Existing Bridge Condition Assessment Based On Crack Characteristics

Bridges as communications hinge, its safety performance and operation status are relating the national economy development, and there are having the bridge accident more and often, which has relations with the bridge structure damage, aging causing the carrying capacity to insufficient and the degeneration of stiffness. Therefore, the assessment of existing bridge structure state has become the one of most popular topics in the project domain now.In this paper, bridge structure evaluation research situation and development tendency are introduced first, and then expounded the methods of evaluation in common at present, discussed the advantages and the practicability about them. And put forward the methods of the crack state evaluation based on the characteristics of the bridge structure, combining the state evaluation of bridge and the feasibility of this method has been verified. Meanwhile, cracking of concrete structure formation, fracture mechanism and fracture analysis method are introduced, thinking statistics method is simple, applicable and has certain reliability.In the dissertation, analog simulation of the finite element about the specimens loading process was introduced. The results of the mid span deflection, section stress and the development of cracking were a better agreement between the finite element analysis and the trial, and the validity of the finite element model was validated. And the equation of the tensile reinforced stress and the loading rate was derived.With the analog simulation of the finite element about the specimens, analysis of crack characteristics parameters on the effect of tensile reinforced stress was processed, and esbablished the relationalship between the parameters of cracking characteristics and the tensile reinforced stress. With reinforcement stress as intermediary, it derived the equation of the crack characteristics parameters and the loading rate.The equation of crack height and flexural rigidity was deduced based on RC beam mechanical theory. The theoretical calculation method and load-deflection method was proposed combining with test and finite element analysis, and the regression equation of the crack characteristics parameters and the stiffness reduction factors was introduced.At last, the carrying capacity and stiffness of the existing bridge were assessed using the method recommended in this paper, the results of the assessment proved that the method of the assessment in this paper is effective and feasible.