Research On Fatigue Performance Of Existing RC Bridge Under Overloading

With the development of transportation business and the highway, bridge level, the vehicle loads in bridge structure have constantly grown. So the phenomenon of overloading in RC bridge actually exists, and does ignoring fatigue damage in bridge structure.In this paper, based on the existing measured survey conclusion of highway traffic overloading vehicles, introducing equivalence principle of fatigue damage, refined a more practical frequency value spectrum of model vehicle load. Drawn the namely fatigue load simplified model with engineering application under overload operation. Then transformed witch into several stress level overloads. Realized transforming random cycle loads into multistage luffing cycle loads. In addition, with practical engineering displaying the whole calculation process, it can be easily applied to fatigue cumulative damage model, and fatigue life of bridge is predicted.One core of fatigue damage study is to determining the correct and convenient fatigue damage variables according to the research needs. This paper briefly introduced several typical fatigue damage variables, and from the basic theory of damage mechanics, established new damage variables, provides a fairly good theoretical basis for concrete fatigue damage equation and life prediction.Build material fatigue damage accumulation model: 1) Based on nonlinear damage and fixed linear fatigue accumulating damage models Separately from Manson bilinear model and revised Miner rule. Considering the influences of stress level, loading sequence and damage evolution process, Established a nonlinear dynamic system to calculate fatigue cumulative damage. Put forward nonlinear damage accumulation model of concrete. Then get surplus fatigue life prediction in multistage fatigue loading luffing. 2) Put forward reinforced damage mechanisms.Correct nominal stress method of fatigue life analysis, to establish a damage theory analysis law based on material fatigue curve and linear fatigue accumulating damage theory, contrast structures'Load course under Overloading function, to determine the fatigue life of structure. Then gives overload operation in existing reinforced concrete bridges under structural fatigue residual life calculation steps. And then put forward the fatigue residual life calculation steps of existing RC bridge under overload operation.Based on the proposed concrete damage model and life prediction method, the paper finally compared its calculated damage and fatigue life with others test values. Calculations showed that Error is within the permitted in engineering, which explained that the damage model and fatigue life models put forward in this paper are correct, and compared the results from miner rule which is widely applied in engineering calculation, which error greatly decreases. So the fatigue damage model form this paper is practical and versatile, which can be applied to the damage analysis and life prediction calculation of existing RC bridge.