组合空腹板架结构自振特性研究

Research on free vibration characteristics of composite open-web floor structure

自振频率及对应的振型是结构的固有特性,也是承受动力荷载结构设计的重要参数。本文综合考虑钢—混凝土组合空腹板架结构的跨度、网格尺寸、构件尺寸等因素的影响,采用正交表L18(37),完成了在周边简支、周边固支、多点支承三类边界条件下的结构自振理论分析研究,得到了结构频率的变化规律及对应的振型分布规律。研究表明,影响结构自振特性的主要因素依次是跨度、剪力键高度和网格尺寸;在其他条件不变的情况下,周边固支比周边简支边界情况,结构基本频率平均提高80%,通过在跨中设置点支撑变为多跨结构,其自振频率大幅提高,接近于单跨对应的简支结构;结构自由振动以竖向振动形态为主,而当阶次较高(≥500)时,可能出现水平振动形态。另外,振型频率密集,变化集中在前9个振型,随振型阶次增加,频率增幅变小。

The frequency and the corresponding shape of free vibration are the structural natural characteristics and the important design parameters of structural subjected to dynamic loads.Considering span,grid size,component size and other factors of the steel-concrete composite open-web floor structure and adopting the orthogonal experimental design table L18（37）,this paper completes theoretical analysis of the structural free-vibration under three types of boundary conditions（simply support,fixed support,multi-point support）,and then obtains the change laws of the structural frequency and the corresponding mode shape.Research results are as follows：The main factors impacting the structural free-vibration characteristics are successively span,highness of shear key and grid size.In the event that the other conditions remain unchanged,compared with simple support boundary conditions,the structural fundamental frequency under fixed support improves 80% averagely.By setting point-support to form multi-span structure,the structural fundamental frequency under multi-point support increases largely,and comes close to the corresponding single-span simply-supported structure.The vertical vibration shape is the main form of the structural free vibration,and the level vibration shape may arise while higher order（≥500）.In addition,the modal frequency is fairly intensive,and the frequency change mainly focuses on the previous nine vibration modes（the higher the vibration mode order,the smaller the frequency change）.