Development of a Combined Finite Element/Finite Strip Method to Analysis the Long-Span Box Bridge Having Diaphragm

This paper presents a low-cost combined finite element/finite strip method to simulate and analysis of long span box bridge with internal diaphragm. In this regard, the finite element method was used to simulate the bridge and the diaphragms were modeled using finite element method. The displacement-strain relationships were derived based on the first shear deformation theory. The Lagrange multiplication factors were used to apply the displacement boundary condition on the connection between the diaphragm and the bridge. The bridge was subjected to two types of loading (concentrate and distributed loads). The stiffness matrix and load vector of the diaphragms were computed on the global coordinate system. The stiffness matrix and load vector of the bridge was obtained in local coordinate system. The stiffness matrix and load vector of the bridge were transferred into the global coordinate system using the transformation matrix. The responses of the bridge and diaphragm (such as deflection, internal forces and stresses) were computed using the static analysis. The bridge response obtained from the method developed in this study was compared with that obtained from ABAQUS software (a fully finite element model of the bridge and diaphragm) in order to prove the validity of the results computed by the approach developed in this paper. The comparison shows that although a negligible difference is seen between the results obtained from the ABAQUS and the proposed method, the computational cost of the ABAUQS model is significantly greater than that of the method developed in this study. The effects of loading type, number of elements, bridge cross section and diaphragm on the bridge response were investigated. The results show that the diaphragm increases the bridge torsional resistance. Moreover, when an asymmetric point load was applied to the bridge, the bridge rotation was significantly decreased using the diaphragm.