Equivalent Strip Width for FRP Superstructure Design Using Timoshenko Beam Approximation

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This paper proposes the equivalent strip width for stiffness-driven design of fiber-reinforced polymer (FRP) superstructures in slab-type bridges. To calculate the deflections for design, this paper first presents a tractable and accurate analytical solution for FRP superstructures under certain symmetry in accordance with classical laminate plate theory. The equivalent strip width can then be obtained by equating beam flexural deflections to the analytical solution. Through the application of the equivalent strip width, two-dimensional FRP superstructures can be simplified as one-dimensional Timoshenko beams. In accordance with the parametric studies from finite-element analysis, Timoshenko beam approximation with the equivalent strip width can predict the deflections at points of interest in practical design with sufficient accuracy. At the design stage of FRP superstructures, several material and section properties required by typical plate analysis remain unknown to the designers. This paper shows that the simplified equivalent strip width with proper assumptions about a few key parameters can avoid this practical inconvenience and facilitate design. A procedure for the design of FRP superstructures is proposed and a design example is shown.