Study On Fracture Mechanism And Service Life Of Prestress Bar Under Fatigue Load And Corrosive Media

Prestressed concrete structures due to the advantages of good mechanical performance、 construction fas、safe,by more and more applied to the bridge, tunnel and slope anchoring engineering. External environment of the engineering is complex,often at the same time under fatigue loading and the coupling effect of corrosive medium,prestressed structural fatigue fracture may occur suddenly in this case,to the project itself and the people’s lives and property posed a serious threat.Based on the traffic in shandong province science and technology innovation project "prestressed structure under fatigue loading and the coupling effect of corrosive long-term performance study" (NO.2010 Y08-3) as the backing,Through test and theoretical analysis,under the action of the fatigue load and the corrosive medium coupling prestress of the rod body fatigue corrosive performance was studied, analyses the corrosive fatigue fracture mechanism,and based on neural network algorithm to predict the actual service life of the prestressed anchorage structure.The concrete research content is as follows:(1)In different times reinforced specimen axial tensile fatigue test basis,respectively for acidic and alkaline environments of indoor accelerated corrosive test,research different fatigue loading times, different corrosive media and corrosive time affects the quantity of steel bar corrosive per unit length,the three factors influence regulation of the corrosive of steel per unit length.(2)Choose typical reinforced specimen, tensile fracture experiment was carried out,the analysis of the effect of corrosive and fatigue of steel mechanical properties,using scanning electron microscopy (sem) to the reinforcement fracture observation,analyzes the corrosive medium and fatigue load under the action of coupling macro micro mechanism of reinforcement fracture.(3)Using two training function,Genetic optimization of BP neural network model is set up, respectively,and application of laboratory test data to evaluate the two models, choose the suitable model, to determine the structure of the model.combined with long-term monitoring data actually works on this basis,application of neural network prediction model, service life of the actual prestressed anchoring engineering made a preliminary forecast.