Papers by Author: Zhe Zhang

Abstract: The separation between the filled-concrete and the steel tube would reduce tremendously the bearing capacity of the concrete-filled steel tubular (CFST) arch bridge. However, there is no efficient method to monitor and detect the separation so far, which is a great engineering problem we have to solve. Therefore, this paper firstly proposes a vibration test method aiming at the local modal of the steel tube. Distributed accelerometer array deployed along the tube is used to acquire the vibration signal induced by quantitative excitation via telecontrol. Changes in frequency and amplitude of the steel tube are selected as parameters for the separation detection based on the theory of surface wave transmission. This method can satisfy the demand of the real-time monitoring of interface separation of the CFST arch bridge.

Abstract: Hangers are the critical elements supporting stiffening girder in suspension bridge. The hangers probably break suddenly in service for the reasons of corrosion, fatigue or traffic accident. Because the hangers are anchored to the main cable, the sudden breakage of hanger causes strong vibration of main cable, and the vibration may damage some of the elements of the bridge. Using nonlinear dynamic analysis methods and adopting 3D finite element model, the responses of a suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of hanger has significant effects on tensions of the hangers adjacent to the broken hanger, the maximum tension of hanger produced by breakage of a hanger exceeds 2.2 times of its initial value, and the tensions of other hangers far away from the broken hanger are affected little. The breakage of a single hanger causes very large torsion moments of girder and reactions of bearings, but it has little effects on the tensions of main cable and moments of tower.

Abstract: The results of unsteady Reynolds averaged Navier-Stokes (URANS) simulations of flow around a square cylinder using two-dimensional hybrid meshes were presented in this paper. The first part examined the accuracy of various RANS turbulence models, i.e. the standard model, RNG model, realizable model, standard model, SST model, and RSM, by comparing their results with available experimental data. Despite the limits imposed by the RANS approach and the relatively inexpensive two-dimensional computations, the main features of this complex flow can be predicted reasonably well. Among the computations using various RANS models compared here, the SST model shows the best agreement with the experiment. The second part investigated the effects of corner cutoffs on unsteady flow characteristics around a square cylinder by using the SST model. Especially the detailed near-surface flow structure around the cylinder was focused on, aiming at giving an explanation for the drastic modification of the aerodynamic characteristics as the corner shape is slightly changed.

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: The paper studye the effect of shrinkage and creep on the cable-stayed suapension bridge. In order to research the static action of cable-stayed suspension bridge, two plane models of Jinzhou Bay Bridge is analyzed under shrinkage and creep by using general FEM software. One is a self-anchored bridge and the other is an earth-anchored bridge. The differences in static behavior between the two bridges are compared in detail. The results indicated that the shrinkage and creep effects have great influences on both bridges, and the effects have greater influences on self-anchored system than earth-anchored system. In addition, the author analyzes the causes of these differences between the two bridges. In conclusion，shrinkage and creep have some effect on the bridge displacements and internal forces. It is an important factor which can not be ignored in the design.

Abstract: Tong-Tai Bridge is a special-shape arch bridge with arch obliquely cross the curved beam. In order to validate the theoretical solutions and ensure the structure safety, model test is discussed. In this paper, the structural design, fabrication procedures and test method of the model are presented. Meanwhile, the finite element method is applied to analyses this special structure. Some experience of the structure construction is obtained during the practice process and the experimental results achieved are satisfactory.

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: This paper introduces a new box girder widening method- Steel cantilever widening concrete box girder method without piers (SCWCGM for short). Without additional piers, SCWCGM can still meet the need of widening range, which is an effective widening method for urban bridges. In this paper, the widening conception and the structure style of SCWCGM is detailed. In order to study the mechanical properties of this method, the full-scale model test was conducted. The results show that, the SCWCGM is reasonable and feasible.

Abstract: Because the traditional pushover analysis can not take the contributions of higher modes into account, To overcome this limitation, a modal pushover analysis procedure (MPA) is proposed by some researchers, which can involve the combination of multi-mode contributions to response. In this paper, much improvement on MPA procedure is made with consideration of the changes of seismic response after structural yielding and anew distribution of inertia forces. The method is verified by one example of bridge structure. It is concluded that the improvement part-sectionalized MPA presented in this paper has high accuracy.

Abstract: The method of strengthening the existing reinforced concrete suspension bridges by changing suspension system into cable – stayed- suspension system is presented in this paper. Based on a typical bridge, the analysis of the static behavior of the bridge before and after the strengthening is preformed. The results show that the bending moment of the girder is reduced obviously and the capacity of carrying load is greatly improved. The original cable system is fully utilized and can meet force requirement. It has certain theory significance and practical engineering value to the similar bridge’s strengthening.