Study On Reinforcement Effect Of T-beam With External Prestressing

With the large-scale construction and operation of highway bridges,due to the influence of the external environment,the defects of the structure itself and the service load,the bridge structures have appeared the problems of deterioration of service performance,deterioration of safety and durability etc,the number of dangerous bridges is increasing rapidly,and the maintenance and reinforcement of bridges are developing rapidly.On this basis,this paper mainly studies the simulation calculation of the effect of external prestressed reinforcement and the improvement of the bearing capacity of the bridge after reinforcement,and comprehensively analyzes the reinforcement effect of external prestressed reinforcement.In this paper,the influence of external prestressing reinforcement on stress and deflection of bridge is analyzed by finite element simulation calculation,and the strain and deflection are monitored and measured,after strengthening the bridge load test and bearing capacity check to verify its strengthening effect,analyzed the factors affecting external prestressed reinforcement,and calculated the final effective prestress.Firstly,this paper introduces the basic principle and design idea of t-beam external prestress strengthening method,and analyzes the changes of stress and deflection of the strengthened main beam through finite element simulation,then through the construction monitoring to verify the effect of external prestressed reinforcement,then the bridge load test and load-bearing capacity check to assess whether the bridge meets the requirements of the code,and finally analyze the factors that affect the effective external prestressed,calculate the final effective prestress.The results of structural simulation show that when the tensile force meets the design requirements,the accumulative stress variation of the bottom plate of the 1～5#beam is between 7.4 MPa and 8.5 MPa,and the deviation between the actual and theoretical elongation of the prestressed steel beam is less than 6% The strain check coefficient of the main girder is between0.60 and 0.87,and the deflection check coefficient is between 0.71 and 0.89.After reinforcement,the mechanical performance of the bridge meets the requirements of the current code,the dynamic response of the structure meets the requirement of service,and the calculation of the bearing capacity shows that the bending bearing capacity and the shear bearing capacity of the strengthened bridge meet the requirement,but the safety reserve of the bending bearing capacity is insufficient.By comparing the measured values of strain and deflection of the bridge after tensioning with the theoretical values,it is found that the measured values of deflection and compressive strain are less than the theoretical values,which shows that there is a loss of prestress in thecourse of tensioning,according to the above-mentioned situation,this paper puts forward four factors that affect the prestress loss:(1)The prestress loss caused by the friction between the prestress bundle and the pipe in the course of stretching;(2)The prestress loss caused by shrinkage of prestress bundle and deformation of Anchorage,(3)the prestress loss caused by batch tension,(4)the prestress loss caused by relaxation of prestress reinforcement,etc.,comprehensive analysis of the loss of prestress factors,and calculate the final effective prestress.