基于稳态简谐激励的人行桥模态参数识别  

Modal Parameters Identification of Footbridges Based on Steady-state Sinusoidal Excitations

作　　者：温青[1] 华旭刚[1] 陈政清[1] 王文熙[1] 牛华伟[1] WEN Qing HUA Xu-gang CHEN Zheng-qing WANG Wen-xi NIU Hua-wei(Key Laboratory for Wind and Bridge Engineering of Hunan Province, Hunan University, Changsha 410082, Hunan, China)

机构地区：[1]湖南大学风工程与桥梁工程湖南省重点实验室,湖南长沙410082

出　　处：《中国公路学报》2017年第2期98-106,共9页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(51278189);国家自然科学基金重大研究计划项目(91215302);国家优秀青年基金项目(51422806)

摘　　要：为了探究稳态激振现场试验方法在人行桥模态参数识别中的可行性,通过数值仿真分析和现场试验,研究了基于稳态激振的人行桥模态参数识别。该方法首先通过单点简谐激励获得结构稳态响应的频响函数(FRF),然后对实测频响函数按单模态或多模态叠加形式进行最小二乘曲线拟合得到结构的固有频率、阻尼比、模态振型和模态质量。以一频率密集分布的多点弹性支撑梁为数值算例,分析了激振器激振质量、频率间隔、激振次数、多模态参与和噪声对识别结果的影响。采用该方法识别了一座双层分离桥面曲线人行桥第1阶侧弯模态的频率、模态质量及阻尼比,为该桥的人致振动分析及减振设计提供了有效手段。结果表明:激振质量会改变结构固有模态参数,因此在满足激振条件下激振质量应尽可能小;选择合适的激振带宽和较小的激振频率间隔能获得更可靠的结果;人行桥现场稳态激振试验识别的频率和阻尼比与自由振动识别结果基本相符,识别的模态质量与有限元计算结果相符,说明该方法可行。To investigate the feasibility of field steady-state forced vibration test on modal parameters identification of footbridges,modal parameters identification of footbridges based on steady-state forced vibration was investigated by numerical simulation analysis and field tests.Firstly,frequency response functions（FRFs）of the steady-state structural responses based on sinusoidal excitation were obtained.Then,the measured FRFs were employed to estimate inherent frequency,damping ratio,modal shape,modal mass by least squares curve fitting methods in form of either a single-mode FRFs or a multi-modes FRFs.Numerical simulations of a elastically multi-supported beam with closely spaced frequency were carried out to analyze the effects of additional mass of exciter,frequency step,number of excitation,multi-mode vibration and noise on identification results.The natural frequency,modal mass and damping ratio for the first lateral mode of a double-level cable-stayed bridge with separate deck systems for pedestriansand vehicles were identified,which provided effective means for the analysis of pedestrian-induced vibration and the design of vibration reduction.The results show that inherent modal parameters of the structure can be changed by the exciter mass,so the exciter mass should be as small as possible under the conditions of sinusoidal forced vibrations. Choosing suitable exciting bandwidth and small vibration frequency step is important to obtain modal parameters accurately.The frequency and damping ratio of footbridge estimated by field steady-state forced vibration tests are in accordance with the results estimated by free vibration tests,and the identified modal mass is identical to the result by finite element model（FEM）,which demonstrates that this method is reliable.

关 键 词：桥梁工程 人行桥 模态参数识别 强迫振动试验 频响函数 模态质量 

分 类 号：U441.3[建筑科学—桥梁与隧道工程]