The Study On The Stability And The Vehicle-bridge Coupled Vibration Of High Pier And Long-span Continuous Rigid Frame Bridge

In recent years, with the west development of China, more and more continuous rigid frame bridge with big pier and long span have been built in the west. Along with the pier is increasing, the axis pressure of it is also increasing. Then the stability of the bridge structure and the vibration response under the influence of the vehicles and bridge are prominent.In this paper, the author has made an analysis of the stability of the bridge and the vehicle-bridge coupling vibration during and after its construction process on the basis of the previous researches. Based on the NO.3bridge in Huashan, the engineering background, the researches in this paper are as follows:1. The analytical calculating method is deduced with energy method for the autologous stability of naked pier and the cantilever during its construction phrase. Meanwhile, the concrete expression of the analytical solution is obtained. Then the author explains the problems of the continuous rigid frame bridge during its operation stages. It turns out that the stability of the bridge structure is similar to that of the steel frame and can be solved with the compressive bar stable theory for the completion of the continuous rigid frame bridge.2. Then the author firstly introduced the finite element method to solve the problems of the stability of the bridge structure. With the method, the corresponding equations of the stability are deduced. What’s more, the author has made an analysis of the No.3bridge in Huashan during its construction phrase and the completion stage. The results show that:1) The safety factor is decreasing from the stage of naked pier. And the factor reaches its minimum value when the bridge is of the largest double cantilever. That is the most unstable stage.2) When the bridge folds together, the structure system turns to be continuous one from the cantilever system. The integrity is strengthened and the safety factor also increases.3. The vehicle-bridge oscillatory differential equations of4degrees of freedom which are widely used for highways are deduced with D’Alembert theory. Then the oscillatory differential equations of the bridge are also obtained according to the finite element theory. And the model of the vehicle-bridge vibration is also built with the contact theory of the vehicle-bridge vibration.4. The density of power spectrum for irregular road surface and relevant standards are all interpreted. The irregular degree of the road surface is simulated with the harmonic synthesis method. And the space sample curve is also figured out for the irregular degree of road surface.5. Trough all the analysis, it shows that the vibration response and the impact coefficient are accordingly increasing along with the increase of the velocity. When the speed is60km/s, the displacement of the right bridge is apparently large. When the speed is60km/s, the tortion frequencies of the vehicle is1.006Hz and it is closed to the first order of the vertical vibration fundamental frequency,0.9365Hz. Thus the first kind of resonance is obtained.6. Trough the calculation, it can also show that irregularity of road surface effects the vibration of the bridge strikingly. At the road surface of D level, the biggest impact coefficient can reach1.428. Therefore, during the operation stage, the bridge deck pavement should be carefully protected in order to avoid the damage of the bridge when the vibration response is too big under the vehicle load as the road surface is pretty irregular.