Often overlooked, this is a critical point in the process of manufacturing Anchor Bolts.
We’ve seen many examples of bolts bent on the wrong equipment. Press brakes or some other system that creates one or both of the follow problems;
Problem # 1 The bend is focused on a small spot on the inside radius.
When bent on a press brake, the tool often leaves a dent at the spot where the downward force was applied. Once installed, any upward pressure would create stress, all of which would focus on that dent. (figure 1)
Bent around the proper size mandrel, at the proper speed, the result would be an even radius. Under the same upward pressure the stress is distributed over the full inside radius of the bend. (figure 2)
Problem # 2 The bend radius is too tight and the steel on the outside is stretched too thin.
The inside radius of a bent anchor bolt should never be less than the diameter of the round bar prior to bending. Bending on too tight a radius causes the outer diameter to stretch too thin and reduces the diameter too much. Specification ASTM 1554-07a reads, “The bend section of bent anchor bolts shall have a cross-sectional area not less than 90% of the straight portions.”