论文部分内容阅读
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。
In order to investigate the feasibility of the steady-state excitation field test method in modal parameters identification of footbridge, modal parameters identification of footbridge based on steady-state excitation is studied through numerical simulation and field experiments. In this method, the frequency response function (FRF) of the steady-state response of the structure is first obtained by a single point harmonic excitation, and then the natural frequency of the structure is obtained by fitting the measured frequency response function by the least square curve according to the single modality or the multi-modal superposition form , Damping ratio, mode shape and modal mass. The frequency-intensive multi-point elastic support beam is used as a numerical example to analyze the influence of exciter vibration quality, frequency spacing, excitation frequency, multi-modal participation and noise on the identification results. The method is used to identify the frequency, modal mass and damping ratio of the first-order bending mode of a double-decker bridge deck curve footbridge, which provides an effective method for vibration-induced vibration analysis and damping design of the bridge. The results show that the excitation quality can change the intrinsic mode parameters of the structure. Therefore, the excitation quality should be as small as possible when the excitation is satisfied. More reliable results can be obtained by selecting the appropriate excitation bandwidth and the smaller excitation frequency interval. The identification frequency and damping ratio of the steady-state excitation test in footbridge basically coincide with the results of free vibration identification, and the identified modal quality is consistent with the finite element calculation results, which shows that the method is feasible.