Papers by Author: Fu You Xu

Abstract: The basic concepts and theories of Hilbert-Huang-Transformation (HHT) for signal analysis is introduced and its implementation procedure is programmed. For the collected three orthogonal directions wind speed signals at a measuring point at Sutong Bridge site, Empirical Mode Decomposition (EMD) is conducted to extract the Intrinsic Mode Functions (IMFs). Hilbert transformation is performed on IMFs and its marginal amplitude spectra and amplitude spectra are achieved. The orthogonal exponential matrix that reflects the orthogonalities between the IMFs is obtained, and eigenvalue decomposition is carried out. The results show that the measured wind speed appears non-stationary nature, even for the same measuring point, for the wind speed at different directions, the dominant frequencies are distinct.

Abstract: Active Mass Damper has been proven to be efficient in suppressing structure vibration. Previous studies of AMD have been concentrated on the vibration control of buildings under earthquake excitation, whereas few investigation of wind-induced bridge vibration control has been conducted. In consideration of the characteristics of one suspension pipeline bridge which behaves dramatic lateral and torsional response under fluctuating wind action, a two-DOFs TMD/AMD system for suppressing both lateral and torsional responses was proposed. The bridge is modeled using Ansys and the buffeting responses of the bridge under TMD, AMD control are respectively simulated and analyzed by MATLAB/Simulink. The efficiency of different control system has been studied. The results show that two-DOFs AMD system has a better performance in suppressing the buffeting response of lateral bending and torsion. In addition, AMD system can be applicable to a wider range of frequency and therefore manifests the more stable performance than TMD under fluctuating wind loads which contain various frequency components.

Abstract: By using FEM method, the natural frequencies of the super-long steel and CFRP cables with possible engineering parameters have been comprehensively studied. The error and limitations of cables’ natural frequencies theoretical calculation formula have also been analyzed. The results show that: Theoretical formula results are more approximate to out-plane frequencies of the cables. In a symmetric mode, out-plane frequency is lower than in-plane frequency, whereas in an asymmetric mode the situation is reversed. The difference between out and in-plane frequencies appear most in the first-order mode. The difference between out and in-plane frequencies is more obvious for cables with low stress, small inclined angle, long length with big sag and strong nonlinearities. The nonlinearities of CFRP cable is relatively slight for its lightweight and high strength. Out and in-plane frequencies are almost identical, and the theoretical formula is applicable to CFRP cables.

Abstract: A comprehensive study of force measurement test in wind tunnel is conducted for the streamlined deck model of Dalian Cross-sea Bridge scheme. The factors, including stacking load in erection, vehicles arrangement, central slot and so on, are analyzed in terms of the influence of the three-component coefficient in the way of microscopic mechanism. The stall angles under different working conditions are also investigated. The results show that stacking loads and vehicle arrangement barely have any impact on the three-component coefficient, which can be neglected approximately; lift and pitching coefficients decrease for the slotted deck, and the slot width has little influence on the aerostatic coefficients; bridge railing, stacking loads and vehicles change the flow separation and re-attachment around the deck, increasing the turbulence intensity, leading to the fluctuation of stall angles.

Abstract: Study on wind-resistant performance of one special-shaped long-span arch bridge is carried out using a full-bridge aeroelastic model with a scale of 1:66 in wind tunnel test. The tests on vortex-induced vibration (VIV for short), buffeting and aerodynamic stability of both bare arch and full-bridge are comprehensively conducted in smooth and turbulent flows with attack angle of -3º, 0º, 3º, and yaw angles ranging from 0º to 180º with a step of 15º. The results show that the first-order symmetric VIV of vertical bending appears on the bare arch in smooth flow with attack angle of -3º, 0º, 3º, and yaw angle of 0º, 5º. The maximum amplitude of VIV at 1/4 section of the bare arch is close to 30cm, higher than the corresponding value at the crown section. No stable VIV is observed on full-bridge model tests in both smooth and turbulent flows. For full-bridge model in turbulent flows, both means and standard deviations of girder torsional displacement at 1/2 and 1/4 sections are very small, which prove that the bridge integral torsional stiffness is significantly improved due to the 3-D cable-support system. The bridge possesses good aerodynamic stability for both bare arch and full-bridge service states.