| Bridge is an important infrastructure project of the country,and it is also an important part of lifeline engineering.It plays a more and more important role in the whole national economy.In the process of long-term operation,the reduction of bearing capacity exists in bridges generally due to the degradation of the material properties.Therefore,there is a great security risk which can even cause the collapse of bridges and other disastrous consequences.So,it is very important to evaluate the actual bearing capacity of the existing bridge in time.This paper analyzes the bearing capacity of existing RC beam bridges,and studies the simplified analysis method of the ultimate bearing capacity for existing RC simply supported T beam bridges.Specific work is as follows:1.Considering the influence of concrete carbonation and chloride ion corrosion on the corrosion of the rebars respectively,the bearing capacity of existing RC beam bridges is analyzed with the degradation of the rebar section,the rebar strength and the rebar/concrete bond performance.A complete analysis flow of bearing capacity is carried out,and the sensitivity analysis of the factors affecting the calculation of bearing capacity is carried out.2.For the existing RC beam bridges,a calculation process of system reliability for bearing capacity is put forward.Considering bending failure and shear failure of the RC beam bridges,the reliability index of the structural member after degradation is calculated according to JC method and MC method firstly.Then,the comprehensive reliability index of the structural member is calculated using narrow boundary method.At last,its system reliability index and failure probability of the bearing capacity are analyzed by calculating the weight of each structural member using the failure index.3.General finite element software ANSYS is used to analyze the RC bridges.The constitutive relation of material is introduced by considering the effect of material properties degradation.The bond slip between rebars and concrete is simulated by using nonlinear spring element.The ultimate bearing capacity of the RC bridges is analyzed using the finite element model based on the system of beam element-rigid arm element-spring element-rebar element.4.For the existing RC simply supported T beam bridges,the relationship between the parameters affecting the ultimate bearing capacity and the ultimate bearing capacity of the single beam is analyzed using the finite element model based on the system of beam element-rigid arm element-spring element-rebar element in order to deduce the calculation formula for the ultimate bearing capacity of the single beam.Than the fast calculation formula for the ultimate bearing capacity of the simply supported T beam bridges is analyzed based on the calculation formula for the single beam.At last,the correctness and reliability of the calculation formula are analyzed by comparing the results of ANSYS and the formula. |
