基于环境振动的某设置防震缝结构的动力特性

Dynamic Characteristics of a Building with Seismic Joints Based on Ambient Vibration

对于设置防震缝的既有相邻结构,防震缝的塞缝和盖缝处理措施可能引起相邻结构间的动力相互作用,由此引起的模态会增加模态参数识别的复杂程度.以利用悬臂构件形成防震缝的某钢筋混凝土办公楼为例,该办公楼由主楼、东楼和西楼三部分组成,在各相邻结构内分别进行环境振动测试,利用频域分解法对其模态参数进行识别,得到了主楼和东楼的四阶及西楼的两阶自振频率、阻尼比和振型.由于各相邻结构间存在因防震缝的填缝措施引起的相互作用,导致一个结构的自振频率和由相互作用产生的频率混杂在一起.各结构有限元模型的自振频率和振型与识别结果吻合较好,但由于结构间的相互作用增强了整栋建筑的整体性,主楼和东楼的有限元模型的第三阶扭转频率均小于识别结果.对设置防震缝的相邻结构来说不应总是假定相互之间是独立的.

Technical solutions for sealing and covering seismic joints may induce dynamic interactions between as-built adjacent structures. Moreover, noise modes due to dynamic interactions make modal parameter identification complex. In this paper, ambient vibration tests were conducted to obtain the actual dynamic characteristics of a reinforced concrete office building, whose seismic joints were formed by cantilever members. The tested building was divided into the main building, eastern building and western building. Tests were conducted in each structural part separately. Four modes of the main building and eastern building, and two modes of the western building were identified using the frequency domain decomposition method. The results show that due to the dynamic interactions between adjacent structures caused by the infill of the seismic joints, natural frequencies of a structure were mixed together with those due to the interactions with the adjacent structures. Modes of each building from the finite element models agreed well with the identification results, except that the third natural frequencies of the main building and eastern building were smaller than the identified ones, because the integrity of the whole building was enhanced by the dynamic interactions. Therefore, it should not always be assumed that adjacent structures with seismic joint are independent.