Structural behaviour of hybrid FRP pultruded columns. Part 2: Numerical study

Abstract

The structural behaviour of hybrid fibre reinforced polymer (FRP) pultruded members under concentric compression is studied in this paper (Part 2) through the use of numerical models – the experimental characterisation was presented in preceding paper (Part 1, Nunes et al., 2015). The hybridization of glass-FRP (GFRP) profiles is made through the partial replacement of the glass reinforcement with (stiffer) carbon fibres. First, a brief literature review shows the absence of available finite element (FE) models that take into account all the nonlinearities (material and geometrical) that influence the FRP column behaviour, and indicates the need to develop reliable and consistent models. Then, the FE model developed in this paper is described in detail. The elastic buckling behaviour of the columns tested in Part 1, with similar I-section shape but different configurations of carbon fibre reinforcement and different lengths, is evaluated. Three failure criteria for composite materials (Maximum Stress, Tsai–Hill and Hashin) are presented, implemented and their differences discussed. Using the Hashin criterion associated with a material damage model, progressive failure analyses were performed to simulate the nonlinear behaviour and failure of the hybrid columns. The numerical results comprise load–displacement curves, ultimate loads, stress–strain curves and failure modes, which are validated by comparison with the experimental results. Finally, the available design procedures for FRP columns are critically reviewed and applied to evaluate the columns’ ultimate loads. In this regard, it is shown that buckling prevails over material strength and that existing standards do not predict accurately the ultimate load of short columns or laterally braced columns.