Fundamental study on failsafe structural systems against large earthquakes using uplift mechanism

本研究旨在探讨一种采用扬起机制的失效安全结构体系的可能性和有效性，以使建筑物即使在比按常规抗震设计规范估计的地震反应效应更大的情况下也能保持安全。前人的研究表明，伴随着隆起运动的摇摆振动可以减少建筑物在强烈地震作用下的震害。提议的FAT-1-1。系统就是基于这一知识。该体系在一定的地震输入水平下表现出固定柱基体系的地震反应特征，但一旦地震输入水平超过限值就开始摇摆。首先，为了将扬起机理引入到建筑结构中，研究了以下几个方面的内容：1)利用扬起机制的钢框架体系；2)柱脚的恢复力特性，使钢框架扬起；第二，为了建立更适合于摇摆结构的抗震性能评价方法，开展了以下研究项目：3)摇摆结构的地震侧向力分布；4)地震时楼板倾斜对摇摆结构中室内物体的影响。基于简化建筑结构模型的地震反应分析，对以下研究项目进行了研究。5)提出了基于扬起机制的失效安全体系对强烈地震作用的有效性。通过这些研究，提出了摇摆结构的框架体系和结构构件，并对其上拔响应特性进行了定量的分析。并验证了所提出的故障保险系统对强震的有效性。将该体系应用于高宽比建筑时，其抗震性能几乎可与滞回阻尼器被动控制体系相媲美。

This study aims to investigate possibility and efficiency of a failsafe structural system using uplift mechanism to make buildings safety even against larger earthquake response effects than those estimated with ordinal seismic design codes. Previous studies have cleared that rocking vibration accompanied with uplift motion might reduce the seismic damage of buildings subjected sever earthquake motions. The proposed fat-1mi. system is based on this knowledge. This system shows seismic response characteristics of a fixed column base system under certain seismic input leveL But it starts rocking once the seismic input level exceeds the limit. Uplift response due to the rocking will restrain ascent of seismic input to the structures.Firstly, to introduce uplift mechanism to building structures, the following research items were studied.1) Steel frame systems utilizing uplift mechanism2) Restoring force characteristics of column bases to make steel frames upliftSecondary, to develop more appropriate seismic performance evaluation methods for rocking structures, the following research items were studied.3) Seismic lateral force distribution of rocking structures4) Effect of floor incline during an earthquake to indoor objects in rocking structures Finally, the following research item was studied based on earthquake response analyses using simplified building structural models.5) Efficiency of the proposed failsafe system using uplift mechanism against sever earthquake ground motionsThrough these studies, some frame systems and structural members for rocking structures were proposed and uplift response characteristics were analyzed quantitatively. And the efficiency of the proposed failsafe system against sever earthquakes was confirmed. When we apply this system to buildings with a high aspect ratio, it can provide them superior seismic performance, which is almost equal to that of passive vibration control systems with hysteresis dampers.