Along with columns and trusses, beams are critical structural members, and they are found in virtually every building. Beams carry transverse loads such as roofs, floors and interior walls, and also plumbing fixtures, refrigerators, desks, and people; they have important load carrying jobs. Their ability to perform can be impaired by careless placing, reckless fastening, and foolish carving or cutting. This can lead to squeaky or un-even floors, sagging and leaking roofs, cracked walls, increased seismic or storm risk, and other problems. Laborers can help guard against these problems by understanding how beams work.
Beams have special names because they are for special jobs or are made in special ways. See the appendix for a list.
Beam parts:
Beam parts are best identified by reference to the end of an I-beam. There are three special areas, namely the two Flanges, and the area in between them, called the Web. Each of these parts has a separate job in load carrying. A horizontal beam properly placed to carry a vertical load has one flange on top and one on the bottom. The line along the beam halfway between the top and bottom flanges is the beam centerline, called the “Neutral Axis”.
Beams are supported by direct bearing on something else, e.g. a bearing wall, pier, truss, column, or shear through hardware connections. The number and place of supports are very important in determining a beam’s load carrying capacity. A beam supported only on its two ends is called “Simply Supported”. If there are more than two supports under a beam, it is called “Continuously Supported”. A beam overhanging a support and carrying a load on the overhang is “Cantilevered”. The distance between supports is the “Span”.
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