SR337 Design guidance of specifically designed bracing systems in light timber-framed residential buildings (2015)

The objective of this study was to develop design guidance to mitigate, through better designing and detailing, the earthquake damage to light timber-framed (LTF) residential buildings.

The construction practice and engineering characteristics of mainly LTF residential buildings were examined first. The examination highlighted that potential stiffness incompatibility between conventional LTF bracing walls and specifically designed bracing elements could significantly facilitate earthquake damage to LTF buildings. In order to achieve stiffness compatibility between specific bracing elements and LTF wall bracing elements, the expected seismic performance level of LTF residential buildings with minimum NZS 3604 seismic bracing was assessed. The assessment was conducted, based on a displacement-based approach and available P21 test results of sheathed LTF walls.

The assessment revealed that the displacement performance achievement of the building system with minimum NZS 3604 seismic bracing is inappropriate for use as the performance criterion for specifically designed seismic bracing elements. The seismic performance requirement for specifically designed seismic bracing elements in mainly NZS 3604 buildings was established as 1%, in terms of storey drift at ultimate limit state. This was based on observed test results of conventional LTF bracing walls and the current seismic loading standard NZS 1170.5. A step-by-step seismic design procedure for specifically designed bracing elements, which was developed according to a displacement-based approach, is presented.