Modeling and application of thin-walled composite beams in bending and torsion.

摘要

Due to their favorable properties, pultruded fiber reinforced plastic (FRP) composite beams and columns are increasingly finding their way into infrastructure applications. In order for the structural applications of FRP members to be successful, engineering design analysis procedures are needed to accurately model such advanced materials and systems. Nonclassical effects such as shear lag, shear deformations, warping, torsion, and elastic couplings need to be included in the modeling of FRP composite structural members.;In this research, we address the analytical/experimental modeling of thin-walled open and closed composite sections in bending and torsion. Micro/macro-mechanics models are investigated to allow the modeling of pultruded composite sections. The lamina, laminate, and beam stiffness properties are predicted. The laminate stiffnesses are verified by coupon tests in tension and torsion, and the beam stiffnesses are verified by 3-point, 4-point, and cantilever bending tests.;The harmonic analysis technique of beams is used to develop a shear lag model for open and closed composite beam sections. The model predicts the nonuniform distribution of strains (shear lag) in FRP sections, and the analytical model is correlated with experimental and finite element results. The shear lag model is used to evaluate an effective bending stiffness to account for the nonlinear distribution of strains in the flanges of the FRP sections.;In this study, a Vlasov-type linear theory is developed to predict the torsional response of open and closed thin-walled composite sections; the theory includes elastic couplings such as torsion-bending coupling. In order to validate the analytical model, two FRP box sections are tested under double tip torsional loads, and their responses in terms of angle of twist and shear strains are recorded.;Also in this study, a design-oriented first-order shear deformation macro-flexibility (SDMF) model for the analysis of cellular FRP bridge decks consisting of contiguous thin-walled box sections is presented. The study includes analytical modeling of FRP deck-and-stringer short-span bridges, which can be used for new structures or replacement of deteriorating highway bridge superstructures.