Seismic Bracing

Bracing Checklist
Those involved in the interior fit out industry know how difficult it has been to comply with building code requirements and ceiling manufacturers warranties.

For decades the manufacturers of two-way ceiling grid have stated that no materials should be connected to their product – for decades this requirement has been largely ignored.

However, there is a proprietary bracing system that is easy to install, is cost effective and complies with building code requirement and ceiling manufacturers warranties.

Let’s look at how all the parts of an interior fit out project come into play and how they relate to bracing.

Ceiling Grid
Ceiling grid is designed to carry its own weight, measured at approximately 15kg/m2 or less. Attachment of a partition wall or glazing line to a suspended ceiling will exceed this weight, and restrict the ceiling grids design performance. Remember, partition walls weigh 40kg/m2 or more, while the glass from glazing lines weighs in at approximately 25kg/m2.

In addition to this, the ability of the ceiling grid to support itself during a seismic event is grossly compromised when walls are connected against the manufacturers specification. Walls connected to the two-way grid will cause the two-way grid to fail, resulting in significant damage.

Partition walls and glazing lines need to be braced at all times, at a minimum of 40kg/m2 these walls have the weight to create catastrophic failure when horizontal deflection occurs.

Partition Walls
Bracing needs to allow for horizontal deflection of up to 40mm each way, while allowing for inter-story drift of 50mm. There is also a need for 90mm of in-plane deflection, which is required when the floating head of the partition wall moves in line with the wall.

Although vertical deflection is taken up in the construction of the wall itself, there are some projects where the
connection, to widely spaced C purlin top floor roof structures, additional vertical deflection may be required.

Service Clashes
The improvement in the co-ordination of service trades continues and as early collaboration improves, service clashes will be greatly reduced.

Bracing of walls, ceilings and services need to be considered early in the design and construction process to allow efficient sequencing on site.

Using a bracing system that provides for flexibility, in terms of bracing angle and direction or placement can allow partition installers to mitigate most service clashes.

What the Building Code Says
Turning to the building code for guidance on what is required for bracing best practice, we find Clause B1 Structure, B2 Durability, F2 Hazardous Materials and other cross over codes.

These outline what is required to properly brace nonstructural items, clause B1 specifically states the need to safeguard people from injury, loss of amenity and protect other property from damage caused by structural behavior
or failure.

Then parts loading can be found in AS/NZS1170, giving you the minimum requirements for a robust bracing system.
Take into account wind loadings, snow loadings and earthquake parameters (SLS and ULS) and you have the parameters for a bracing system that performs.

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