚度框架达到最大强度后的倒塌行为的研究，阐明了构件的劣化对动力倒塌行为的影响。(3)提出了防止多层框架在强震作用下特定振型挠度加速增长时发生严重倒塌的新准则。提出了抑制摇摆漂移的判据，以满足更高级别的安全要求。(4)通过对弱梁式框架模型的振动台试验研究，揭示了弓形振型增长现象的存在及其特征。对钢框架进行了地震反应分析，考虑了地震作用下梁端脆性断裂的影响。并与延性框架的反应特性进行了比较，讨论了断裂对钢框架地震反应的影响。较少

The purpose of this project is to clarify the collapse behavior of building frames and to develop the design criteria for preventing the frames from falling into collapse under strong earthquake. The following results have been obtained in this project.(1) Accurate dynamic response analyzes have been carried out for more realistic frame models which have a mass at every floor. It has been revealed that there exists deformation concentration phenomena in the process of dynamic collapse, which is characterized by the growth of bow-shaped deflection mode and the concentration of this mode in the restricted lower region. And the method have been proposed for predicting the height of the deformation concentration region.(2) An unknown type of collapse behavior have been revealed for multistory weak-beam planar frames which consists of deteriorating members and subjected to a severe earthquake. It has been shown that the height of the deformation concentration region can be predicted by an e … More xtended version of the method developed in previous studies (1). The validity of the method is verfied through numerical response analyzes. The effects of the deteriorating properties of members on the dynamic collapse behavior are then clarified by investigating the collapse behaviors of several frames wiht different negative stiffnesses after reaching the maximum strengths.(3) New criteria for preventing multistroy frames from severe collapse with an accelerative growth of the particular mode deflection during strong earthquake ground motion has been proposed. Criteria for suppressing the sway drift has also been proposed to meet higher-level safety requirements.(4) Existence of growth phenomena of the bow-shaped mode and its characteristics have been revealed by experimental study using shaking table for weak-beam-type frame models. The drift of the sway-mode vibration center has also been clarified.(5) Seismic response analyzes, considering the effects of brittle fractures at beam-ends during an earthquake excitation, have been carried out for steel frames. The response properties have been compared to those of ductile frames and the effects of fractures on the seismic response of steel frames are discussed. Less