The full article by Jenni Tipler, summarised in part here, first appeared in the BRANZ Build magazine 164 (February 2018), as part of a seismic learnings feature.
Read the article (Build magazine website).
A construction detail is under the microscope and changes have been made to the standard for concrete construction, NZS 3101.1&2:2006, after the poor performance of some mid-level buildings in the magnitude 7.8 Kaikoura earthquake in November 2016.
One of the most significant structural failures occurred at Statistics House in the CentrePort Harbour Quays business park where the building suffered the partial collapse of two floors.
- The Ministry of Business, Innovation and Employment (MBIE) commissioned an independent investigation into the building performance to find any implications for the building regulatory system.
- The expert panel noted vulnerabilities in the design of buildings with precast concrete floor systems in combination with frames that might be affected by beam elongation.
- The panel recommended that NZS 3101.1&2:2006 be reviewed to ensure that matters highlighted by the unacceptable structural performance of Statistics House are addressed within the design standard.
Updating NZS 3101.1&2:2006
NZS 3101.1&2:2006 incorporating Amendment 3 includes:
- a section on beam elongation
- provisions for earthquake actions greater than the ultimate limit state
- significant revisions to precast concrete floor seating requirements.
The revised standard was published in August 2017, and soon after, MBIE began the consultation process to cite the latest revision of the standard in the Verification Method for compliance with Building Code clause B1 Structure.
In the Build magazine article, you’ll find detailed information on the amendments to NZS 3101.1&2:2006 Concrete structures standard including:
- a table of the changes prompted by the Kaikoura earthquake
- a discussion of the proposed ban on the loop bar hanger detail in new construction
- the history of loop bar hangers
- how the Kaikoura earthquake damage prompted the proposed ban.
Image by Lcmortensen (Own work) CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0), via Wikimedia Commons