Performance of non-structural systems
Non-structural systems include all of the elements that are not part of a building’s primary structure but are still required for the building to function. This includes mechanical, electrical, plumbing and other engineered systems and services. Building contents, such as furniture, fixtures and fittings, are not non-structural systems.
Many in the industry consider these systems as low risk during a seismic event and should be given secondary consideration behind ensuring other aspects of buildings, particularly the structure, are seismically resilient.
In most cases, non-structural systems present a lower risk to life in a large earthquake than the structure itself (although not always). However, poorly restrained non-structural systems can render a building unusable, leaving building owners and occupants facing major business interruptions and economic impact caused by building downtime.
Surveys following several significant earthquakes around the world indicate that approximately 85 percent of the cost associated with building damage is related to non-structural systems. Following the 2010 Darfield earthquake, damage to one of the most susceptible non-structural systems – suspended ceilings – was estimated to have affected 10–15 percent of all commercial buildings in the region. Another report to the Canterbury Earthquakes Royal Commission estimates that almost every building in Canterbury received non-structural damage of some type during the 2010–11 earthquake sequence. When non-structural components typically make up 60–80 percent of a building’s total value, this damage represents a significant economic impact.