USG ceilings Seismic design details

Our ceilings are designed using the USG Generic seimic design guide and has the following assumptions and limitations:

Building in which ceiling is installed

• Building must be located within New Zealand
• Building must be no more than 40 metres tall
• Building must not be Building Importance Level 4 having special requirements for "post-disaster" functionality (eg. some hospital areas, police station) - refer to AS/NZS 1170.b for full definition
• For perimeter fixed ceilings, a continuous nogging must be provided at the same level as the perimeter angle trim along all fixed edges of the ceiling (a continuous concrete or block masonry wall/beam is also acceptable)
• The support structure (including nogging, associated wall/bulkhead, and building superstructure) must be strong and stiff enough to carry the seismic bracing loads from the ceiling without suffering any damage. This must be confirmed by a Qualified structural engineer

Ceiling & Services

• Main Tees must be either: DONN DX30D, DXL38D, QX38D, DXT30D, DXT38D
• Cross Tees must be either: DONN DX30M, DX30D, DX38D, DXT30D, DXT38D
• Rivet strengths allow for use with 6 and 10mm Teg Tabs, and no Teg Tabs (refer to Seismic Force Calculator)
• End connections must be detailed as shown in this Design Guide. No substitution is permitted without specific engineering design
• Maximum tee spacing must be 1200mm in any direction
• Ceiling must be non-trafficable
• Ceiling must be non-structural (ceiling system does not provide structural stability to the building e.g. acting as a ceiling diaphragm)
• Install and fix all lay-in ceiling panels with correct hold-down clips in full conformance with USG specifications. Where point accessibility is required, nominate un clipped panels with a visual marker ego coloured sticker / board pin etc)
• Ceiling weight must include ceiling tiles, suspension grid, lighting, any other services, and insulation if laid
on the grid
• Individual ceiling tiles must not weigh more than 7.5kg. All items weighing more than 7.5kg must be supported independently from the ceiling (including recessed or surface mounted luminaires, air conditioning cassettes etc) unless covered by specific engineering design (refer to page 6 for further guidance)
• All interior partition walls must be supported independently from the ceiling (including independent horizontal restraint to top of wall), or their weight must be included in the ceiling seismic mass calculations, including specific consideration of the seismic load on each individual ceiling tee (obtain specific advice from a structural engineer)
• All evacuation and life safety systems must be supported independently from the ceiling, and must be likely to
remain functional even if the ceiling collapses
• There must be no other reason why ceiling movement/damage or falling tiles would cause an unusually high level of hazard or damage (e.g. cause release of hazardous substances/organisms, damage to electrical reticulation).
• Ceilings must be installed in accordance with: AS/NZS2785; USG DONN Brand Grid Suspension Systems brochure*;  and this document. *Note: Seismic Design may require heavier grid options than required for vertical loads
• Perimeter fixing rivets must be aluminium. No substitution is permitted

Key Technical and Engineering Assumptions

• AS/NZS2785:2000 has been interpreted in light of the more detailed guidance in NZS1170.5:2004, Section 8 "Requirements for Parts and Components". It is assumed that non-structural, non-trafficable suspended ceilings that satisfy the definition of a Category P.7 part in NZS1170.5, Table 8.1 are only required to satisfy Serviceability Limit State criteria. The generic ceilings specified on pages 7-23 of this brochure have not been designed to satisfy the requirements in AS/NZS?785, Section 3.3.4 during an ultimate limit state seismic event

• Standard design unless otherwise stated is based on a 10mm seismic clearance. If more is required this need to be specifically requested and priced for

• Unless your quotation specifically states that it is designed for an Serviceability Limit State(SLS)  the designs and quotation will be for a  Ultimate Limits State(ULS). 

• Annual probability of exceedance for design earthquake is 1/25 (for serviceability level earthquake)
• The ceiling ductility is assumed to be μ=1.0 (for serviceability level earthquake)

Producer Statements and Warranties

• The cost of your quotation does not cover the cost of obtaining a PS1 (Design), PS2 (Design review) and PS4 (Construction review) producer statements, however these can be obtained based on the quoted design at an extra charge. If a PS1 design is required for the project and this was not available at time of tender then any additional or upgraded components and their associated labour will also be charged as an extra

• We are able to supply you with a PS3 (construction) or warantee documents at no additional charge to the quoted price. These are supplied on request only.