Evaluation of bulk orthotropic properties of heavy plywood bridge decking

Abstract

This paper devises a method for modelling the bulk orthotropic properties of heavy plywood bridge decking described in Australia as Bridgewood, which can be customized in terms of the number of plies it consists of and also the direction of the grain for each ply to distribute its strength and stiffness characteristics laterally and longitudinally. Modelling plywood decking in finite element programs (FE) represents a problem, as an example a 166 mm deep plywood deck will contain approximately 50 × 3 mm thick single veneers that ideally should be represented individually in any complete bridge superstructure model. When taken over a 12 m span on a 3.2m wide bridge deck the FE model grows to an unmanageable size if element aspect ratios are to be held to no greater than 4 as recommended in Strand 7 (the FE software used). The size of the FE model was reduced whereby Bridgewood was treated as an orthotropic material with bulk elastic properties. A smaller model is used first in which the veneers are represented directly and specific loadings and support conditions applied that enable bulk elastic properties to be determined. To a limited extent, the bulk properties are then confirmed by laboratory testing.