Finite Element Model Updating of Box Girder Bridges with Corrugated Steel Webs

In order to reduce the error between the finite element values and measured values of the box girder bridge with corrugated steel webs, a bridge finite element model updating method using response surface method and Fmincon algorithm was presented, taking a box girder bridge with corrugated steel webs in the connecting line of Jingzhong airport in Gansu province, China as the research object. Firstly, static and dynamic load tests were carried out to obtain the measured values of bending vibration frequency, deflection and strain. Secondly, the calculated values of these parameters were obtained by the finite element modeling using solid and plate-shell elements, respectively. After comparison of the calculated values with the measured values, a more accurate solid finite element model was selected as the updated initial finite element model. Then, on the basis of reasonable selection of design parameters, the corresponding structural response was obtained through the central composite test design, the quadratic polynomial regression equation between the structural response and design parameters was obtained by least square method fitting, and the objective function of the difference between the measured value of the target response and the corresponding response was constructed. Finally, Fmincon algorithm was used to calculate the objective function iteratively, and the updated value of parameters and the baseline finite element model of the bridge were obtained. The results show that it is feasible to modify the finite element model of the composite box girder bridge with corrugated steel webs by combining the response surface method and the Fmincon algorithm, which has the characteristics of simple modification process and fast convergence speed. The calculation time was within 0.25–0.75 s, and the relative error of the first-order bending vibration frequency was updated from 4.85% to 1.62%–2.91% according to different response combinations. Through the comparison between Genetic algorithm and Fmincon algorithm, it was found that Fmincon algorithm improves the model updating efficiency significantly, which can provide reference for the finite element modeling analysis and mechanical performance analysis of this kind of bridges in engineering practices.