Calculation of Transverse Load Distribution of Multi-beam Short Box Girder Bridge Considering Influence of Torsional Resistance

To calculate the transverse load distribution of a multi-beam low box girder bridge, both the rigid-jointed beam method and numerical calculations are generally adopted. However, these methods do not consider the torsion of the main girder and the wing plate. Hence, the rigid-jointed beam method and finite element modeling calculation analysis can not accurately simulate the characteristics of the structure, which creates some deviations in the evaluation of the technical condition and bearing capacity of the bridge. In this study, based on the calculation method of the load transverse distribution by the rigid-jointed beam method, a calculation method of load transverse distribution suitable for a multi-beam low girder bridge is proposed by considering the restrained torsion action of the main beam and wing plate when forming the flexibility coefficient matrix. To verify the correctness of the method, a 20 m prefabricated box girder bridge was sampled, and verifies the correctness of this method by using the considering torsional stiffness and not considering torsional stiffness of rigid-jointed beam methods, the finite element numerical simulation method, the field test results. The results show that the accuracy of the calculation results for the load transverse distribution method adopted in this study is higher than that of the calculation method of the rigid-jointed beam method without considering the torsion of the main girder and wing plate of the box girder. Additionally, it is closer to the mechanical characteristics of a real bridge compared to the traditional calculation method. Meanwhile, the calculation results of grillage and plate element models are basically the same as calculation results of the transverse distribution presented in this study. In evaluating the transverse distribution of deflection or strain, the three methods were relatively close. This shows that the calculation results of the transverse distribution presented in this study are closer to the field test values than those of the grillage and plate element models. Furthermore, the deviation between the calculated results and the experimental values of the transverse distribution under the three methods is less than 20%. Above all, in the field test and evaluation of the bridge bearing capacity, the numerical calculation method of the complex finite element model can be replaced by the method presented in this study, which provides a more accurate theoretical reference for the field test of a prefabricated low box girder bridge and evaluation of bridge technique condition and bearing capacity. © 2020, Editorial Department of China Journal of Highway and Transport. All right reserved.