Stainless Rebar Reduces Waste
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THREADED REBAR: Conventional threading (top) and Rotherbar (bottom) |
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Innovative fabrication technique reduces cost, lead time
Nickel magazine, Sep. 00 -- Rotherbar, developed in the U.K., promises to boost demand
for stainless steel reinforcing bar in the construction industry by reducing costs.
Developed by Civil Engineered Products Ltd., of Rotherham, England, the product eliminates two problems
previously associated with threaded stainless steel rebar, namely high initial costs and long lead times.
Conventional threaded rebar has a thread machined into it, and the root of the thread is the smallest cross-sectional area and therefore the highest-stressed portion of the bar. It is here where the bar is most likely to fail. In addition, the unthreaded portion of the bar is not utilized to its full capacity, even though the user has paid for that extra metal.
With Rotherbar, S30400 metal is welded on to a S30400 stainless steel bar, increasing its diameter where the thread is cut. The root diameter of the thread is therefore about the same or greater than the diameter of the remainder of the bar. No metal is wasted and the user pays less for the equivalent performance.
Rock bolts are a good example of how this product can be used. They consist of a bar with ribs anchored by grout at one end and fitted with a nut and washer for tensioning at the other end. In this application, Rotherbar gives a weight saving of about 40% without any loss of strength in comparison with conventional rock bolts. The cost savings which results from the weight reduction and material savings is about 50%.
To date, Rotherbar has been used to retain the walls of a road bridge in Northamptonshire, England, and to strengthen the Priory Bridge in Southend-on-Sea, in the county of Essex.
Ladder rungs have also been manufactured using Rotherbar. In this application, plain ends are needed for welding into the stiles, with a tread pattern required on the centre portion of the bar.
The company is assessing the feasibility of welding non-galling stainless steel threads on to S31600 bar. The ability to add threads of different composition to the parent bar would increase market potential.
The relatively simple equipment required to manufacture Rotherbar renders it portable and ideal for producing components close to the point of use.
The product has been patented, is a registered trademark of Civil Engineered Products and has received recognition from the U.K. Design Council, being designated a millennium product.
Photo: Civil Engineered Products
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Mick Haynes |
