Novel engineered wood and bamboo composites for structural applications: State-of-art of manufacturing technology and mechanical performance evaluation

Timber has been a popular building material for centuries and offers significant sustainable credentials, high mechanical and durability properties. Availability, ease to use, convenience and economy have made timber the most used construction material in history but, as it is a natural material, uncertainty in its mechanical characteristics is considerably higher than man-made structural materials. National codes and engineers usually employ high factor of safety to incorporate timber strength uncertainty in design of new structures and reinforcement of existing ones. This paper presents the results of 221 bending tests carried out on unreinforced and reinforced soft- and hardwood beams (fir and oakwood) and illustrates the reinforcement effect on timber capacity and strength uncertainty. Both firwood and oakwood beams have been tested in flexure before and after the application of a composite reinforcement made of FRP (Fiber Reinforced Polymer) unidirectional sheet. The uncertainty in the strength of reinforced timber is also quantified and modelled. Test results show that the FRP reinforcement is effective for both enhancing the beam load-carrying capacity and for reducing strength uncertainties.

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Uncertainty analysis of FRP reinforced timber beams

Engineered bamboo, produced through the technique of gluing and reconstituting, has better mechanical properties than round bamboo and some wood products. This paper studies the flexural performance of laminated beams produced with timber and engineered bamboo. The six-layer beams were made from Douglas fir, spruce, bamboo scrimber and laminated bamboo, or a combination of these. It is confirmed that glued-laminated wood beams produced with wood of weak strength, like spruce, can be strengthened by gluing engineered bamboo lumbers on the outer faces, thus achieving better utilization of the fast growing economic wood species. Flexural failure of the laminated beams was primarily triggered by tensile fracture of the bottom fiber in mid-span, followed by horizontal tearing beside the broken surface. No relative slip between layers was observed before failure, therefore the flexural capacity of the laminated beams can be predicted using equilibrium and compatibility conditions according to the plane section assumption.

Shijun Zhu

Papers

Flexural behavior of FRP and steel reinforced glulam beams: experimental and theoretical evaluation.

Local bond stress-slip relationships between glue laminated timber and epoxy bonded-in GFRP rod