Updating And Carrying Capacity Assessment Of Bridge Finite Element Model Based On Bridge Load Test

At present,the application of structure analysis model based on finite element method for bridge structure is widely recognized.In particular,finite element modeling is used to analyze the structure of the bridge,which is not able to carry out the analytical calculation,such as the large span,the complicated structure and the multi-static structure.However,due to the often used when establishing finite element model a lot of equivalent simplification,the material parameter selection,the unit type selection,boundary conditions,simulation and so unable to realize the real simulation of structure.Therefore the establishment of a bridge structure that accurately reflect the actual characteristics of the finite element calculation model of long-span Bridges,special structure and many bridge health monitoring and damage detection of the Bridges in service is the key point to the static and dynamic calculation and analysis.In order to improve the accuracy of bridge health assessment and provide date for the bridge's reinforcement design and long-term health monitoring.This paper is based on the static bridge finite element model correction theory,using BP neural network program which is based on MATLAB software to modify finite element model parameters of Bridges,in the first stage we update the finite element model on bridge dead load and the second stage by using BP neural network for fixed bridge finite element model of the whole stiffness to improve the accuracy of finite element model of bridge.The updated finite element model is verified which is updated based on the measured data of the bridge and the carrying capacity of the bridge model.The results can be seen from the comparison of the deflection value and the calculated deflection value and the calculated deflection value,The calculated value of the updated finite element model is between the measured value and the unupdated calculated value of finite element model,The relative difference between the calculated deflection value of the bridge was decreased from 33%?14%to 11%?4.7%;Measured bridge first-order natural frequency is 1.758 Hz,The first-order natural frequency of original bridge is 2.135 Hz,The first-order natural frequency of updated bridge is 1.859 Hz,frequency error is decreased from 21.44%to 5.75%and less than 10%of the general requirements,the above data show that the correct bridge finite element model updating.The structural ultimate load capacity,crack resistance and the overall stiffness of the bridge are checked by MIDAS CIVIL:When the bridge is completed,the lower margin of the whole bridge is equipped with sufficient compressive stress;Girder under normal use limit state of each control section are not beyond prestressed concrete component specification requires that all housings(tensile stress value of 0 MPa),main girder maximum compressive stress is 9.2 MPa,less than the standard value(17.5 MPa),main girder control section minimum compressive reserves of 4.0 MPa,meet the specification requirements;Girder under normal use limit state of each control section are not beyond prestressed concrete component specification requires that all housings(tensile stress value of 0 MPa),main girder maximum compressive stress is 9.2 MPa,less than the standard value(17.5 MPa),main girder control section minimum compressive reserves of 4.0 MPa,meet the specification requirements;The maximum main tensile stress of the box girder is 1.4 MPa,which is less than the standard allowable value(2.4 MPa),and the maximum main stress is 6.9 MPa,which is less than the standard allowable value(21 MPa);The maximum displacement and minimum displacement of the superstructure of the bridge are 0.02 m,which is less than the main cross allowable value L/600=0.075 m,and the deformation of the main girder meets the standard requirements;Based on the bridge in the carrying capacity calculation analysis shows that the flexural bearing capacity under the limit state security reserve coefficient is 1.14?2.23,the shear bearing capacity of safety coefficient is 1.14?1.19,meet the specification requirements;The above data shows that the bridge finite element model bearing capacity meets the design and specification requirements.The results show that the bridge finite element model is updated and the model carrying capacity is meet the requirements of design and specification.The finite element method used in this paper is simple and reliable,high computational efficiency and easy to be realized in engineering practice,so as to provide a reference for the application of finite element model of bridge in engineering practice.