Seismic assessment of existing buildings

The guidelines provide the assessment component of the earthquake-prone building regulations and EPB methodology that came into force on 1 July 2017. Version 1 of the guidelines must be used for all engineering assessments that territorial authorities use to decide whether or not a building is earthquake prone.

The guidelines provide methods for two levels of assessment. Initial Seismic Assessment (ISA) provides a broad indication of the likely level of seismic performance of a building. In some cases, an ISA will be followed by a more comprehensive Detailed Seismic Assessment (DSA).

Both assessment methods rate a building as a percentage of the new building standard applied to an equivalent new building on the same site. For assessment purposes, new building standard refers to the minimum life safety performance requirements of Building Code clause B1 – Structure.

Outline of the Engineering assessment guidelines

The guidelines have three distinct parts.

Part A – Assessment objectives and principles

Part A outlines the scope and application, and provides a general overview of the seismic assessment process. It describes the linkage with the relevant requirements of the Building Act 2004, associated regulations and the EPB methodology. 

Part B – Initial seismic assessment

Part B describes the Initial Seismic Assessment (ISA). The ISA provides a broad indication of the likely level of seismic performance of a building. In some cases, an ISA will be followed by a Detailed Seismic Assessment.

Part C – Detailed seismic assessment

Part C describes the Detailed Seismic Assessment (DSA). The DSA provides a more comprehensive assessment than an ISA. 

Part C is published in ten independent sections. Sections C1 to C4 collectively build on Part A and are to be used in conjunction with guidance for specific materials in Sections C5 to C10.

• Section C1 provides an overview to the DSA process. It explains the objectives and sets out key steps for an assessment at this level, including specific guidance on the calculation of an earthquake score in the context of a DSA.
• Section C2 sets out a DSA procedure. It specifies general analysis requirements including basic assumptions, selection of seismic analysis procedures, and the consideration of structural weaknesses.
• Section C3 explains how to determine the earthquake hazard and loading requirements used to assess the Ultimate Limit State (ULS) demand that relates the building capacity to the standard required for a new building.
• Section C4 provides guidance for considering geotechnical behaviour and its impact on the seismic behaviour and earthquake rating of existing buildings. This section includes guidance on the recommended interactions between structural engineers and geotechnical engineers and their particular roles and responsibilities.
• Sections C5 to C9 provide assessment methods for the specific construction materials of existing buildings:
• C5 – Concrete buildings
• C6 – Structural steel buildings
• C7 – Moment resisting frames with infill panels
• C8 – Unreinforced masonry (URM) buildings
• C9 – Timber buildings
• Section C10 gives specific recommendations for assessing Secondary Structural and Non-Structural (SSNS) building elements. The guidance in this section allows these elements to be rated either independently or in conjunction with an overall building assessment.

Templates

The Initial Evaluation Procedure (IEP) assessment template [ZIP 2.6MB] (note: this is a maco-enabled spreadsheet supplied in a ZIP file) provides working versions of tables IEP-1 to IEP-5.

The assessment summary report is used to summarise the key points from initial seismic assessments (Part B) and detailed seismic assessments (Part C) and must be included at the front of all engineering assessments for earthquake-prone buildings purposes.

Related information

• The methodology to identify earthquake-prone buildings (EPB methodology)
• Managing earthquake-prone buildings
• What you need to know: Section C5 'Concrete Buildings' proposed revision