Seismic Solutions

Introduction

Changes in the Seismic Code Requirements for Ceilings - what you need to know
In the past, seismic force levels tended to be considered in certain earthquake-prone locations. But major revisions to the Seismic Standard have changed the requirements, which means that every construction project must include and meet a seismic design category, even those locations that may have had minimal seismic installations in the past.

A changing seismic landscape

Seismic construction standards have been established to control panic during an earthquake and provide life safety to building occupants during and after an earthquake. Major revisions and an inclusion within the joint Standard AS/NZS1170 suite have changed the requirements, with more factors being taken into consideration than seismic installations in the past. These can include, but are not limited to:

  • Soil condition
  • Building construction materials
  • Building usage
  • Building importance
  • Geographic location in NZ
  • Location to fault lines (known)
  • Weight of the ceiling
  • Height of the ceiling from ground level
  • Size of the ceiling

By analysing these criteria for a construction project, you can determine the seismic design requirements for the suspended ceiling(s). This is typically done by the project's structural engineer, but may be involve qualified engineers more familiar with suspended ceilings. To assist the designer and contractor, USG BORAL provides a comprehensive Generic Seismic Design technical brochure that will provide solutions for many common building types.  For projects that fall outside the scope of this document, a Seismic Guidelines brochure details the type of information required for a charted structural engineer with experience in suspended ceilings to calculate specific project design(s).

The three main Standards involving suspended ceilings are:

  • NZS 1170.5 - Structural Design Actions – Earthquake Loads
  • NZS 4219 - Specification for Seismic Resistance of Engineered Systems in Buildings*
  • AS/NZS 2785 – Suspended Ceilings, Design and Installation

* A number of site inspections as a result of the Canterbury earthquakes revealed that the collapse of suspended ceilings often resulted from heavy plenum services/equipment not installed correctly or adequately braced, in compliance with NZS 4219, mandatory under the NZBC. Stricter levels of inspection should be enforced to ensure this type of failure is minimised for new or re-instatement projects.

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