Bend the bar ...but not the rules
With the issue of 5000 Department of Building and Housing bendometers across the industry, there is no excuse for incorrect bending of main reinforcing steel.
For some time, the Department has been reminding concrete construction personnel that incorrect bending of reinforcing steel can lead to poor performance of structures and even failure. The matter was highlighted when the new 500E reinforcing steel became available in New Zealand.
The issue is that reinforcing steel is sometimes being bent to tighter diameters than specified in the New Zealand Standards cited in the Department’s B1 Compliance Document, and therefore does not comply with the Building Code. Bends tighter than specified, especially in 500E steel, can lead to cracking of the main bars and therefore reduction in strength of the concrete member and noncompliance with the Building Code.
The Department devised and produced a ‘bendometer’ for checking whether the bend in a bar is in accordance with the relevant New Zealand Standard. The device incorporates four disks, each with a specific diameter, giving the minimum (inside) bend for that particular bar (10, 12, 16 and 20 mm, see photo). Each disk also has a cutout to quickly check the diameter of the bar being inspected. The correct minimum bend diameter for each size of bar is the same as the corresponding disk diameter.
Other useful information for the user (eg, markings) is given on the back of the disks. While the disks were designed to be used with the main bars and not with stirrups or ties, they can be used with either grade 300 or 500 reinforcement. The disks are attached to a split ring (supplied) for ease of use at the bending or construction site. A one-page instruction sheet is also included.
Some bending devices used by construction personnel bend bars to inside diameters much less than the minimum requirements. The bendometer provides site personnel and building officials with an easy way to check that the requirements have been met. Feedback from the construction industry on the bendometers has so far been very good and there have been a number of letters of appreciation and requests for
Attendees at the recent BOINZ conference received a sample and they proved popular. With the support of Cement and Concrete Association of New Zealand, the bendometer is being promoted to provide a practical measuring device and to raise awareness of the need to bend reinforcement correctly. If you were not on our mailing list, or you or your colleagues would like to receive more bendometers, please let us know by calling 0800 242 243 or by emailing firstname.lastname@example.org