Experimental research on wood beams strengthened with engineered bamboo laminates attached with self-tapping screws

An experimental study of the flexural performance of heavy timber beams strengthened using self-tapping screw-affixed engineered bamboo materials is presented. Twelve larch beams were tested under monotonic loading to failure; these were reinforced on their soffits with either laminated bamboo or bamboo scrimber plates. In lieu of adhesive bonding, self-tapping screws with different diameters, lengths and layouts were drilled in the bamboo plates and the beams to transfer bond forces across the interface. Flexure failure modes including wood crushing and wood fracture failure were observed for most beams. The ultimate failure mode of beams strengthened using bamboo plates was a combination of longitudinal splitting and transverse fracture of the plates. Through service level deflections, the strengthening bamboo plates improved the beam stiffness and showed no indication of relative slip along the wood-bamboo interface. At higher loads, and approaching ultimate capacity, the laminated bamboo tends to split, resulting in slip at the strengthening interface. The highly anisotropic laminated bamboo did not perform as well as the more orthotropic bamboo scrimber. The latter better resisted splitting. The mechanical jointed beam model was shown to provide a good estimate of strengthened beam moment capacity.