Have you ever stopped and wondered just how some of the fantastically shaped glass and steel buildings are created and what process is used to created the shaped steel framework? Most of the beams that are used to create the graceful curves you see in these buildings started out as perfectly straight "I" beams when they were first cast or forged. It takes a very special piece of equipment known as a steel bender to bend these massive beams to the right shape needed for these structures.
One of the reasons a steel bender is used instead of casting the beam in the shape needed is cost. Steel mills produce thousands if not millions of feet of "I" beams and steel channel every year. This is what the equipment they have is designed to produce and each piece is cast in the same reusable mold or forged using exactly the same process over and over again. It would not be economically feasible to have to create a new mold for just one project or one particular beam.
By sending these straight beams to a plant that has a heavy duty steel bender the architect can have the beams bent into any shape they need to create the framework for the building they have designed. Many of the sports stadiums are perfect examples of this as curved roofs require massive curved "I" beams to support them and the extra added weight of any snow that accumulates on them during the winter months.
The most common form of steel bender uses rollers to bend the steel. Adjustable dies are matched to the size and shape of the beam, while the beam is fed into the rollers which are turning in opposite directions while pressure is applied to the beam. This pressure causes the beam to bend to the exact curve needed for the project in question. While this may not be the most elegant form of bending steel, it is the most economical and frequently used.
One other common type of steel bender is the mandrel press, which is used on the bigger and much heavier beams, bars and pipes that do not need to be bent to overtly tight radii. Here the beam is fed through a press that applies pressure every few inches and slowly creates the sought after curves. While less common than the rolling bender, it is used to create the large load bearing, curved beams that you might see in sports stadiums or huge skyscrapers.