How to Bend Rebar: Does Bending Bars in the Field Weaken Them?

The most common questions involving working with reinforcing bar have to do with how to bend rebar in a way that doesn't affect the steel's structural properties or overall strength.

In particular, the bending and re-bending of rebar in the field has emerged as one of the most controversial procedures related to reinforced concrete construction projects.

How to Bend Rebar

The reasons for bending or re-bending rebar on-site are many and varied. Unforeseen circumstances, such as having rebar accidentally run over by a vehicle, are impossible to avoid. Likewise, last minute corrections and adjustments to building specifications are also a common occurrence in the fast-paced environment of modern building construction.

For those concerned about the effects of bending on the structural properties of rebar, a 1992 study outlined in Concrete International yielded some interesting results that can serve as a guide for how to bend rebar.

For example, in cold conditions, bar sizes #10 and #13 showed no reduction in either yield or tensile strength and a 20% reduction in elongation. In hot conditions, all bar sizes showed a 10% reduction in both yield and tensile strength and a 20% reduction in elongation.

The best course of action for dealing with uncertainties surrounding the bending of rebar is to always involve an architect or engineer in decision-making. Also, builders would do well to follow the guidelines outlined in the ACI 318-02 Building Code, specifically in Section 7.3.2. Lastly, consult with a qualified rebar supplier like White Cap regarding the optimal conditions for bending rebar.

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