Structural beam bending is often done for the purpose of cambering. (Camber is the amount of deflection provided in the opposite direction of loadings.) An excellent article in Modern Steel Construction, $ave More Money (March 2008), states that “the minimum length of a beam to be cambered is about 25 ft. Why? Because the fabrication jig that is used to camber beams is usually configured with pivot restraints that hold the beam from 18 ft to 20 ft apart. To make sure there is adequate beam extending beyond this point to resist the concentrated force from the cambering operation, a 25-ft beam is generally required.”
This analysis envisions the use of what is commonly called a “cambering machine,” a device where one or two hydraulic cylinders push on various points of a beam which is restrained at its ends. If the beam bending is done on what is commonly called a “3-roll bender” or a “section bender” or an “angle roll,” however, other cost-saving considerations apply:
1. Regarding the minimum length of a beam to be cambered, with our roll-curving processes we have put a 3 inch camber in the following sections: W12 x 26# x 17’ 6”, W12 x 35# x 22’, and W12 x 35# x 16’ 10”
2. We have received some feedback that a uniform curve in a cambered beam is superior to a point-loaded camber. One service center sent us dozens of beams to be cambered to replace point-cambered ones.
3. We have put a 1-1/2 in. camber in some W44 x 290# beams 64 ft. long and a 1-3/4 in. camber in some more W44 x 290# beams 64 ft. long. All these were among the first beams of this size domestically produced.
So, when considering ways to $ave money in cambering, consider contacting a Bender/Roller, i.e. a company that specializes in structural beam bending often using 3-roll bending equipment.