Use of fibre reinforced polymer (FRP) in column applications is increased because it can act as a confining material, a reinforcement and a structural column. The application of FRP tubes is correlated with the fibre orientation since tube stiffness is mainly attributed to the stiffness of fibres. Thus, for confinement, the fibres should align in the transverse direction of the tube while they should align in the axial direction when tubes are used as compression members. FRP tubes with fibres mainly in axial direction may reach failure because the stiffness in the perpendicular direction to fibres depends only on the stiffness of the matrix. In order to boost the stiffness in the secondary direction while supporting fibres in the main direction, fibres should be in multi-directions. This paper reviews and identifies gaps in knowledge on the use of FRP materials in column applications in new or existing construction regimes.

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As the axial behaviour of hollow pultruded fibre reinforced polymer (PFRP) profiles is governed by the instability conditions due to the local and global buckling, the determination of the safe load carrying capacity of FRP columns is vital. The compressive performance of PFRP tube depends on many factors such as fibre type, fibre content, and orientation of fibre layers, cross-section, thickness and height of the column member. In this study, concentric compressive testing was conducted using PFRP short columns. Based on the fibre orientation and thickness, the samples were divided into two groups of tubes in a square shape and two groups in a circular shape. The height of columns is designed to keep the slenderness ratio (length/lateral dimension) of 5. The axial behaviour of FRP columns was simulated using STRAND7 finite element software package. The laminate method was followed to define the mechanical properties of the FRP material. Failure was investigated by using the Tsai-Wu failure criterion. The experimental results show that the failure mode of the hollow square tube was either local buckling or corner splitting at the mid-height followed by buckling. Although both types of circular tubes failed in a similar way by crushing one end with high noise, followed by separation of the crushed end into strips, the stiffness and the load capacity of PFRP column was higher for the profiles with fibres oriented close to the axial direction. The numerical results are in close agreement with the peak value of the experimental results. This can be extended to study the effects of all factors that influence the axial behaviour of PFRP columns numerically.