Study On The Evaluation Of The Bearing Capacity Of Prestressed Concrete Beams After Cracking Based On Model Correction

As the key project of the transportation system,the detection and evaluation of the safety performance of the bridge is of great significance to ensure the safety of the existing bridge.Prestressed concrete simple supported beam bridge is widely used in highway,railway and urban roads in China,The investigation shows that the technical state of bridge for a long time,many of the high grade highway in China and the operation of the city roads,prestressed concrete bridges there are quite a number of diseases and damage to a certain extent,affect the normal operation of the bridge structure and the use of security.Theoretical analysis and Experimental Research on the current domestic bearing capacity of prestressed concrete bridge after cracking evaluation method is relatively backward,Therefore,the research on the damage assessment method of the prestressed concrete bridge is still the hot topic of the bridge engineering industry at home and abroad.Based on the relevant experimental data of a scientific research project,the effectiveness and applicability of the response surface method based on the finite element model(RSM)applied to the static performance evaluation of prestressed concrete simply supported beam after crack are discussed.Based on the finite element model,the response surface model is built,and the measured deflection data of the static load test is taken as the objective function.Evaluation of damage degree and evolution of flexural stiffness of prestressed concrete simply supported beambased on response surface model.The main work of this paper is as follows:1)Laboratory scale model static load test:Based on the 20 m span T-beam standard commonly used in China's highway,a multi-test beam was fabricated according to the proportion of a certain scale,beam configuration and post tensioned steel strand with different prestress,and using the two-point symmetrical loading method.Select the test beam that has been loaded into the crack for secondary loading.The developmental and variable rules of the test beam in the working stage with cracks was measured,such as the displacement of the 1/4L,the middle span,the 3/4L section,the strain on the upper and the lower edge of the cross section and cracks in cross section of pure bending section.In this paper,the relevant experimental data are collated and analyzed to provide the basic experimental data for the following research work.2)finite element model direct correction method:The initial finite element model is established by taking the laboratory prestressed concrete beam as the research object,sensitivity analysis is used to select the structural parameters with high sensitivity as the design variables.The static variable function is used as the state variable to construct the static objective function,and the initial finite element model is modified.Then according to the static test loading condition,simulation analysis and calculation results of strain and deflection test beam finite element model of the control section of each loading,and compared with the results of static load test,the error meets the requirement of Engineering precision.It is shown that the finite element model based on the measured deflection data of static load test can be used for structural state assessment.3)Finite element model updating method based on response surface method:This paper introduces the basic principle and steps of the response surface method to modify the finite element model,and several commonly used experimental design methods are compared.The finite element model is modified based on response surface method,compared with the direct correction method,the response surface model updating method has the advantages of fast convergence speed,intuitive numerical analysis,and explicit function relation can be constructed,which has significant application value.4)Damage assessment of bending stiffness based on response surface method:Firstly,the response surface method based on finite element model is used to simulate the damage identification according to the test beam.Then the finite element model is used to construct the response surface model,the objective function is established based on the measured deflection data of two cracked test beams,and research on the application of response surface method based on finite element model to the evaluation of flexural rigidityof prestressed concrete beams after cracking.The research results have some reference value.