The In Servie Prestressed Concrete Bridge Structure Analysis And Residual Bearing Capacity Assessment

In nearly ten years,with the widely used of high-performance concrete and high strength steel, Prestressed concrete bridges have continuously developed towards the direction of long-span, light and high-performance which greatly promote China's bridge construction. Prestressed concrete bridge today boasts its dominant position in highway bridge field in our country. At the same time, with its continued rapid development and the elapse of serviced time, we must see the increasingly serious situation in degeneration of bridge's property, insufficient bearing force, etc. Therefore, it becomes increasingly urgent to analyze the present condition and assess the carrying capacity of prestressed concrete bridge structure. Thus, it has significant meaning to have an in-depth study of the prestressed concrete bridge structure in service.This paper aims at evaluating the present durability and over carrying capacity by using the finite element analysis program and the scene and indoor experimental data on the background of a simple-supported prestressed concrete core slab bridge which has serviced for 14 years in Jiao Zhou bay expressway of Qingdao, which would offer reference for future similar.There are introduced in detail about the mechanism and theoretical models of the main factors of the existing concrete bridge durability. On this basis, some samples obtained by the current structure of prestressed concrete beams. the carbonization depth, Chlorine ion content and distribution and compressive properties of these concrete samples be tested and the corresponding durability prediction model is used to forecasted the development rule during service period. The test results showed that the bridge bridge durability, but the weak point of the durability was chlorine ion content at the position of beam orer obtuse Angle.The stress was released at the quartile and middle of the beam. Based on the method of stress release,existing stress value of the concrete under the beam could be obtained under the gravity and prestressing. The physical model of monospar was analysed by finite element method, and the model was proved reasonable. Deterioration of the material after long-term service was taken into the account, and the ultimate bearing capacity was analysed by the nonlinear mothed. The bearing capacity of monospar at current situation and after long term service were obtained and assessed. The results indicated that the ultimate bearing capacity of the structure was not significantly reduced after long-term service. The ultimate bearing capacity of monospar where tensile stress does not appear to limit state did not meet the requirements according to the fundamental combination. There is no cracks formed by tensile stress, with which as the standard, the bearing capacity of monospar could meet requirements. However, safety reserve was small.The test of the structure self-oscillation characteristics was taking on the scene under the earth self-oscillation. It collects natural frequency of vibration and uses spectral analysis and cross-spectral analysis to get the first natural frequency of vibration; Established the superstructure model of the whole bridge in grillage method, combined with test value of first-order frequency, to assess structure stiffness. Results showed that, there is still a certain status structure stiffness reserves. Analyzes the variation law of structure vibration characteristics under different conditions simulation of damage and material degradation. Analysis found that, midspan damage on structure vibration frequency influence greater than four fold point of span in the same degree, and it has had the higher susceptibility of higher-order frequency. In the short term, the effect is not obvious of structure vibration characteristics as a result of strength of concrete changes of considering long-term of the material degradation.