Recommended practice for seismic restraint design of suspended ceilings

Abstract

Seismic restraint of suspended ceilings in the New Zealand environment has seen significant evolution over the past decade. Amendments to NZS1170.5 and updates to AS/NZS2785 are intended to drive better earthquake resilience for suspended ceilings, however neither the amendment nor the suspended ceiling standard have been cited by the New Zealand Building Code. Varying interpretation of these standards can lead to inconsistent design and performance of suspended ceilings. There is a different global system behaviour between grid and tile versus plasterboard lined suspended ceilings when they are subjected to horizontal and vertical accelerations. Part of the reason for inconsistency in design stems from minimal shake table testing data available to support design practice for grid and tile ceilings installed in New Zealand. This paper discusses the global system behaviour of both fully floating grid and tile and plasterboard lined suspended ceilings and provides guidance on load paths and design of individual members and connections. Most suspended ceilings are built using manufacturer specific proprietary components which are assembled into an overall suspended ceiling system. To ensure designers can be satisfied these proprietary components have adequate strength and stiffness we have provided a suggested language for specifications to provide more consistency through the industry and ensure supplier test data verifies member and connection capacities.