The New Zealand Steel Structures Standard states that high strength structural bolts shall be supplied to AS/NZS 1252. This standard was republished on 23rd December 2016 after undergoing a major revision. The main technical changes incorporated in the new edition relate to updated testing and conformity requirements, the inclusion of the nominated European standard EN 14399-3 property class 8.8 HR bolt as a “Deemed to satisfy” alternative and an additional European EN 14399-3 high tensile property class 10.9 HR.
A significant change to AS/NZS 1252 has been the creation of Part 2, “Verification testing for bolt assemblies”. This represents a restricted form of third-party conformity assessment to provide confidence in products manufactured to AS/NZS 1252.1. Implementation of the AS/NZS 1252.2 verification test requirements has been problematic due a lack of test equipment in Australasia to undertake all the prescribed test procedures, and concern that the test requirements are excessive for routine batch testing of product from regular suppliers. Consequently, the requirements of AS/NZS 1252.2:2016 have not been fully implemented, either in New Zealand or Australia.
The Steel Structures Standard material provisions for seismic applications are intended to ensure that the grade of steel chosen can meet the expected inelastic demand in both seismic and non-seismic applications (SNZ, 1997a). This includes suppressing brittle failure. The current NZS 3404 1997/2001/2007 material requirements are identical for category 1, 2, and 3 members, even though the inelastic seismic demand from category 3 members is much lower than that from category 1 and 2 members. This lack of differentiation of material requirements has created problems sourcing compliant steels for seismic-resisting systems.
The Structural Steelwork – Fabrication and Erection standard AS/NZS 5131 (SA/SNZ, 2016c), is cited as an acceptable standard for demonstrating compliance with the Building Code. This standard published in 2016, was developed in response to the increased compliance risk posed by global sourcing of fabricated structural steelwork. AS/NZS 5131 defines what competent structural steel contractors must do to control and demonstrate the quality of their work.
Threaded bars are commonly used in the structural engineering industry. It is used as replacement for long bolts as well as for concrete anchors and foundation bolts. This product is not covered under New Zealand Standard AS/NZS 1252, ‘High strength steel bolts with associated nuts and washers for structural engineering’. This article is intended to provide information on the appropriate standard to specify for threaded rods used for foundation bolts and the recommended verification testing.
In April 2016, the suite of AS/NZS structural steel product standards were republished (AS/NZS 1163, 3678, 3679.1-2) (SA/NZS, 2016). This paper provides a summary of the key changes, the basis for these changes and interim recommendations until full supply of steel products to the latest standard is available.
The globalisation of the structural steel supply chain has sparked concern over the quality of fabricated steelwork in New Zealand building projects when sourced from low-cost countries. Demonstrating compliance of imported material with the requirements of the New Zealand structural steel and welding standards can be very challenging: there are cultural, geographical and language barriers, and often a lack of independent quality assurance associated with offshore fabricator workshops. Guidance for ensuring compliance of structural steelwork is provided in the following article:
- Fussell, A., Cowie, K., Hicks, S., Karpenko, M., Ensuring Compliance of Structural Steelwork – Regardless of Origin, Steel Advisor QLT1001, Steel Construction New Zealand, 2016 (This article was first published in SESOC Journal Volume 29 No 1 April 2016)
In response to requests from Building Control Authorities a checklist has been developed as a guide to assess compliance of imported fabricated steelwork. The checklist is to be read in conjunction with the above referenced article. The checklist provides normative references to the corresponding sections of the NZS, AS/NZS standards and defines documentation required to claim compliance. Depending on the outcome of the assessment, the fabricated steelwork may be subject to additional NDT and (destructive) testing.
This article was first published in SESOC Journal Volume 29 No 1 April 2016.
The globalisation of the structural steel supply chain has sparked concern over the quality of fabricated steelwork in New Zealand building projects when sourced from low-cost countries. Demonstrating compliance of imported material with the requirements of the New Zealand structural steel and welding standards can be very challenging: there are cultural, geographical and language barriers, and often a lack of independent quality assurance associated with offshore fabricator workshops.
This situation has placed greater onus on Construction Reviewers (typically Professional Engineers), as the technical expert relied upon by Building Control Authorities and clients to ensure steelwork for New Zealand building and infrastructure projects meets the requirements of the New Zealand Building Code.
The aim of this paper is help Construction Reviewers better understand their role and that of the fabrication company in achieving this end. It will also discuss international and local quality initiatives that will make the Construction Reviewer’s role simpler and lower the risk of non-compliance to them. This risk is very real, in Australia there have been examples of Professional Engineers being sued for damages to cover the cost of expensive remedial work associated with non-compliant fabricated products from low cost economies (SCNZ 2014).
Recent reports indicate that some imported steel may show elevated levels of boron; traditionally steel in Australia and New Zealand has been made without boron additions. The welding requirements of AS/NZS 1554 have been established without considering the effect of boron as an alloying element. This article discusses steps that should be undertaken by the fabricator to ensure the integrity of the steel fabrication work when welding structural steel with elevated boron levels.
