New Research by BRANZ Ltd Investigates Maximum Bracing Capacity

Bracing is an essential feature of any house to ensure it is built to stand up to the forces of nature.

A vital element of the overall house bracing system is bracing walls - walls that are specifically designed and built to resist the lateral forces that occur as a result of winds and earthquakes.

Over many years BRANZ Ltd has conducted a significant number of structural engineering research projects to find ways of making New Zealand homes safer. These research findings have helped with the development of documents such as New Zealand Standard NZS 3604 Timber Framed Buildings.

As part of this ongoing research programme, BRANZ has a project under way investigating the seismic performance of 'whole' houses. This is a project that will determine how all the parts of a house contribute to overall bracing performance.

One objective of this project was to determine the maximum strength of individual bracing walls for a typical house that was designed and built using NZS 3604.

Analysis of the initial results indicates that the strength of typical suspended timber floors to which bracing walls are connected may be less than previously thought.

On this basis, BRANZ decided that further investigation was warranted and an application for Building Research Levy funding to undertake additional research was approved by Building Research.

This new standalone project will thoroughly investigate maximum bracing capacity in homes.

The project started in July 2006 with thorough consultation with key industry stakeholders. The project as a whole is expected to be completed by the end of this year. The project results may lead to some re-commendations for changes to bracing detailing. The Department of Building and Housing and Standards New Zealand will be monitoring progress of the research project.

For further information in relation to this work please contact Greg Baker, BRANZ Ltd Manager of Fire and Structural Engineering.