Use of Cast Iron Anchors and Couplers - They Are Not Banned
Sunday, 20 January 2019
This article seeks to address recent confusion around the use of cast iron anchors and couplers, and clarify that compliance with the New Zealand Building Code can be demonstrated by an alternative solution respecting the performance based building code system.
The most recent amendment to NZS 3101:2006 Concrete Structures Standard: Amendment 3 issued in August 2017 does not permit the use of cast iron mechanical anchorages and couplers for designs undertaken in accordance with this Standard (Cl. 126.96.36.199). This amendment of NZS 3101 was cited in Amendment 16 of the Acceptable Solutions and Verification Methods for New Zealand Building Code Clause B1 Structure that came into effect on 3 April 2018. This cited version of NZS 3101 provides a means of demonstrating compliance with the structural provisions of the New Zealand Building Code for the design of concrete structures. A modification made to the citation of the Standard permitted the use of cast iron anchors and couplers up until 1 November 2018. This date has now passed resulting in the situation that cast iron anchors and couplers cannot be incorporated in a design solution in accordance with the cited NZS 3101.
A review of other international jurisdictions with similar levels of seismic activity indicates that their Standards do not contain provisions that restrict the material of choice for specifying mechanical anchorages or couplers as long as the performance requirements are met. This respects the principles of a performance based building code system that New Zealand also operates.
The actual ban of using cast iron anchors and couplers is a specific requirement of the New Zealand Transport Agency (NZTA) for the design of their highway bridges that follow the requirements of the New Zealand Transport Agency (NZTA) Bridge Manual.
It is important to remind those involved in the design and construction of concrete structures that it is not mandatory to use the provisions of a Standard such as NZS 3101 to demonstrate compliance with the structural provisions of the New Zealand Building Code, and that compliance with the Code can be demonstrated by other means such as an Alternative Solution respecting the performance based building code system.
It is also important to note that cast iron anchors and couplers have not been banned as a building product or building method under the provisions of the Building Act 2004. (To date only one building method has been banned - the installation of foil insulation in residential buildings in 2016.)
It is therefore suggested that designers who want to incorporate anchors or couplers (of any material) in a design solution undertake specific design to demonstrate compliance with the structural provisions of the New Zealand Building Code. This can be done in a number of ways, including conducting material testing, providing technical data and other expert evidence. Some recommended test methods are provided in the following ISO documents (and these align with test methods recommended in the October 2018 update to the NZTA Bridge Manual - https://www.nzta.govt.nz/resources/bridge-manual/bridge-manual.html):
- ISO 15385-2 Reinforcement Couplers for Mechanical Splices of Bars – Part 2: Test Methods
- ISO 15698-2 Headed Bars – Part 2: Test Methods
When submitting a design to the Building Consent Authority (BCA) in support of a building consent application it is important to provide all the relevant evidence to the BCA so they can be satisfied that the proposed alternative design solution will meet the requirements of the New Zealand Building Code.
More information on Alternative Solutions can be found on the
MBIE website - https://www.building.govt.nz/building-code-compliance/how-the-building-code-works/different-ways-to-comply/alternative-solutions/
The Structural Engineering Society of New Zealand (SESOC) intend to publish a paper that will provide further background on issues related to mechanical anchorages and couplers.