Australian/ New Zealand Standard AS/NZS 2312 Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings provides guidelines for selection and specification of coating systems for corrosion protection of structural steelwork. The designer can choose from a selection of systems based on exposed service life to first maintenance for various environments. AS/NZS 2312 has recently undergone a major update. A short summary of the major changes to AS/NZS 2312 and use of the standard is provided in Steel Advisor GTG1008. In addition changes have been made to the designation system for Inorganic Zinc Silicates which will be highlighted in this article.
In New Zealand we have the undesirable situation of an aged Structural Steel standard by international standards and we also have two sets of standards provisions that address the minimum requirements for the fabrication and erection of structural steelwork (NZS 3404:1997 – including amendments 1&2 and NZS 3404.1:2009) This is compounded by the fact that that the most recent provisions are not cited as a verification method document.
The introduction of a new joint Australia/ New Zealand structural steelwork fabrication and erection standard on the face of it appears to be adding to the problem. In this paper the rationale for developing this new standard is discussed along with an outline of its content and a vision of how this standard might fit within a suite of AS/NZS standards covering the design, fabrication and erection of composite and non- composite structures in New Zealand
Australian/ New Zealand Standard AS/NZS 2312 Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings provides guidelines for selection and specification of coating systems for corrosion protection of structural steelwork. The designer can choose from a selection of systems based on exposed service life to first maintenance for various environments. AS/NZS 2312 has recently undergone a major update. Galvanizing and metal spraying have now become separate standards. A short summary of the major changes to AS/NZS 2312 and use of the standard is provided.
Structures designed to the Steel Structures Standard, NZS 3404, are required to be able to resist collapse under a maximum considered earthquake as directed by the Loadings Standard, NZS 1170.5. Brittle systems are not permitted. The nature of steel material is that it always contains some imperfections, albeit of very small size. When subject to tensile stress these imperfections (similar to very small cracks) tend to open. If the steel is insufficiently tough, the 'crack' propagates rapidly, without plastic deformation, and failure may result. This is called 'brittle fracture', and is of particular concern because of the sudden nature of failure. The toughness of the steel, and its ability to resist this behaviour, decreases as the temperature decreases. In addition, the toughness required, at any given temperature, increases with the thickness of the material. A convenient measure of toughness is the Charpy V-notch impact test. This test measures the impact energy (in Joules) required to break a small, notched specimen by a single impact blow from a pendulum. The tests are carried out with the specimens at specified (low) temperatures, and the steel material standards specify the required minimum impact energy values for different grades.
In multistory construction columns splices are provided for convenience of fabrication, transport and erection. If required the splices are located just above the floor level, which enables easy access to the joint.
There are two types of splice connection, full contact bearing and non-bearing. As the name suggests in bearing splices the axial load is transferred directly to the column below by full bearing contact, bolts and plates are intended to hold columns in place. In non-bearing splices the load is transferred through bolts and splice plates.
The design of bolted column splices with minor axis bending moment, ie two way moment resisting frames, is a complex process. There is not much literature available on this topic. A design guide that briefly discusses this topic is the South African Institute of Steel Construction’s Structural Steel Connections Guide or the “Green Book”. Another source of guidance is the Steel Construction Institute Publication 207, which covers the non-bearing splices with minor axis bending.
This article will cover design of bearing and non-bearing splice connections with minor axis bending based on the procedures outlined in the aforementioned guides, and relate the design equations to NZS 3404.
The Steel Structures Standard, NZS 3404, references the AS/NZS 1554 suite of standards for compliance of welding consumables. NZS 3404 includes additional requirements limiting the heat input in the deposited weld metal for welds subject to earthquake loads or effects. This article discusses the background to these requirements, identifies welding processes restricted by the heat input limits and how to qualify welding process that are restricted by the heat input limits.
Ductile eccentrically braced frames designed in accordance with the New Zealand Steel Structures Standard, NZS 3404, provide life safety during a design level or greater earthquake; however, the eccentrically braced frame active link may sustain significant damage through repeated inelastic deformation. This may necessitate post-earthquake replacement of the active link. A bolted replaceable active link can be used to facilitate replacement after a strong earthquake, which reduces repair costs. New Zealand design guidance for the seismic design of steel eccentrically braced frames was first published in 1995 by the New Zealand Heavy Engineering Research Association within HERA Report R4-76 and has been widely used in practice. This guidance has been recently updated and now includes seismic design procedures for eccentrically braced frames with replaceable links. This article covers the development and research of eccentrically braced frames with replaceable links. This includes discussions of the comprehensive research programme recently completed in Canada investigating the performance of eccentrically braced frames with replaceable links and finite element analysis undertaken by the New Zealand Heavy Engineering Research Association, to verify the design procedure for eccentrically braced frames with replaceable links.