Downtown carpark building earthquake risk assessment Downtown carpark building earthquake risk assessment
As part of Auckland Transport’s maintenance and inspection programme a seismic assessment on the Downtown carpark building has been completed. The seismic assessment has rated the building as “earthquake prone”. Structural engineers have confirmed there is no immediate risk to people or property and the carpark will remain open.
The Downtown carpark is one of many buildings in Auckland with this rating. There are 1365 buildings, both public and private, registered as earthquake prone in Auckland.
Auckland is considered a low seismic risk zone, and 35 years is allowed for completion of remedial strengthening work. However, AT is undertaking design work to see if some remediation can begin as early as 2021.
The carpark will stay open and leaseholder agreements will not change. There is no work planned which will affect any leaseholder spaces. The Downtown carpark building is owned by Auckland Council, but managed by AT.
Read the seismic assessment report (PDF 365KB).
Overview
- Auckland is considered a low seismic risk area for moderate earthquakes. It is expected that an earthquake in Auckland would be far less intense than those occurring in other areas with higher seismic activity, such as Wellington.
- Auckland building owners, including council, have 15 years to identify whether a building is earthquake-prone. (Auckland Council owns the Downtown carpark building).
- A building is deemed earthquake-prone if its seismic strength is assessed as being less than 34% of the design standard for new buildings. It would pose a risk to people or other property in a moderate earthquake.
- If a building is identified as being earthquake-prone it is not necessarily unsafe for occupation.
- Auckland Council has 35 years from the time a building is identified by building control as earthquake-prone to complete required strengthening works on its buildings to meet the minimum requirement of 34% of the design standard of a new building.
- Auckland Council's asset risk assessment programme team is completing assessments of all buildings that are likely to be considered earthquake-prone. Updates will be provided to Local Boards, business owners and staff of any health and safety issues and/or likely works required as the programme progresses.
The process for identifying earthquake prone buildings
In 2016, the Building Act 2004 (the Act) was amended to create a nationally consistent approach to the assessment and management of earthquake-prone buildings. The development of the Act used knowledge learned from past earthquakes in New Zealand and overseas. The Amendment Act took effect on 1 July 2017.
The Act requires that Territorial Authorities (local Councils) determine if a building or part of a building is earthquake prone using a specific Earthquake-prone Building (Earthquake-prone Building) methodology. The Earthquake-prone Building methodology sets out how Territorial Authorities identify potentially earthquake-prone buildings, how engineers undertake engineering assessments, and how Territorial Authorities determine whether a building or part is earthquake prone, and if it is, its earthquake rating.
If a building is identified as potentially earthquake-prone, the Territorial Authority must notify the building owner and request an engineering assessment in accordance with the Act.
The Auckland Council website has information about how the Act affects building owners (including council) across the Auckland region, the responsibilities of building owners and the responsibilities of council in identifying potentially earthquake-prone buildings, and the timeframes for doing so. Earthquake-prone buildings are no longer included in council’s earthquake-prone, dangerous and insanitary buildings policy (2011-2016). Additional information can be found on the Ministry of Business, Innovation and Employment website.
Additional information
If a building is confirmed as earthquake-prone this means that the building, or a part of that building, would likely be structurally damaged by a moderate earthquake. It does not mean that the building is dangerous or unsafe to be in at any other time.
A building is deemed earthquake-prone if its seismic strength is assessed as being less than 34% of the design standard for a present-day new building in the same location. It would pose a risk to people or other property in a moderate earthquake.
A moderate earthquake is a concept used by engineers to measure the performance of an existing building against a level of shaking. While a moderate earthquake does not have a specific magnitude, a moderate earthquake can be described as one-third as strong as a theoretical earthquake used in the design of new buildings.
The amended Building Act divides New Zealand into zones of high, medium, and low seismic risk. Auckland is identified as having a low risk of a moderate earthquake.
The Amendment Act identifies some buildings as being potentially more earthquake-prone, these include:
- Unreinforced masonry buildings.
- Buildings constructed before 1976 that are higher than 3 stories.
The seismic assessment report indicates that the seismic rating of the Downtown Carpark Building is 20% of new building standard and has been classified as an earthquake prone building.
In accordance with the Building Act, the Building is classified as an Earthquake Prone Building (“EPB”). Auckland is considered a low seismic risk zone, and therefore a 35-year time period is allowed for completion of remedial seismic strengthening works.
Auckland is considered a low seismic risk zone, and therefore a 35-year time period is allowed for completion of remedial seismic strengthening works.
Because Auckland has a low earthquake risk, the Amendment Act states that Auckland building owners, including council, have a maximum of 15 years to identify whether a building is earthquake prone.
If a council-owned building has been identified as earthquake-prone and a substantial alteration or change of use is planned, council will be required to strengthen the building at the same time.
When a building is confirmed as being earthquake-prone, the local council will request that the building owner attaches a notice on the building. The notice provides information about percentage of the new building standard, the timeframes for repairing the building and options to apply for an exemption. The notice should be placed in a prominent place easily viewed by visitors to the building.
The details of the earthquake-prone building will be added to a national register of earthquake-prone buildings and council will display an earthquake-prone notice in a prominent place in the building.
Council has 35 years from the time a building is identified as earthquake-prone to complete strengthening work. This is the work required to make that building 34% or more of the seismic performance required for a new building in the same location. When works is completed, this will mean the building is no longer classified as an earthquake-prone building.
If a building is a Category 1 listed building with Heritage New Zealand, or is on the National Historic Landmarks list, council can apply for a 10-year extension to complete strengthening works.
There are generally no new risks of imminent danger following an evaluation that shows a building is earthquake prone. An earthquake-prone building is not necessarily unsafe or dangerous to occupy.
Substantial alterations to an earthquake-building are works that:
- Require a building consent, and
- Have an estimate value of at least 25 per cent of the building’s value and more than $150,000.
The Earthquake-prone Building Methodology recommends two engineering assessment types:
- Initial Seismic Assessment (often abbreviated to ISA); and,
- Detailed Seismic Assessment (often abbreviated to DSA). A DSA is a more comprehensive assessment of the strength and capability of a building.
The Amendment Act regulations apply to commercial and residential buildings and some structures are not subject to the regulations, for example, bridges, tunnels, wharves, statues and other monuments that cannot be entered.
Resources
Resources about earthquake-prone buildings is available at:
- Ministry of Business, Innovation and Employment website.
- Auckland Council website.
- NZ government building performance website
- Heritage NZ website.