Insights

Clause A3 of the New Zealand Building Code defines the importance of a structure by its Importance Level (IL), based on the consequences if that structure fails. Five levels are defined, and the required seismic performance increases with each:

• Level 1 (IL1): Low-hazard structures, such as walkways, outbuildings, fences, and walls.
• Level 2 (IL2): Normal structures not covered elsewhere, such as timber-framed houses, car parking buildings, or offices.
• Level 3 (IL3): Structures that may hold crowds or high-value contents, or pose risk to large numbers of people nearby, such as conference centres, stadiums, and airport terminals.
• Level 4 (IL4): Buildings that must remain operational immediately after an earthquake or other disaster, such as hospital operating theatres, triage centres, emergency shelters, and other critical post-disaster infrastructure.
• Level 5 (IL5): Structures whose failure would pose a catastrophic risk to a large area or population, such as dams, nuclear facilities, or biological containment centres.

In Australia, the equivalent seismic loading requirements are set out in AS1170.4, the Australian earthquake loading standard.

Challenge: A hospital in the Canterbury region needed a backup fuel storage tank capable of remaining fully operational immediately after a major seismic event, to keep its standby generators supplied through any outage that followed.

Solution: Fuelchief supplied SuperVault 22,000L tanks, engineered to meet IL4 seismic requirements. To confirm the tank would perform as required, Fuelchief engaged BVT to carry out independent seismic testing, including finite element analysis and a shake test simulating major earthquake conditions.

Result: The SuperVault 22,000L was confirmed able to withstand a major seismic event and continue servicing the hospital's backup power supply immediately afterward, exactly the outcome IL4 compliance is meant to guarantee.

View the Case Study here: Christchurch Hospital