BIA Acts On Concerns Over Handling Of Grade 500e Steel

The Building Industry Authority (BIA) is investigating concerns that have recently been raised regarding handling procedures for Grade 500E reinforcing steel, a high strength ductile steel.

The concerns relate to instances of reinforcing bars becoming unacceptably brittle following bending, re-bending or welding. This is a timely reminder that Grade 500E steel requires careful handling in practice, in accordance with the relevant Standards and manufacturer’s instructions.

Given the widespread use of Grade 500E steel, the BIA is keen that the need for proper care in bending and welding is emphasised. The BIA is also examining the known instances of embrittlement to determine if the currently specified restrictions on bending and welding are sufficient.

The BIA’s initial investigations suggest that some bending and welding practices may not be appropriate and that further investigations are required. To this end the BIA is: in contact with New Zealand manufacturers of Grade 500E steel, fabricators and construction companies; seeking factual information from designers, fabricators and builders on instances of problems with Grade 500E steel; liaising with researchers who are studying this issue; liaising with the relevant Standards committees and design and engineering organisations.

The BIA will also be contacting territorial authorities, who are responsible for ensuring that on-site building practices comply with the Building Code, to ensure they are aware of the issue and monitor it more closely.

Although in widespread use, 500E is a relatively new grade of steel and requires more careful on-site handling than other grades. The bending, re-bending and welding of steel has always been an area requiring careful attention, especially with high-strength steel such as Grade 500E.

Until the results of its investigations are available the BIA recommends the following interim measures:

Bending: Take special care to achieve the minimum bend radii given in NZS 3101:1995 ‘Concrete Structures Standard’. Reject any steel that does not comply.

Re-bending: Do not allow re-bending of Grade 500E steel. Reject and replace any steel that has been subject to bending and re-bending.

Welding: Site welding, including tack welding, should not be carried out. Welding can be acceptable but only when very stringent conditions are met, and this requires shop conditions which the BIA doubts can be achieved on-site.

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