Expedient moment connections for timber portal frame buildings

Abstract

This thesis introduces an expedient semi-rigid moment connection, the Quick Connect, for use in timber portal frames. The connection is rod based, with components which have easily determinable attributes. Connection components are sized by means of a simple design methodology which has been verified in this thesis by comparison to full scale test results. The design methodology applies straightforward capacity and deflection relationships which are gained from either design standards or from first principles. The fully threaded self-tapping screw capacity and slip values are the only exception. These have been determined by testing. Due to the inherent simplicity of the connection, it is adaptable for use as a column base, knee, splice and apex connection. The use of the connection is not limited to pure timber structures, use in hybrid timber-steel and timber-concrete structures is possible. The majority of the connection componentry can be assembled by an offsite fabricator. This assembly approach is comparable to that used when building in steel. This allows expedient assembly of the joint onsite once portions of the structure or individual members have been lifted into place. This approach reduces the number of crane hours and onsite labour required. Fabrication offsite is a deviation from the traditional approach of erecting timber building whereby all assembly and erection work was completed onsite. As a result, a significant reduction in build cost and critical construction path times can be achieved. The connection does not constrain the member size. Undesirable characteristics such as perpendicular to the grain stresses are avoided by design. It is possible to size the connection in two ways. The designer can take an iterative approach, whereby the connection components are optimized for the applied loads. Alternatively, standard connection sizes can be determined which are calculated to withstand the portal member characteristic design values. Both approaches yield a ductile connection whereby the main rods are designed to act as an accurately definable failure mechanism.