Moment Resistance Performance of Dowel Based Connections in Wood Products

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The moment resistance of bolted connections in wood is poor due to the low tension perpendicular to grain and longitudinal shear strengths of wood. As a practical solution designers may sometimes consider such connections as pinned to only carry shear and axial forces and ignore their moment carrying capacity. The problem is that the wood does not know that it is not supposed to carry moment and could perform poorly even under the intended loading. Alternatively, very slender bolts/dowels can be used with large spacing and end distances which may not be very economical. Rational design guidance is needed to allow bolted moment connection to be used efficiently and safely. The fundamental problem is that the interacting effect of shear and tension perpendicular stresses is not well understood for wood and modern wood products. Both modes of failure are brittle in nature and as a natural material the strength properties of wood are nonhomogeneous and random. These features lead to the fact that tensile perpendicular to grain and longitudinal shear strengths are both sensitive to stressed volume. The larger the stressed volume, the lower the strength. Comprehensive data is not available on the effect of stressed volume on these interacting stresses. Furthermore, the influence of reverse cyclic loading on these strength properties as in the case of demands from earthquakes have not been fully studied.****The proposed work will study the moment carrying capacity of bolted moment connections under monotonic and reverse cyclic loading as components and in structural frames. The interacting brittle failure mode of tension perpendicular to grain and shear will be studied with consideration of stressed volume effect. This information will lead to design guidance for effective reinforcement techniques. Finally, reliability based design procedures will be developed to qualify their performance to handle demands from both seismic and non-seismic loading. The expected impact of the study is more rational design procedures for consideration of bolted and dowel based moment connections leading to safer and more cost efficient design solutions using generic non-proprietary based connectors. Successful implementation of the results will lead to better and safer wood-based buildings especially for the bigger and taller wood building market.