Mechanical behavior of timber columns reinforced with high-performance bamboo-based composites and self-tapping screws under axial compression

This study investigated the mechanical properties of wood columns reinforced with high-performance bamboo- based composites (HPBBC) and self-tapping screws (STS) under axial compression. HPBBCs were fixed to the wood columns' surface by the STS to achieve a reinforced method that enlarges the cross-section. HPBBC, with high strength properties and stability, can provide sufficient load-bearing capacity and minimize materials usage. STS can form threads in wood to create a mechanical bite when screwed into wood materials, which firmly attach the HPBBC to the wooden column. Twelve full-size wooden columns strengthened by the reinforced method were fabricated and tested under axial loads. The research variables include cross-sectional shapes, reinforcement thicknesses, and reinforcement materials. Lateral deflection, longitudinal strain, displacement, and load were measured. The test results showed that STS could effectively fix the HPBBC to realize the reinforcement method. Enlarging the cross-section area of wood columns only by 18-60 % can increase the load-bearing capacity of wooden columns by 25-173 %. Meanwhile, the lateral deformation of the reinforced wooden column was reduced. The ratio between the spacing of the STSs and the thickness of reinforced materials was a key factor that allowed both materials to damage synergistically instead of local buckling of the reinforced panels. The reinforced materials with higher elastic modulus can provide better-reinforced effect. Finally, a load-bearing equation for an enlarged section of the wooden columns was derived and iterative calculated, and the calculated results are in good agreement with the test result.