Designing and building to accommodate earthquake loads

Compliance with relevant standards

Recent devastating earthquakes around the world should remind all building industry practitioners of the importance of ensuring that our buildings in Australia comply with the National Construction Code and Australian Standard AS1170.4 `Earthquake actions in Australia’.

Let’s not forget the fact that Australia has experienced the devastation caused by an earthquake on the morning of 28 December 1989 at Newcastle where 13 people were killed and more than 160 were hospitalised.   

Generally speaking, all buildings need to be designed and constructed in accordance with AS1170.4 unless they are not captured under its scope such as buildings that are:

  • domestic structures of class 1a or 1b that are 8.5m or less in height 
  • Importance Level 1 structures (e.g. farm buildings and sheds, isolated minor storage facilities, minor temporary facilities).

Non-structural components need to be considered

A common misconception in the building industry is that only the primary structural frame of a building needs to be considered for earthquake actions, this is not the case. Non-structural components of a building and their fastenings need to be designed for earthquake forces as required by AS1170.4.

Additionally, on multi-storey buildings ‘inter-storey drift’, which is the amount of potential movement that could occur between floor slabs above one another in any given storey of a building during an earthquake event, needs to be considered.

AS1170.4 Clause 8.1.4 provides a comprehensive list of architectural (non-structural) components that require consideration for earthquake loads being:

  • (i) Walls that are not part of the seismic-force-resisting system
  • (ii) Appendages, including parapets, gables, verandas, awnings, canopies, chimneys, roofing components (tiles, metal panels) containers and miscellaneous components
  • (iii) Connections (fasteners) for wall attachments, curtain walls, exterior non-loadbearing walls
  • (vi) Partitions
  • (v) Floors (including access floor systems, where the weight of the floor system shall be determined in accordance with clause 6.2.2
  • (vi) Ceilings
  • (vii) Architectural equipment including storage racks and library shelves with a height over 2.0m.

The Australian Standard also stipulates that a number of mechanical and electrical components and their fastenings commonly found in our high rise buildings also require consideration of their capacity to accommodate earthquake loads for example:

  • Lighting fixtures
  • Ducts, cabling and piping distribution systems
  • Fire suppression and sprinkler systems.
  • For a comprehensive listing of all components referenced by AS1170.4 which require consideration for earthquake loads please refer to the Australian Standard.

Responsibilities of principal building contractors

Principal building contractors are reminded that they are ultimately responsible for ensuring that the buildings they construct comply with the requirements of AS1170.4.

The QBCC recommends that principal building contractors ensure that all non-structural elements such as the architectural, mechanical and electrical components referred to above have been properly considered for earthquake loads in their design through to installation on-site.

It may be beneficial to request the structural design engineer of a  building to provide details such as effective floor acceleration and the allowances for inter-storey drift to system manufacturers of architectural, electrical and mechanical components to ensure the selected systems have the required performance characteristics to accommodate the expected earthquake actions. 

Responsibilities of certifiers

Building certifiers are also reminded of their responsibilities to ensure the compliance of such components with the National Construction Code. 

In Queensland, to evidence compliance, building certifiers would normally require Form 15 design certificates and Form 16 installation certificates to be completed, identifying the components covered with appropriate referencing to AS1170.4, by suitably qualified design professionals and installers. 

History has proven around the world that many people can be injured or trapped in buildings affected by earthquake when non-structural components such as suspended ceilings, light fittings, walls and partitions and the like dislodge or collapse.

Queenslanders have the right to feel safe in all buildings where they live, work or play. Accordingly, the QBCC will pay particular attention to new building projects to ensure that designers, engineers, building contractors and building certifiers comply with the requirements of AS1170.4 where applicable. 

The Australian Building Codes Board (ABCB) has also recently posted an article on this topic.