Evaluation Of Bearing Capacity Of Reinforced Concrete Beam Bridge Based On Degradation Of Material Properties

The reinforced concrete beam bridge is widely used in traffic construction because of its convenient material selection and low cost.However,the mechanical properties of the two main materials,steel bar and concrete,will decrease with the increase of service life,the change of ambient temperature and humidity,and the effect of external load.Therefore,it is very important to know the actual bearing capacity of bridge for bridge operation and reinforcement.At present,there are two commonly used methods to evaluate the bridge bearing capacity: The first one is from the factors that influence the degradation of the bridge performance,combined with the evaluation results of the bridge technical condition,the model of bridge bearing capacity based on the deterioration of material properties is established.The second method is to determine the bridge bearing capacity by using the bridge load test to detect the bridge stress,deflection,cracks and other data.This paper combines the above two methods to confirm the bearing capacity of the bridge.The steps are as follows:（1）study on evaluation result of bridge technical conditionBased on the evaluation results of the technical condition of the simply supported Beam Bridge Bridge in Sichuan Province,the bridge which was evaluated by three testing engineers at the same time was selected.In this paper,two groups of data are obtained by evaluating the grade of bridge according to the current urban bridge evaluation criterion and Highway Bridge Evaluation Criterion.According to the method of degree analysis,a set of data is obtained from the evaluation results of bridges by 3 testing engineers.Three groups of data were compared to determine the accuracy of the existing detection data.（2）prediction of deterioration of bridge materialsIn the process of data statistics,the testing data of reinforced concrete bridge materials are eliminated if the deviation between the testing data and the testing data of material properties is more than 3 times standard deviation under the condition of the same service life,the obtained average value is taken as the measured value of material properties for the service life.By comparing the measured data of material properties with the predicted data in the previous papers,the prediction model of material degradation suitable for Sichuan area is obtained.（3）building and checking calculation of bridge bearing capacity damage modelAssessment of the technical condition of a 15-year-old reinforced concrete beam bridge and testing of its material performance parameters.The finite element model of the bridge is established by using the software Midas-Civil,and the bearing capacity of the bridge model is reduced by the degradation parameters such as material property detection value,model prediction value,model modification value,etc.three damage models with load-carrying capacity reduction are obtained.Three damage models were used to calculate the structural resistance of the bridge.（4）the bridge load test verifies the damage model accuracyThe stress,strain and deflection of the bridge were tested by load test,and the calibration coefficients of the corresponding parameters were calculated.It is found that the check coefficient of load test is closer to the check data of damage model of bearing capacity of bridge modified by material properties.According to the results of damage model and load test,it is proved that the modification of material property model in this paper is in accordance with practical engineering.