Analysis Of Damage Causes And Diagnosis Of Double Arch Bridge

Double arch bridges are the most models of arch bridges built in our country in 1960s.Beacaus of the merits in this structure, such as novelty, legerity, saving material, convenient for construction, they spread all over the country and was applied in a large quantities. They made a great contribute for the development of our country's highway and bridge causes. But the double arch bridges have demerits, for the design lever and the load criterions on the low side then, and the steel is scarce in the structure. When the bridges are loaded heavily, and in heavy traffic for long time, most of them are damage. How to deal with the bridges in damage is one of the most concerned problems.To evaluate the damage statues of the bridges in theory, we must know the mechanic characteristics of the structures in varies of circumstance and have the knowledge of identification and orientation of the given damages, so that we can make decision of maintenance and deploy resource more reasonably. These years the accidents of structure damages and aging increase around the world; the diagnosis and analysis of bridges come to a point.This paper analyzes the reason of the double arch bridge's damages in theory, combined with the maintenance and reinforcement project of Yellow Dragon Bridge. The paper build a plane model of the whole bridge based on the FEM, and analyze the internal force and structural displacement changes in every damage circumstance. The data reflect that the damages in arch rib in the tip will make internal force of some sections increased, accordingly the stability and the durability of the structure reduce; the damages in the arch foot will change the structure system; and the displacements of abutments will develop great accessional internal force, and deform the main arch and even crack, accordingly change the system of the structure. Recognizing damages belongs to reverse problem in mechanics. Reverse problems are that getting reasons from results, which may cause ill-posed. We can solve the high non-linear problems with Genetic Algorithm. Genetic Algorithm is an optimalsolution searching method simulated natural evolution. It can find the optimal solution in entire range other than customary optimized method. This paper have identifications to the whole bridge with Genetic Algorithm, the data indicate that the method to identify the damages of the double arch is precise.This paper is combined with the merits both of FEM and GA, and has analysis of both positive and negative. The method and the result are worth of the maintenance and reinforcement.