Sensitivity Analysis For Construction Parameters And Finite Element Model Modification In Closure Jacking Stage Of Continuous Rigid Frame Bridge

Closure jacking is the key process in the construction of prestressed concrete continuous rigid frame bridge.The successful bridge construction depends on the construction quality of closure jacking.In order to ensure the safety of the closure pushing process,the finite element model of the closure pushing of the bridge is established at first.Through the calculation and analysis,the theoretical displacement value under the action of all levels of the jacking force is obtained,so as to monitor and control the jacking process.However,there is a big discrepancy between the actual jacking displacement and the theoretical value.The reason is that the finite element model based on the design parameters cannot accurately reflect the actual state of the structure.As a result,the closure jacking effect cannot be effectively guaranteed.In this paper,the research background is the closure and jacking construction of a seven span prestressed concrete continuous rigid frame bridge.The main research contents are as follows:(1)The initial finite element model of a seven span prestressed concrete continuous rigid frame bridge was established.The numerical simulation of the jacking process of the closure section was carried out.The finite element value of the horizontal displacement of the pier top under the action of the graded jacking force was compared with the measured value,and the difference between the initial finite element model and the actual structure was analyzed.(2)From three aspects of material characteristics,load action and boundary conditions,10 influencing parameters were selected,and horizontal displacement of pier-top in jacking construction,horizontal displacement of pier-top in completed bridge,and bending moment of the pier-bottom in completed bridge were taken as evaluation indexes to roughly judge the sensitivity of the selected parameters.The main parameters that affect the horizontal displacement of pier-top in jacking construction are the elastic modulus E2 of the pier concrete,the DX of the bearing platform bottom,and the RY spring stiffness;the main parameters that affect the horizontal displacement of pier-top in completed bridge are the elastic modulus E2 of the pier concrete;the main parameters that affect the bending moment of the pier-bottom in completed bridge are the unit weight γ1 of the main beam concrete.(3)Based on the main parameters obtained from the sensitivity analysis,the initial finite element model was modified by using the horizontal displacement monitoring data of the top-pier in closure pushing construction combined with the response surface method.The objective function of the residual displacement of the closure pusher was constructed,and the constraint optimization problem of the structure was solved with the help of Matlab optimization tool,and the optimal correction parameters are obtained.The modified parameters were substituted into the initial finite element model for calculation and analysis,and the modified closure push displacement was obtained,and compared with the measured data to verify the accuracy of the modification of closure push finite element model.In addition,on the basis of response surface modification,Monte Carlo method was used to simulate the measurement error,and the influence of measurement error on the modified results was studied.