The bending of beams is usually done the “hard way,” i.e. against the strong (x-x) axis or the “easy way,” i.e. against the weak (y-y) axis. Beams can also be curved to multiple radii, off axis, and in two planes including helically.
It is possible to have some distortion in beam bending especially when they are being “pushed to the limits.” For example, when bending beams the “hard way” on a three-roll section bender (also called a “pyramid roll” or “angle roll”), it is common to have a fourth roll pulling on the outside flange to keep the web in tension so that it does not buckle. Pulling on the outside flange, however, can create a dip in that flange which may or may not be acceptable. The final arbiter of what is acceptable, of course, is the customer who is often guided by his engineer. Any web buckling is usually a greater concern.
Distortion is generally less likely to occur when bending beams the easy way. In extreme cases, there may be some “mushrooming” or swelling of the tips of the flanges as that is where the pressure is applied.
With the right machinery, method, material and operator, however, steel beams, like the other steel sections, can be curved successfully to surprisingly tight radii with no distortion.
