Modeling of timber beams strengthened with various CFRP composites

Abstract

This paper presents a modeling approach to predict the behavior of timber beams strengthened with carbon fiber reinforced polymer (CFRP) composites. A three-dimensional finite element analysis (FEA) model is formulated, based on the orthotropic constitutive characteristics of timber species. The model provides the load–displacement relationship, strain development, stress concentration, and failure modes of the CFRP-strengthened timber beams and those responses are compared to the experimental data. The validated models are used for a parametric study to further examine the effect of various CFRP properties on the behavior of five timber species: Douglas Fir, Yellow Birch, Sitka Spruce, Yellow Poplar, and Northern White Cedar that cover most of the engineering properties available in practice. The strengthened beams show improved load-carrying capacity and energy absorption capacity when compared to unstrengthened counterparts. An optimal CFRP-reinforcement ratio is found beyond which no strength increase is achieved. Even though the elastic modulus of the CFRP composites influences the failure mode of the strengthened beams, it may not significantly affect the strength-increase of the beams because the properties of timber species are a dominant factor influencing the failure of the beams, rather than the CFRP properties.