Seismic
AS 1170.4-2007: Structural Design Actions Part 4: Earthquake actions in Australia requires earthquake loads on both structural and non-structural components to be considered in the design of all buildings in Australia.
The term ‘non-structural’ includes (but is not limited to) suspended ceilings, partitions, services, etc.
Table B1.2a of the NCC explains the Importance Level of the building based on the type and purpose.
| Importance Level | Building Type | Example |
|---|---|---|
|
1 |
Buildings or structures presenting a low degree of hazard to life and other property in the case of failure |
Farm buildings, minor storage facilities |
|
2 |
Buildings or structures that are designed to contain a large number of people |
Low rise residential construction |
|
3 |
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 |
|
4 |
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 |
Only ‘Importance Level 1’ structures may not require consideration – here are some examples:
- Residential dwellings less than 16m wide and 8.5m high to top of roof
- Garden/storage sheds
- Carports
If the structure doesn’t resemble something like the above, consideration is required to design and install the non-structural elements to comply with AS 1170.4-2007.
Design Considerations
It’s important to factor seismic engineering into the cost of designing and/or installing the ceiling system and to get this process started as soon as possible.
The cost of engineering can vary significantly depending on the size of the project and the complexity of the systems being installed.
AMF Ceilings distributors can offer the services of a third-party engineering consultant for ceilings only, provided AMF systems are being installed. Alternatively, an engineering consultant can be engaged by the customer. Once the seismic design is complete, a document should be provided explaining how to brace the ceilings, detailing perimeter-bracing (fix/float) or plenum-bracing.
Installation Considerations
It’s also important to be aware of how the ceiling will need to be installed and which components are required prior to beginning installation.
The perimeter-bracing (fix/float) method involves having two perpendicular ceiling perimeters mechanically and rigidly fixed to the walls and the alternate perimeters facilitating movement, using perimeter clips. The lateral seismic load would be transferred to the fixed perimeters, so the walls will need to be designed to take the specified lateral load.
The plenum-bracing method involves having 45 degree bracing from the grid up to the underside of the structure. The lateral seismic load would be transferred through the braces up to the underside of the structure. Perimeter clips are still required with this method however, they will all be installed as ‘floating’ perimeters.
Which method is specified in the seismic design will depend on many factors such as soil type, structure height, ceiling weight, the suspension system, the size of the area, etc.
Contact AMF Ceilings or an AMF Ceilings Distributor for more information.
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