Dowel-Bearing Strength of Southern Pine Cross-Laminated Timber

The current method for estimating parallel-to-grain dowel bearing strength of cross-laminated timber (CLT) fasteners applied perpendicular to the face in the US adjusts the length of the fastener to account for the effect of cross-layers rather than modifying the dowel bearing strength. This method is counter to more-commonly used methods in Canada and Europe which adjust the dowel bearing strength of the CLT material and using the original length of the dowel. Currently, there are no experimental data supporting the use of an adjusted fastener length. This paper presented an alternative method for CLT dowel bearing strength assessment according to the US design code. The proposed method produced similar or slightly conservative dowel bearing strength values compared with the current US design method. Experimental results of dowel bearing strength were compared against the current design code, the proposed method, and European and Canadian codes. Standard test procedures were used to evaluate, stiffness, yield strength, 5% offset yield strength and ultimate strength. Greater mechanical properties were found for CLTs containing more parallel-to-grain layers, whereas lower mechanical properties were found for CLTs containing more perpendicular-to-grain layers. The current US dowel bearing strength method, the proposed method, and the European design code produced similar results, which were slightly conservative compared with the experimental values. The proposed dowel bearing strength equation is felt to be an improvement given the ease of use and similarity in form to other design formats.