Abstract：The operational mode is an important parameter for describing the dynamic characteristics of practical structures. Based on the basic theory of structural dynamics, the essence of the dynamic mutual feedback mechanism between the vibration testing and the modal identification is explained. The primary reason for the low accuracy of traditional modal testing is the separation of the vibration testing and the modal identification. The concept of dynamic coordination, with the vibration testing serving the modal identification in a forward way and the modal identification guiding the vibration testing in a backward way, is put forward. Following that, the intercoordination theory of testing and identification for obtaining structural operational modes is established. Furthermore, the theoretical framework consisting of the criteria of the response strength, the identification error and the reconstruction accuracy is developed. Based on the simulation data of a structural health monitoring benchmark model and the field measured data of a long-span bridge, it is concluded that the intercoordination theory can effectively solve the blindness of the vibration test and the passiveness of the modal identification. At the end, the future work of the intercoordination theory for structural operational modes was summarized.
