Parameter study of an internal timber tension connection

Preliminary results from a project studying the behavior of a hidden timber tension connections are presented. The connection consists of a threaded steel rod inserted in a longitudinal hole along the central axis of a timber member, with a bearing plate and nut fitted on to the end of the rod in a specially cut mortise. This assembly was tested under pure axial load statically applied to the steel rod and the timber member. Observed failure modes are described and photographic documentation of failed connections is presented. Failure mode distribution is shown as a function of two physical parameters, the size of the bearing plate and the distance from the bearing plate to the end of the member, and a comparison is made with theoretical failure-mode domains derived from National Design Specification allowable stresses. The correlation of variations in the physical parameters with ultimate strength and ductility is also discussed. Initial results show the connection to be predictable, ductile, and potentially economical.