This paper introduces a new, structural wood-concrete composite system. The system is formed by joining a wood component, such as a floor beam or laminated plate, to a concrete slab utilizing a continuous steel mesh of which one half is glued into a slot in the wood while the other half is embedded into the concrete. Two series of tests were performed and are presented: static push-out tests ͑to establish shear properties of the connector͒ and a full scale bending test with a span of approximately 10 m. Test results reveal that the steel mesh performs favorably-as a stiff yet ductile shear connector between the wood and the concrete. Design equations, per European standards ͑in absence of North American standards͒ are described and used to predict the failure load of the bending test. Calculations indicate that the tested beam performs with near full composite action-specifically, 97% effective stiffness and 99% strength of that of a beam with full composite action. This is a marked improvement in the efficiency of wood-concrete systems developed to date. The system shows itself to be superior to alternative systems in its high structural efficiency as well as being relatively easy to install and economic.
The ASTM D5764 standard, Standard Test Method for Evaluating Dowel-Bearing Strength of Wood and Wood-Based Products, for testing dowel connections provides a procedure for measuring the dowel bearing strength of wood and wood-based products. Laminated veneer bamboo (LVB) is a new building product that is employed in similar sizes and applications as dimensional lumber. Being new, more research is needed to understand the key factors and fundamental failure mechanisms that occur in LVB dowel connections to help ensure safe standards for further LVB product adoption and design. This study develops three-dimensional bilinear finite element models for half- and full-hole specimens in accordance with ASTM D5764 when loaded in compression parallel to the grain. The models simulate LVB fracture initiation due to shear stresses in the dowel joint by incorporating frictional stresses in the contact region between a steel bolt and LVB. The model also predicts displacement at failure, which is validated through comparison with experimental results: the material fails at 1 and 1.18 mm displacement loading parallel to the grain for half- and full-hole specimens, respectively. It is found that, despite the higher load-bearing capacity (strength) of the half-hole specimen, both specimens fail at approximately the same displacement because of in-plane shear stresses. This article clarifies the complex interactive state of in-plane shear, tension perpendicular to the grain, and compression parallel-to-grain stresses using the Tsai–Wu failure criterion in the critical zone beneath the bolt hole for half- and full-hole specimens. These findings suggest that care should be taken to select a test method that captures the performance of LVB dowel joints because of different failure mechanisms that occur for full- and half-hole specimens.
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