城市轨道交通箱梁中高频振动导纳特性试验研究

Study on Mid-and High-frequency Mobility Characteristics of Urban Rail Transit Box-girders

以某城市轨道交通30 m混凝土简支箱梁为研究对象,开展现场锤击试验,对其中高频振动导纳特性进行了研究。结果表明:简支箱梁顶板和翼板导纳优势频段为中心频率80 Hz^125 Hz,峰值频率为100 Hz;腹板和底板导纳优势频段为中心频率63 Hz^100 Hz,峰值频率为80 Hz。随着距离激励点距离的增大,箱梁各板件的中高频振动导纳逐渐减小,作用在箱梁上的力对距离激励点L/4(L为桥梁跨度)以外的梁段影响很小。简支箱梁各截面的形式沿纵桥向变化不大,因而各截面的中高频振动特性也差别不大。箱梁各板件导纳峰值频率重合可能引起板件共振,增大板件振动和噪声辐射。增大简支箱梁各板件厚度能够抑制其中高频振动,有利于减振降噪。

A hammer excitation test was carried out on a 30 m long simply-supported box-girder of an urban rail transit line, and the mid-and high-frequency mobility characteristics were investigated. The results show that the predominant frequencies of top slab and flange slab mobility are both ranged from 80 Hz to 125 Hz with peak value central frequency of100 Hz; while the predominant frequencies of web slab and bottom slab mobility are both ranged from 63 Hz to 100 Hz with peak value central frequency of 80 Hz. Mid-and high-frequency mobility of each slab decreases gradually with the increasing of the distance between the testing location and the excitation location. The force acting on the box-girder has little effect on the beam segment beyond L/4（L denotes the box-girder span） from the excitation point. The mid-and highfrequency vibration characteristics of the cross sections of the box-girder are almost the same due to their similar shape and size. The coincidence of the peak frequencies of the slab mobility may cause the resonance and amplify the vibration and noise radiation. Increasing the thickness of each slab can restrain the mid-and high-frequency vibration and is beneficial to the vibration and noise reduction.