Description

BRANZ research has found that the current requirements for the distribution of seismic bracing elements in NZS 3604:2011 Timber-framed buildings are too lenient. Full-scale experiments and three-dimensional modelling suggest that some parts of irregular light timber-framed (LTF) buildings could be unacceptably flexible during earthquakes, with lateral deflections up to five times greater than for regular LTF buildings. This would result in Code-compliant buildings experiencing damage during earthquakes that is uneconomical to repair.

New Zealand is unique internationally in considering plasterboard wall and ceiling linings to be structural elements of timber-framed buildings. These elements are also relied on as bracing to provide resistance against movement during seismic events.

Scope

In this report:

• International literature review on the seismic behaviour of irregular buildings
• New Zealand standard for seismic bracing in LTF buildings
• Modelling plasterboard wall performance
• Rigidity study of ceiling diaphragms
• Design of test buildings for three-dimensional seismic analyses
• Structural modelling and seismic analyses
• Key findings
• Recommendations
• Future work