Background on AS1170.4 ‘Structural design actions, Part 4: Earthquake actions in Australia’

Throughout much of the past decade, our industry showed concern over Australia’s National Construction Code and the lack thereof in responsibilities over earthquake actions in newly built structures across Australia. The Queensland Building and Construction Commission published an article in 2019 titled ‘Designing and building to accommodate earthquake loads’ that highlights reasons why Australia must comply with the already existing earthquake standards AS1170.4 – originally published in 1993.

Australia sits on the Hikurangi tectonic plate boundary (a convergent boundary comprising of the Australian and Pacific plates which push against one another), and while we are not often subject to severe earthquakes, Australia is not immune to regular earthquake activity. Let us not forget about the 1989 earthquake in Newcastle which resulted in the tragic death of 13 people and saw more than 160 people injured.

To provide some context of recent quake activity, in 2020 Australia experienced 3,379 earthquakes – 153 of which measured over 5.0 magnitude.

I think this paint’s a picture as to why seismic compliance obligations must be enforced in the design of structural and non-structural components.

Hikurangi tectonic plate boundary Photo credit: Geonet

Hikurangi tectonic plate boundary

Newcastle Earthquake 1989

Newcastle Earthquake, 1989

Photo credit: GeoScience Australia, Australian Government

Historical earthquakes of Australia

Industry obligations

The aim for AS/NZS1170.4 in the event of an earthquake, is to prevent collapse and protect life. The structure must be able to absorb energy from the seismic activity and protect human life.

Buildings designed after the adoption of AS1170.4 in 1993 are believed to have adequate structural resistance for seismic loads. However, between 1993 and 2019, it was common for non-structural elements to have little-to-no earthquake resistance elements in their design.

From the accounts of survivors of earthquakes, we know that non-structural components have dislodged and caused injury, damage, or death.

what AS 1170.4 actually says

This Standard sets out procedures for determining earthquake actions and detailing requirements for structures and components to be used in the design of structures. It also includes requirements for domestic structures.

2.2 DESIGN PROCEDURE

The design procedure (see Figure 2.2) to be adopted for the design of a structure subject to this Standard shall-

( a) determine the importance level for the structure (AS/NZS 1170.0 and BCA);
(b) determine the probability factor (kp) and the hazard factor (Z) (see Section 3);
( c) determine if the structure complies with the definition for domestic structures (housing) given in Appendix A and whether it complies with the requirements therein;
(d) determine the site sub-soil class (see Section 4);
(e) determine the earthquake design category (EDC) from Table 2.1; and
(f) design the structure in accordance with the requirements for the EDC as set out in Section 5.

Importance level 1 structures are not required to be designed to this Standard, (i.e., for earthquake actions), and domestic structures (housing) that comply with the definition given in Appendix A and with the provisions of Appendix A are deemed to satisfy this Standard.

All other structures, including parts and components, are required to be designed for earthquake actions.

Source: AS 1170.4-2007 Structural Design Actions – Earthquake Actions in Australia, page 6, page 15.

What is required for non-structural elements?

Today, it is expected that non-structural components – such as mechanical plant equipment, HVAC platforms, ceilings, walls, plumbing and electrical work (such as lighting fixtures), have seismic capabilities built into their design and function. They must be able to withstand horizontal and vertical seismic forces.

The responsibility of ensuring compliance with AS/NZS 1170.4 sits with Principal building contractors and Certifiers.

Con-form Group’s Seismic Policy

At Con-form Group, we take the AS/NZS 1170.4 standard seriously. While we aren’t a Principal Builder, we are a Certifier.

We have engineered a seismic connection that secures our HVAC+R/mechanical plant platform systems to the structures they are installed on. Our proprietary seismic fixing is supplied with every project and DIY kit solution.

We also offer our clients the opportunity to obtain Seismic Certification written by our in-house team of Engineers, providing confidence and peace of mind.

Have questions about your seismic obligations? Contact our Team today.