Low-Rise Buildings Guideline – Stage 1 Review

Abstract

The seismic assessment of low-rise buildings is an important area of seismic assessment in New Zealand given the prevalence of these types of structures, especially outside the main centres. The Joint Committee for the Seismic Assessment of Existing Buildings (JCSAEB) convened by Ministry of Business Innovation and Employment (MBIE) with members from the technical societies and Toka Tū Ake EQC has identified that in many instances seismic assessments of low-rise buildings typically constructed with steel portal frames, reinforced masonry, tilt-slab walls or timber framing with lightweight flexible diaphragms are resulting in unrealistically low ratings (<34%NBS). This is often due to a lack of readily identifiable and reliable load paths which means an assessment to the current guidelines can result in a low score. However, anecdotal evidence from past earthquakes suggests these types of structures will generally perform well despite an apparent lack of a defined load path. To address this issue the MBIE has commissioned Stage 1 of a project to investigate the issue in more detail and recommend next steps for providing engineers with updated guidelines/procedures to allow more appropriate ratings to be assessed for this building typology. This paper will summarise the findings of stage 1 and what the recommendations are for future stages.