This report presents the results of a pilot study of the equilibrium moisture content and tensile strength of 20.5 mm thick Canadian Softwood Plywood and 15.9 mm thick waferboard exposed to a range of climatic conditions. Plywood and waferboard were conditioned until they reached constant weight at 20 C/65%RH and 5 C/90%RH. In addition some of the plywood and waferboard test specimens conditioned at high humidity subsequently were moved to a 20 C/65%RH atmosphere where they remained until an equilibrium moisture content had been achieved. A fourth group of plywood and waferboard specimens were kept at ambient conditions in the laboratory. Additional groups of plywood specimens were conditioned at 20 C/50%RH, 20 C/80%RH and also reconditioned from wet to 20 C/50%RH. Density, moisture content and tensile strength of all specimens were determined after they had reached equilibrium moisture content. The results indicate that there can be large differences in the equilibrium moisture content of wood-based panel products. The results also indicate a strong moisture dependency for the tensile strength of waferboard. No clear trend for the tensile strength of plywood in relation to moisture content could be established by this study.
A literature survey on experimental data and analytical studies of the structural behaviour of wood framed shear walls and diaphragms has been carried out. The utility of various analytical methods for the study of internal forces in these structural elements due to external static or dynamic forces has been noted. It also has been concluded that the complexity of these analytical methods precludes their use as a tool for standard designs on a daily basis. For these standard designs currently established design methods will likely be continued to be used for some time. Establishment of design data by means of testing for panel thicknesses currently not included in the Canadian design code is recommended.
The objective is to broaden the market for sheathing panels by establishing shear strength values for the design of floor and roof diaphragms using 18.5mm and 20.5mm thick plywood panels. As a result of an emergency no work was done on this project.
