BEHAVIOR OF NONSTRUCTURAL COMPONENT SUPPORTED BY HANGER BOLTS UNDER SEISMIC EXCITATIONS BY SHAKING TABLE TEST

During the Great East Japan Earthquake of March 2011, nonstructural components, such as pipe systems, ducts, cable racks and ceilings were severely damaged while main structural members in the building were not damaged seriously. Pipes, cable racks, apparatus and ducts' hanger bolts were ruptured causing the equipment to fall down. Because of these damages, buildings cannot be used for a long period of time and one person was killed by pipe's falling in Japan. In this study, the behaviors of nonstructural components are investigated by conducting shaking table tests to verify the cause of damage. More specifically, damage to hanger bolts is investigated by simulating its rupturing mechanism through shaking table test. To simulate the real installation condition of nonstructural components, apparatus-duct-pipe system supported by hanger bolts is selected as specimen. Roof floor response wave at the actual 5-story steel building under the Great East Japan Earthquake and sweep wave are used for the input waves. The maximum response acceleration was about 4 G in X direction under response wave 75% and the damage occurred at the metal fitting which is the connection part between braces and hanger bolt. And without installing braces, the upper hanger bolts at the fixed supporting part were ruptured easily since the natural frequency of the specimen closed to those of target building during excitations and the response became huge.

2011年3月东日本大地震期间，建筑内的非结构构件（nonstructural components）如管道系统、风管、电缆桥架及吊顶遭受严重损坏，而建筑主体结构构件并未受到明显损伤。管道、电缆桥架、设备及风管的吊杆螺栓发生断裂，导致设备坠落。此类损坏使得建筑长期无法投入使用，日本曾发生因管道坠落致人死亡的事故。本研究通过开展振动台试验（shaking table tests）探究非结构构件的受力行为，以验证其损坏成因；具体而言，通过振动台试验模拟吊杆螺栓的断裂机理，对其损坏情况展开研究。为还原非结构构件的实际安装工况，本研究选取由吊杆螺栓支撑的设备-风管-管道系统作为试验试件。试验输入波采用东日本大地震中某实际5层钢结构建筑的楼层顶板响应波与扫频波（sweep wave）。在75%幅值的该响应波作用下，X方向最大响应加速度约为4G，试件在支撑斜杆与吊杆螺栓的连接部位的金属连接件处发生损坏。当未安装支撑斜杆时，由于试验过程中试件的固有频率与目标建筑的固有频率相近，导致响应幅值大幅增大，固定支撑部位的上部吊杆螺栓极易发生断裂。