What is resilience?

This Issue This is a part of the Resilient buildings feature

By and - , Build 141

Resilience was the 2013 buzzword, and 2014 will see a continued focus on how to make individuals, communities, buildings and infrastructure more resilient. But what does resilience mean?

RESILIENCE is a broad concept with many definitions but most include elements of the following, saying that resilience is the ability to:
  • absorb shock in a time of crisis
  • recover the functionality of the building after a disaster or a sudden shock
  • operate appropriately even if parts of the building fail.

Another clear way of looking at resilience, as defined by the US National Infrastructure Advisory Council (NIAC), is ‘the ability to reduce the magnitude and/or duration of disruptive events’.

Four pillars of resilience

Eight principal features are used to define building and infrastructure resilience – some are complementary, others overlap. Thomas O’Rouke defined the four pillars of resilience as robustness, redundancy, resourcefulness and rapidity.

Robustness

Robustness is a key feature of resilience and refers to a building’s potential to cope with stress without failing or losing significant function. For infrastructure, this could be a network’s ability to continue operating after being subjected to external pressures or disturbances.

Redundancy

Redundancy allows for alternative choices, decisions and substitutions in a building system so that there are different recovery options in the case of disaster or when under pressure.

Resourcefulness

Resourcefulness is the ability to manage the impacts of the crisis on the system or building, including mobilising effective people, processes and needed materials after a crisis, so rapid recovery can happen. Frederic Petit believes that, by incorporating resourcefulness into resilience, a system, building or structure can recovery quicker.

Rapidity

Rapidity looks at how quickly the function of a network, or the use of a building, can be restored after a shock. Rapidity is important for resilience of buildings so an analysis of how multi-hazards affect a building, structure or system is recommended.

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Related features

The other four features of resilience that are commonly referred to – capacity, flexibility, tolerance and cohesiveness – overlap with the previous definitions.

Capacity is similar to robustness in that it is seen as the ability of a building or network to withstand disruption. However, capacity also incorporates redundancy to allow infrastructure to absorb additional demand in a crisis.

Flexibility is the ability to be adaptable or change in response to external pressures, although this may be more applicable to networks than buildings.

Tolerance is related to how well a building behaves near its design boundary – whether the system slowly fails as stress increases so there is time for life safety or collapses quickly when stress exceeds the building’s ability to cope. Tolerance is important in avoiding sudden collapse.

Cohesiveness refers to how well different parts of a building work together as a system. In order to incorporate cohesiveness into a resilience measure, building elements and their behaviour should be considered as part of a whole building system.

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