Study On Fatigue Numerical Analysis Method Of Reinforced Concrete Bridge Slab

With transportation infrastructure construction improving, the bridges are more and more applied in the high-speed railway, highway and city light rail as an important part. However, now the vehicle traffic grows rapidly, loading levels increase significantly, the fatigue problem of bridge also reveals obviously.The bridges support various of vehicle loading effect, so their whole working lives are equal to the process of accumulated damage under vehicles. As the upper structure of bridge, the bridge slab is directly under action of vehicles, which is prone to fatigue damage so that imperil traffic safety. So it is of great significance for the whole bridge's use of security that research degenerate rule of material, accurately identify whether the bridge deck is fatigue damage, and take measures to reinforce.In this thesis, vehicle load was simplify treated. The forms of axle load were used to affect on the bridge slab and some internal force amplitudes were get, which were converted to regular amplitudes by the rain-flow method. Then these regular amplitudes were combined into an equivalent amplitude, which was equivalent fatigue load. By this method, the complicated vehicle loads were translated in the case of slab's damage was invariant, so the progress of fatigue numerical simulation was greatly simplified.In this thesis, the elastic module of concrete attenuated constantly in the whole progress of fatigue was considered, which based on constitutive under static load in concrete specification. The compression and tension fatigue constitutive of concrete were deduced by test data and degraded formulas of fatigue parameters; Degradation of steel through the whole fatigue progress was considered by means of the operational area decreased can be thought as fatigue parameter; The full-range fatigue analytical method was improved, and division of load step was optimized, so analysis speed was accelerated when the result's accuracy was got to be promised.In this thesis, fatigue numerical simulation of a trial slab and a practical slab was carried out by finite element software ABAQUS. Reliability of derivational fatigue constitutive was inspected. The full-range fatigue analytical and designed method was submitted, and fatigue life of the practical slab was predicted. Cross-section fatigue properties of reinforced concrete slabs were researched. As can be known, plane cross-section assumption could be used under repeated load. Fatigue degradation of concrete presented three-stage variation, and the main reason of concrete's damage was accumulation of residual strain; Operational area of steel decreased constantly in the whole loading, interaction between steel and concrete weakened gradually, so that stress of steel increased to yield strength, which lead to damage of steel.