东莞市东江大桥在国内首次采用三桁刚性悬索加劲钢桁梁新型结构，为了获得该复杂结构的模态参数和确定成桥理论计算模型，基于环境激励法，在通车前对该桥进行了模态试验，然后采用频域识别法，获得了该复杂结构的竖向、横向和扭转等模态参数．通过对比试验结果与三维有限元计算结果得出: 三桁结构整体受力性能较好; 预制栓接桥面板对整体刚度的贡献不可忽略; 梁板全刚性连接模型更符合大桥整体节点连接结构，其所计算的自振模态与相应实测结果总体上吻合较好，且理论振动频率均比实测值稍小，前4 阶的频率差在4%以内，这主要是对该桥整体节点刚度欠仔细考虑的缘故．

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%.