Homogenization of a Composite, Multi-Girder Bridge Deck as an Equivalent Orthotropic Plate

Most bridge decks are orthotropic, because of the orthotropic nature of their component parts (e.g. isotropic slabs, grillages, T-beam bridge decks, multi-beam bridge decks, multi-cell boxbeam bridge, and slabs stiffened with ribs of box section). Thus, the orthotropic plate theory plays an important role in the static and dynamic analysis of bridges. For example, a multicellular Fiber Reinforced Polymer (FRP) composite bridge deck can be modeled as an orthotropic plate with equivalent stiffnesses that account for the size, shape, and constituent materials of the cellular deck. Thus, the complexity of material anisotropy of the panels and orthotropic structure of the deck system can be reduced to an equivalent orthotropic plate with global elastic properties in two orthogonal directions – parallel and transverse to the longitudinal axis of the deck cell. This paper investigates a homogenization of composite, orthotropic, three-span, multi-girder bridge to explore the concept of the volumetric and mass fractions of a reinforced composite material. This homogenization takes into account all properties of this composite structure (deck slab, girders and diaphragms). From those, all the equivalent orthotropic plate properties were obtained. The work is highly relevant with respect to evaluating the dynamic interaction between bridges and vehicles.