The aim of this project was to validate the assumption used within the Australian Standard AS1720.1 for calculating compression perpendicular to grain for common timber species and develop practical methods to reduce compression deformation.
The project was successful in demonstrating that perpendicular to grain displacement of wall plates by studs can be reduced. It found that stud on stud connection was the best method as it removed the wall plates out of the load path altogether. The study also found where this is not possible, replacement of the wall plate with a stiffer timber such as a high density hardwood, softwood or cross laminated timber reduces this deformation.
The investigation also found that the method used in AS1720.1 to assign perpendicular to grain bearing capacities for various timber species by “strength group” or stress grade over predicted low to medium density timber species whilst under predicting high density timber species. Accordingly, it is recommended that perpendicular to grain bearing capacity be assigned by the timber species’ density and that the characteristic values of commonly used timber species be re-established.