27 June 2019
With the QBCC recently carrying out site audits focusing on the Earthquake Standard and compliance with Section 8 – non-structural parts and components, it has never been more important for builders to understand their obligations.
The NCC requires all buildings to comply (to varying degrees) with AS 1170.4-2007: Structural Design Actions Part 4: Earthquake actions in Australia (the Earthquake Standard). This requires earthquake loads on both structural and non-structural parts and components to be considered in the design of all buildings in Australia.
Engineers, architects, designers, building certifiers, manufacturers, installers, and builders all share responsibility to comply with the Earthquake Standard.
Recently, state regulators and the ABCB issued communication to industry stakeholders reminding them of their obligations to comply with the Earthquake Standard particularly Section 8 (non-structural parts and components).
The QBCC has also recently started to carry out site audits for compliance with the Earthquake Standard focusing on Section 8 Design of Parts and Components. Certifiers are now requiring evidence of suitability of the building products used and design and construction certificates (i.e. Forms 15 and 16) to confirm compliance of the structural and the non-structural parts and components with the Earthquake Standard.
You can read more on the specifics of earthquake design and what is involved below, as well as what you must do to ensure the manufacturers you use can produce the documentary evidence needed to show that their material, product, form of construction, or design meet the requirements.
To address some of the issues recently highlighted during the audits, key industry manufacturers and suppliers are currently preparing documentation that confirms the loads that their products comply with. This will assist builders with establishing evidence of suitability (Forms 15 and 16).
Master Builders is pushing for changes to the Earthquake Standard, for example, modifying earthquake provisions in particular locations. We would like to see zones where the Earthquake Standard does not apply like the cyclonic wind design requirements.
If you require further information regarding how to ensure you are complying, our Technical team are on standby to assist. Call us on 1300 30 50 10 or email our Technical team for member-exclusive advice.
What is involved with earthquake design?
While consideration must be given to the Earthquake Standard for every building constructed in Australia, the design actions are not the same for all buildings. There are a number of factors that must be considered when determining the design loading that applies.
The factors include:
- Location of the site to determine the Hazard Design Factor (see Figure 3.2(F) AS1170.4);
- Importance level of the building – Levels 1 to 4 (see NCC B1.2 Tables B1.2a and B1.2b);
- Site Sub-Soil classification – Class Ae, Be, Ce, De, Ee (see Section 4 AS1170.4); and
- Structure height.
Earthquake design categories
Based on these factors, the Earthquake design category (EDC) can be determined (see Table 2.1 AS1170.4). There are three different Earthquake Design Categories and the design requirements are different for each of these categories. A structural engineer must be engaged to determine which EDC applies to the building.
Table 2.1 of AS1170.4-2007
Figure 3.2(F) of AS1170.4 provides the Hazard Design Factor for various areas of Queensland with the majority of Queensland having a low design factor of less than 0.08. However, higher zones have been identified for areas from Noosa to Rockhampton (inland to approx. Taroom) and around Bowen. There is also now a minimum design factor that applies to all areas (0.08).
The Importance Level of the building will depend on the type and purpose of the building being constructed. This is covered by Table B1.2a of the NCC as noted below (along with examples):
Buildings or structures presenting a low degree of hazard to life and other property in the case of failure
Farm buildings, minor storage facilities
Buildings or structures not included in Importance Levels 1, 3 and 4
Low rise residential construction
Buildings or structures that are designed to contain a large number of people
Buildings and facilities where more than 300 people can congregate in one area, schools with more than 250 people
Buildings or structures that are essential to post-disaster recovery or associated with hazardous facilities
Post-disaster emergency centres or shelters, buildings and facilities containing hazardous conditions that extend beyond property boundaries
For Class 1a and 1b houses that fall within the requirements of a ‘domestic structure’ in Appendix A to AS1170.4 – 2007 (i.e. less than 16m wide and 8.5m high to top of roof), it is unlikely that special design loadings will apply provided the design of the home complies with all other applicable design standards such as AS1684 and good building practice.
However, additional earthquake design requirements will apply for some material types such as rammed earth walls. Additional design requirements also apply to houses in areas with higher Hazard Zone Factors.
For houses that exceed the dimensions of a ‘domestic structure’, they are to be designed as a building with Importance Level 2.
The Earthquake Standard specifies different design loads to be resisted depending on the EDC and height of the building and a different method of analysis to determine those loads. However, a simplified static design may be used for buildings up to 15m high with Importance Level 2 and EDC II.
While the Earthquake Standard applies to all buildings, it is expected that the wind design on the structure of most buildings in Queensland will exceed the minimum earthquake design loads. However, an issue is likely to arise with respect to the minimum earthquake design loads on non-structural parts and components which are not typically considered in wind design.
The Earthquake Standard requires these elements of a building (e.g. partitions, ceilings, mechanical and electrical components and fixings) to also resist certain earthquake loads as failure of these elements can result in significant damage to the building and its occupants during an earthquake. Section 8 of the Earthquake Standard provides a full list of the non-structural parts and components that must be considered.
It is imperative that contractors and designers ensure that all buildings comply with the requirements of the Earthquake Standard. In particular, seismic design and detailing of non-structural partition installation documentation should be collated and prepared at the beginning of the building development approval process and prior to the development approval being issued.
Contractors should also ensure that product manufacturers can produce the documentary evidence needed to show that their material, product, form of construction, or design meet the requirements of the Earthquake Standard.
It is also strongly recommended that a structural engineer be engaged early for both the building’s structural design and the seismic design of non-structural parts and components as a design certificate will be required to certify compliance with the Earthquake Standard and the NCC.