基于脉动法的大型单立柱两面体广告牌结构模态测试与数值分析

Modal Testing and Numerical Analysis of Large Double-sided Monopole Billboard Based on Impulse Response Method

基于脉动法对大型单立柱两面体广告牌结构进行了动力特性现场测试,获得了其前三阶频率、振型和阻尼比。针对实测结构,利用SAP2000软件建立了考虑和未考虑牌面围护结构刚度的两种结构有限元模型,获得了结构自振的计算频率和振型。对比结构实测和数值计算结果表明:考虑牌面围护结构刚度的数值计算频率与实测频率基本一致,建议进行广告牌结构动力特性分析时应考虑牌面围护结构刚度的影响;实测振型与数值计算振型基本一致;实测阻尼比比规范规定的阻尼比大70%以上,今后在设计时可以适当提高单立柱两面体广告牌结构阻尼比。

In this paper,the dynamic characteristics of a large double-sided monopole billboard structure were field tested based on the impulse response method,and the first three-order frequencies,mode shapes and damping ratios were obtained.For this specific structure,two structural finite element models,with and without the enclosure stiffness,were established by using SAP2000 software,and their frequency and mode shapes were obtained.The field measured data and numerical results were than compared.The calculated numerical frequency considering the enclosure stiffness is generally close to the measured one.Thus,it is suggested that the influence of the enclosure stiffness should be considered when analyzing the dynamic characteristics of the monopole billboard structure.The measured mode shapes are consistent with the calculated ones.The measured damping ratio is more than 70% higher than the value specified in the code.Thus,the damping ratio of double-sided billboard monopole structure can be appropriately increased in the future design.