External Prestressed Reinforcement Design And Stress Analysis Of Continuous Rigid Frame

Long span prestressed continuous rigid frame bridge is widely used in bridge construction due to its advantages of large structural rigidity,simple and beautiful shape,small expansion joint,good integrity and easy maintenance.However,with the increase of service life,long-span continuous rigid frame bridges begin to appear some diseases.The most prominent diseases are beam cracking and midspan deflection,and they affect each other.Without improvement,a vicious circle will be formed,which will affect the stress state of the bridge structure and endanger the driving safety.The research shows that the most effective method for the continuous rigid frame bridge is external prestressed reinforcement.However,due to the influence of design scheme,construction technology,environment and other factors,the external prestressed reinforcement sometimes fails to achieve the expected effect,and even causes further damage to the bridge structure,which can not be saved.Therefore,based on the finite element simulation method,how to find the appropriate balance point between the application of prestress,deflection lifting and local stress,and then optimize the design of external prestressed reinforcement,to ensure the effect of external prestressed reinforcement of long-span prestressed continuous rigid frame bridge is an urgent work.Based on a bridge,this paper uses the finite element software MIDAS civil and the bridge doctor to establish a numerical model to simulate the disease state.By changing the relevant variables,an effective linear layout scheme of external tendons and the number of prestressed tendons are proposed,and the method is verified and analyzed based on the actual project.The main research contents of this paper are as follows:(1)based on a large number of research and literature review at home and abroad,the common disease types and reinforcement methods of long-span prestressed continuous rigid frame bridge are systematically analyzed.Based on Midas,a numerical model of the actual bridge structure is established,and the disease state of the bridge is simulated by the loss of longitudinal prestressing force.By studying the external tendons of different specifications and materials,different tensile forces,different total area of steel tendons,different positions of steel tendons,the increase of corresponding stress and deflection,the optimal external prestressing reinforcement scheme is proposed;(2)Using the bridge doctor to establish the numerical model of the bridge structure relied on,applying external prestressing force to the model after simulating the disease again,studying the influence of external prestressing tendon arrangement scheme and external prestressing tension on the stress increase and deflection increase of the strengthened bridge beam,and comparing and analyzing the calculation results of Midas model,studying the kiss of the calculation results of the two numerical calculation methods;(3)based on the actual prestressed continuous rigid frame bridge reinforcement project,the damage numerical model is established firstly,and the optimal design scheme is determined based on the numerical model,then the reinforcement scheme is applied to the project example,and the reinforcement effect of the optimization scheme determined by the numerical simulation method is verified by the actual reinforcement effect.