AS/NZS 5131 explained: structural steelwork fabrication and erection

AS/NZS 5131 sets out what a fabricator and an erector have to do, and have to be able to demonstrate, to build structural steelwork: the quality management, the documentation, the welding control, the tolerances and the inspection. It introduced construction categories to Australian steelwork, and that is the part that changed how fabricators are selected.

What AS/NZS 5131 covers

It is a fabrication and erection standard, so it covers execution rather than design:

• construction categories, and how the category is selected
• the quality management and documentation a fabricator must have
• fabricator and erector capability, including personnel competence
• material traceability and identification
• cutting, forming, holing and assembly
• welding, by reference to AS/NZS 1554 rather than by repeating it
• bolting and mechanical fastening
• protective treatment
• geometric tolerances, both in the shop and on site
• inspection, testing and the records that have to be handed over

Construction categories CC1 to CC4

The central idea of AS/NZS 5131 is that requirements should scale with consequence. Four construction categories do that:

Selection considers the consequence of failure, the type of loading including fatigue and seismic action, and the complexity of the structure and its execution. The category is nominated in the project documentation, and if it is not nominated the standard has a default position, so somebody has chosen even when nobody has decided.

The reason this matters commercially: the higher categories bring the company level welding quality requirements of AS/NZS ISO 3834 into play, along with a nominated welding coordinator whose competence has to match the work. A fabricator without that in place is not able to tender for the work, regardless of how good the welding is.

Demonstrating that capability to a client is what AWI fabricator certification is for. It assesses the shop against the requirements for a nominated construction category and issues a certificate that names it.

Which ISO 3834 level applies to each category

Checked against AS/NZS 5131:2016 incorporating Amendment 1, August 2020. The notation matters here, so it is worth being exact. Clause 7.1.1.1 says welding shall be undertaken in accordance with the relevant part of AS/NZS ISO 3834. The mapping of level to construction category is recommended, not mandated:

One consequence of that mapping catches people out, and the standard says it in a note to the same clause: at CC1, the normative requirements of the relevant part of AS/NZS 1554 exceed those of ISO 3834.4. Holding the elementary level does not put a fabricator ahead of the welding standard it still has to meet. Implementation guidance for the series is AS/NZS ISO 3834.6.

What applies when nobody nominates a category

Clause 4.1.2 settles it, and it is a “shall” rather than guidance: the construction category shall be nominated in the construction specification, and if no construction category is specified, CC2 applies. So a shop that takes on work against a silent specification is working to CC2 whether anyone said so or not, which means AS/NZS ISO 3834.3 as the recommended welding quality level.

Two related points from the same clause. CC4’s requirements are deliberately not fully defined in the standard: it covers unusual or special structures where the additional requirements above CC3 are set project by project. And a single structure can carry more than one category, provided every part is categorised.

Selection is the designer’s call. Appendix C, which is informative rather than normative, derives the category from three inputs: the importance level from the National Construction Code or AS/NZS 1170.0 Section 3, a service category reflecting fatigue and seismic exposure, and a fabrication category reflecting fabrication complexity. Tables C3 for Australia and C4 for New Zealand turn those three into a category.

Personnel competence, by category

Clause 7.4.3 puts welding coordination on every construction category, not just the higher ones: coordination shall be maintained during execution by personnel suitably qualified for and experienced in the operations they supervise. Table 7.4 sets the rest.

ISO 9606-1 is accepted in place of AS/NZS 2980 at CC3 and CC4. At CC2, where a coordinator holds no formal qualification, the standard’s own answer is that competence should be assessed by professional interview, which is a lower bar than a certificate and a higher bar than an assertion. For quenched and tempered steels in groups 8Q to 12Q, coordinators are recommended to hold specific technical knowledge of welding those steels.

The step from CC2 to CC3 is the expensive one. Welder qualification moves off AS/NZS 1554 and onto AS/NZS 2980, coordinator qualification moves to ISO 14731, and identification and traceability of both welders and weld procedures becomes mandatory. None of that is weld quality. It is qualification and record keeping, and it takes months rather than weeks to put in place.

Table 7.4 lists examples of qualifications that satisfy ISO 14731 for CC3 and CC4. At the basic knowledge level they include AS 2214, AS 1796 certificate 10, the New Zealand Institute of Welding Supervisor’s Certificate, and the IIW International Welding Specialist. Specific knowledge is the IIW International Welding Technologist or the NZIW certificate in welding engineering; comprehensive knowledge is the IIW International Welding Engineer.

Who needs to know AS/NZS 5131

• Steel fabricators and erectors, whose ability to win work now depends on demonstrating a category capability.
• Welding supervisors and coordinators, since the category sets the competence expected of them. AS 2214 certification is the usual evidence.
• Structural engineers and specifiers, who have to nominate the category rather than leave it to the shop.
• Builders and principal contractors assessing whether a subcontractor can actually deliver the category they have been given.

Related standards

• AS 4100, steel structures. The design standard AS/NZS 5131 supports. Not yet in this library.
• AS/NZS 1554, structural steel welding. Called up for all welding requirements.
• AS/NZS ISO 3834, quality requirements for fusion welding. Brought in at the higher construction categories.
• AWI fabricator certification, the independent assessment against this standard.
• AS 2214, certification of welding supervisors for structural steel welding.
• AS 1796, certification of welders.

Getting a copy of the standard

AS/NZS 5131 is published by Standards Australia and is not free. If you fabricate structural steel, this and AS/NZS 1554.1 are the two documents most worth owning outright rather than borrowing.

Getting certified to AS/NZS 5131

Reading the standard tells you what is required. A client wanting evidence usually wants a certificate from somebody who does not work for you.

AWI certifies steelwork fabricators to AS/NZS 5131, at the construction category your work is specified at, on its own or combined with AS/NZS ISO 3834.