General:

I beams have a variety of important uses in the structural steel construction industry. They are often used as critical support trusses, or the main framework, in buildings. They ensure a structure’s integrity with relentless strength and support. If you have a beam of steel which has a basic permissible bending stress of about 23000 lbs per square inch, by the time you make allowances for the span and the lack of restraint, the actual bending stress that the beam can handle is down to about 6100 lbs per square inch under these conditions. When supporting joists that span 12 feet with no overhang beyond the beam, a double ply beam can span in feet a value equal to its depth in inches. A double 2×12 beam can span 12 feet; a (2) 2×10 can span 10 feet and so on. They are commonly made of structural but may also be formed from aluminium or other materials. A common type of beam is the rolled steel joist (RSJ)—sometimes incorrectly rendered as reinforced  joist. British and European standards also specify Universal Beams (UBs) and Universal Columns (UCs).