Orthotropic Analysis Of Steel Deck-girder-rib System Subjected To Transverse Load

A steel deck-girder-rib bridge system subjected to the transverse load is investigated in this paper. So far, theoretical studies of deck-girder-rib bridge system are based on a hypothesis that the stiffness of girders is infinite. In practice, however, the stiffness of girders is not infinite. For this reason, we perform the study for the mechanical behaviors of a deck-girder-rib bridge system in which girders of finite stiffness are considered. The bridge deck under uniformly distributed load is laid on four simply-supported girders at the four edges and is reinforced by ribs in longitudinal direction.Based on the Mechanics of Composite Material Mechanics and Elastic Theories for Plates and Shells, a longitudinally stiffened deck is idealized as an orthotropic plate. The equivalent material properties in the longitudinal and breadth directions of the orthotropic plate are evaluated by treating the ribs as reinforcing fiber-beams. Governing equations after the transformation are derived according to Kirchhoff’s assumption. Deflections of girders under the load are obtained from the theory of mechanics of material. With the available solutions of the deflection of the girder, deflection of the deck is proposed by considering the continuity of deflection between the deck and the girders. Governing equations for the deck-girder-rib bridge systems are solved using Ritz method. The proposed solutions are composed with classic solutions and are found to be in good agreement with the classical predictions. Thus the accuracy of the programs, i.e. the analytical solutions, is justified.In order to investigate the effects of different geometrical parameters and material properties on the deflections of the deck-girder-rib bridge system, numerical examples are analyzed in this section. The influence of the aspect ratio, the relative thickness and the relative length of the ribs are discussed and are compared with the classic solutions. It is found that the aspect ratio has a great influence on the deflection of deck. However, when the aspect ratio is big enough, the deflection of the deck does not change significantly. In addition, the stiffening ribs have a great influence on capability of the deck to resist the deformation. The anisotropy of the deck increases with the relative thickness. However, when the relative thickness is large enough, the anisotropy decreases with the increasing of the relative thickness and disappears completely after the relative thickness reaching the largest.Two finite element instances are built to compare with the proposed analysis. Similarities and differences between the proposed analysis and finite element are discussed in this section when stiffening of the main girders is finite or infinite. The analytical approach presented in this paper eliminates the very intricate and arduous kinematics study among deck-girder-rib and allows the bridge engineer to fast and convenient estimate the deformation in an orthotropic bridge deck.