Design criteria for engineering systems

NZS 4219:2009 requires engineering systems within a building to be arranged and laid out in a way that accommodates earthquake actions. It states that the location, design, construction and installation of engineering systems should reduce life and injury hazards and protect property and systems from damage or loss of function.

To achieve this, the standard requires engineering systems to be designed, constructed and installed so that the following criteria are met:

  • Components representing a hazard (classification P1, P2, P3) will not collapse, rupture or lose support during an ultimate limit state (ULS) earthquake.
  • Components required for emergency evacuation (classification P4) will not collapse, rupture or lose support during an ULS earthquake.
  • Components required for operational continuity (classification P5) within buildings of importance level 4 are restrained in a manner so that the system is able to continue to perform its functions after a serviceability limit state 2 (SLS2) earthquake.
  • All components are restrained in a manner so that the system retains its structural and operational integrity without requiring repairs after a serviceability limit state 1 (SLS1) earthquake.

The definitions of ULS and SLS earthquake events are given in AS/NZS 1170.0:2002 Structural design actions – Part 0: General principles. Component classifications are defined below.

This video presents a Californian seismic study designed to test the performance of non-structural components in hospitals during an earthquake. The study also considers structural, non-structural and fire protection systems.

When following the NZS 4219:2009 non-specific design pathway to meet these criteria, the design procedure consists of three steps, which the designer should follow for each component:

  1. Determine the earthquake demand on the component.
  2. Determine the forces on the restraint system.
  3. Design the restraint system.

The design criteria are met when the capacities of the restraint exceeds the earthquake demand on each component.