Damage to suspended ceilings from recent earthquakes has heightened the need for correct design and installation of ceilings and other non- structural parts of buildings. The failure of non- structural elements in an earthquake can seriously injure or even kill people and can prevent the use of buildings after an earthquake.
AWCI Suspended Ceiling Code of Practice for the New Zealand construction industry focuses on seismic restraints and separations for suspended ceilings and on the roles and responsibilities of those involved to ensure that suspended ceilings are designed and installed correctly.
For Design, Installation and Seismic Restraint of Suspended Ceilings
Options for the design of seismic restraints for Grid Suspended Ceilings include:
Option 1: Full seismic restraints design incorporated in building consent documentation and tender documents. This option is preferred to encourage fully conforming and untagged tenders, and to assure fully compliant ceiling installations.
Option 2: Generic Design Guides. New Zealand manufacturer/supplier Generic Design Guides provide seismic bracing installation details for basic ceilings within product limitations and structural performance assumptions, for subcontractor design and pricing. This option encourages fully conforming tenders generally limited to Category P.7 (AS/NZS 1170.5:2005 Table 8.1) ceilings to Serviceability Limit State (SLS1) (with limited ULS options also available). Option 2 tenders should identify the proposed bracing concept, the applicable Generic Design Guide, and any underlying design assumptions. Any ceilings outside the scope of Generic Design Guides (generally being greater than 30/40 metres above ground level, or where individual components weigh more than 10 kg and are able to fall more than 3 metres onto a publicly accessible area) should be nominated in the tender and identified for specific engineering design, and a Provisional Sum allowed for engineer-designed bracing as
Option 3. Unless otherwise stated in the ceiling contractor’s tender underlying assumptions include building importance level of 3 or less (AS/NZS 1170.0:2002 Table 3.2), relevant geographic location (AS/NZS 1170.5:2004 Table 3.3), annual probability of exceedance 1/25 (AS/NZS 1170.0:2002 Table 3.3), and adequate space and fixing provisions for installation of compliant seismic restraints. The main contractor or the client’s structural engineer should verify tenderers’ stated assumptions post-tender when full engineering data is available, and any required additional bracing should be a variation. Option 3: Specific engineering design. Specific engineering design (required where Option 1 does not apply, and Option 2 does not apply to some or all ceilings). Unless full engineering data has been provided within the tender documents such design must be carried out post-tender when full structural and building performance data is available. Where the scope of seismic bracing cannot be accurately ascertained at tender a Provisional Sum*2 should be nominated for the added cost of bracing.