| Studies on vibration due to vehicle loads and seismic responses of bridges are two important contents of bridge dynamic analysis. On the one hand, in recent years, with the development of traffic cause, the traffic density, the load and the moving speed of heavy vehicles increase day by day. Meanwhile, bridges are tending towards longer, lighter and more flexible in order to adjust to the development of highway traffic and bridge construction. Therefore, the problem of vehicle-bridge coupled vibration has been attracting extensive attention. Study on the bridge vibration due to moving vehicles is helpful to improvement of bridge structural design, specification of vehicle loads, control of vehicle moving speed and decrease of bridge damage. On the other hand, the bridge is an important component of lifeline engineering, its power to resist disaster is especially important. The seismic study of bridge structures is recognized widely after much damage in previous earthquake. The earthquake damage of some bridges designed according to seismic code is still serious. Therefore, it indicates that the seismic design theory and method of bridge used in the present are also insufficiency, especially for the bridges with special structure. In the calculation of seismic response of bridge, considering soil-structure interaction, bridge overall seismic analysis method through building the overall model of pile-soil-bridge is essential. Therefore, based on Sanhao Bridge (cable-stayed bridge with steel arch tower) in Shenyang City, the vibration induced by vehicle and seismic response of such new type cable-stayed bridge were studied in this thesis.Firstly, field dynamic test of cable-stayed bridge with steel arch tower was executed. In the test, the cable forces of completed stage, natural vibration characteristics and forced vibration responses of cable-stayed bridge were measured. The testing data can provide basic data and check instrument for numerical analysis.The planar vehicle model and spatial vehicle model were built, and the dynamic equilibrium equations and vehicle-bridge coupled interaction forces of vehicle models were derived. The samples of road roughness used to numerical analysis of bridge vibration induced by vehicles were generated by trigonometric series superposition method. Iterative method was used to solve the problem of bridge vibration due to moving vehicles, and the calculation program of bridge vibration induced by vehicle was compiled.The global vibration due to moving vehicle of cable-stayed bridge with steel arch tower was researched using numerical simulation method. Main girder and arch tower were simulated using spatial beam elements and inclined cable and horizontal cable were simulated using spatial bar elements. Planar model of three-axle vehicle was used. The effects of road roughness, vehicle velocity, bridge damping and vehicle suspension stiffness on bridge global responses due to vehicle loads were analyzed. Furthermore, the bridge responses induced by moving forces and vehicle model were compared.The local vibration due to moving vehicle of cable-stayed bridge with steel arch tower was also studied numerically. Box girder and arch tower were simulated using shell elements and inclined and horizontal cables were simulated using spatial bar elements. Spatial model of three-axle vehicle was used. The accuracy and applicability of numerical calculation were checked through comparing numerical results and dynamic test results of local vibration due to vehicle loads of cable-stayed bridge. Furthermore, the effects of road roughness, vehicle velocity, bridge damping and vehicle suspension stiffness on bridge local responses were also analyzed. Meanwhile, differences between global dynamic amplification factors and local dynamic amplification factors of responses of cable-stayed bridge induced by vehicle were compared.Normal seismic responses of cable-stayed bridge with new tower structure were analyzed. The three-dimensional finite element model of bridge suitable for seismic analysis was built. Then the natural vibration characteristics and seismic responses using response spectrum method of the model were studied. Furthermore, the seismic responses of cable-stayed bridge were studied by time history analysis using El-Centro wave, Qian’an wave and two artificial waves. In the same time, the results of seismic responses of cable-stayed bridge of response spectrum analysis and time history analysis were compared.The viscoelastic artificial boundary with higher calculation accuracy was used to treat wave motion problem of external source of infinite domain and was carried out in finite element software ANSYS. The wave propagation effect in infinite domain was translated to equivalent loads on viscoelastic artificial boundary using local decomposition technique of wave field. Meanwhile, the equivalent load expression of seismic wave input was given under vertical incidence of planar seismic wave. Moreover, an example was calculated to check the validity of input method of planar seismic wave under vertical incidence in this thesis.In the last, the three-dimensional finite element model of pile-soil-bridge of cable-stayed bridge with steel arch tower was built. Then the seismic responses of cable-stayed bridge was studied numerically using global approach in the cases of P wave, S wave (longitudinal vibration) and S wave (lateral vibration) under vertical incidence, respectively. Furthermore, the results of seismic responses between global approach and not considering soil-structure interaction effect were compared.The research results in this thesis possess theoretical guidance meaning and practical application value for structural design and safety of transport operation of cable-stayed bridge with steel arch tower. Although this thesis was based on cable-stayed bridge with steel arch tower, the analysis methods of bridge vibration due to vehicles and seismic responses considering soil-structure dynamic interaction are also suitable for other bridges. |
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