Abstract:
Abstract: The key point to analyze dynamic characteristic of aqueduct is the coupling effect caused by the interaction between water and aqueduct. In order to simulate the coupling effect effectively and improve the accuracy of working modal characteristics, Jingdian project in Gansu (103.45-104.04o E, 37.26-37.36oN) was selected as the research object. Added masses model and fluid solid interaction (FSI) system coupling model were built under different forms of water coupling. First, different coupling models were calculated and analyzed under the conditions of different water levels by using different modal extraction methods based on different solving principles,obtaining graphics of principal frequency and vibration shapes of aqueduct structure. Then the same span aqueduct was tested to get the dynamic displacement response under operational excitation conditions, and the tested response signals were de-noised by wavelet threshold and empirical mode decomposition (EMD) to extract effective vibration information. Thus the structural natural frequency could be identified by hilbert-huang transform (HHT) modal parameter identification method. Finally, the modal frequency in normal water level condition of added mass model and the FSI system coupling model was compared with frequency measured by HHT method. The results showed that the calculation results of different coupling models had a certain degree of decline compared with the results under the anhydrous condition, and the largest amplitude of fundamental frequency was 15.03%. So the interaction of water and aqueduct had a greater impact on natural frequency of aqueduct structure and could not be ignored in structural dynamic characteristics analysis. The frequency error percentage between added mass coupling modal calculation results and identification results was 3.23%-10.56%, while the simulation results of the FSI system coupling model suited well with the HHT identification results, and the effective frequency error ranged from 0.18% to 4.59%. The maximum frequency error of FSI system coupling model was 5.97% smaller than the added masses model. What's more, the frequency error of same order was smaller than the added massed model, and it could offset the modal lack of the added massed model. The comparison results of finite element simulation and modal identification showed that the HHT modal identification method was able to extract the modal parameters of the aqueduct, which had high identification precision. Coupling model of FSI system considering the coupling effect of solid-liquid was superior to added masses model in simulation order and precision and could reflect the real characteristics of aqueduct more comprehensively and accurately. Meanwhile, the FSI system coupling model could be applied in the dynamic characteristics analysis of other kinds of aqueduct and could also provide guidance for the selection of dynamic model while evaluating health condition of aqueduct structure.