关键词: 模态参数, 双层公路桥, 环境激励, 刚性悬索

Abstract:

Dongjiang Bridge is the first double-deck and three-main-truss steel bridge stiffened with rigid suspension in China. In order to determine the modal parameters and obtain a theoretical model of the whole bridge,a modal test based on ambient excitation was carried out before the open to traffic. Then,the vertical,horizontal and torsional modal parameters of the bridge were obtained by means of the frequency-domain identification method. Finally,a comparison was performed between the test results and the results calculated by the 3D finite element method. It is indicated that ( 1) the three-main-truss steel bridge is of strong integral bearing capacity; ( 2) the contribution of the precast bolting deck to the integral stiffness of the bridge is non-neglectable; ( 3) the model with rigid beamplate connections well describes the joint connection of the whole bridge,and the corresponding calculated intrinsic vibration mode accords well with the tested ones; and ( 4) due to the deficiency in considering the integral joint stiffness of the bridge,the theoretical vibration frequencies are slightly lower than the tested ones,with a first fourorder frequency difference being less than 4%.

Key words: modal parameter, double-deck highway bridge, ambient excitation, rigid suspension