Update on Grade 500E reinforcing steel
Starting in 2003, when concerns were raised about the performance of Grade 500E reinforcing steel, the Building Industry Authority and then the Department led investigations and informed industry about the characteristics of the material and good practice in its use. Publications issued were Report on Grade 500E Reinforcement (July 2005); Practice Advisory No. 1 Bend the bar but not the rules (July 2005, revised December 2005); Practice Advisory No. 7 Use with care (July 2005); and a chart: Reinforcing Steel in New Zealand - A quick guide for designers, building consent authorities and contractors (June 2005, revised on the Department's website March 2006), and an article on Grade 500E reinforcing steel in the July 2006 edition of Codewords (Issue 13).
Since this material was issued, there have been significant changes in the supply market of Grade 500E reinforcement, making the information on the chart out of date. Research, commissioned by the Department, into the effect of bend diameter and temperature on the ductility of Grade 500E reinforcement was recently completed. This has confirmed the adequacy of bend diameters specified in NZS 3101 (2006), at least for temperatures above minus 10°C and applies to both micro-alloy (MA) and quenched and tempered (QT) types.
To update the situation, the Department:
- has prepared a detailed paper describing the recent research. This is on the Department's website and will be published in the upcoming edition of the Journal of the Structural Engineering Society of New Zealand (SESOC)
- is updating the quick guide chart to reflect changes in the industry and the results of the bend diameter research
- is updating Practice Advisory No. 7 to take account of the research and the industry changes.
It is expected that these documents will be issued by January 2009.
The detailed paper is on our website at: www.dbh.govt.nz/builders-trades-and-designers