Experimental investigation of the compressive behaviour of GFRP wrapped spruce-pine-fir square timber columns

Abstract

An experimental program investigating the behaviour of square timber columns wrapped with fibre-reinforced polymer (FRP) composites under compression loading was undertaken. A total of six unwrapped control specimens and thirty glass FRP (GFRP) specimens were tested with emphasis on characterizing the altered stress–strain behaviour and examining the failure modes. The effects of varying GFRP composite configurations (fibre direction, thickness) were investigated, and each specimen was dissected after testing to study how the wood failed. Test results showed that with proper thickness, FRP wrapping can prevent undesirable splitting and shearing modes of failure in the wood and negate the influence of naturally occurring wood defects to induce crushing in the wood fibres. The crushing mode of failure promoted by FRP wrapping contributed to significantly improved post-peak behaviour with FRP wrapped specimens sustaining up to 61% of their peak compressive strength at a strain of 0.04 mm/mm compared to 41% in the control specimens. The reinforced specimens were on average capable of dissipating between 1.35 and 1.68 times more energy compared to the control group. It is clear from the test results that FRP wrapping can help the overall behaviour of wood members become more reliable and uniform. In particular, the consistency in the post-peak stress–strain behaviour and wood failure is conducive to the development of an analytical model. The improved post-peak behaviour could also benefit wood members in flexure and wood structures subjected to extreme loads such as earthquakes and blast loads.