Steel beams include girders, lintels, etc. The simplest form of steel beam would be a single RSJ or an angle section for carrying small loads. In case of large loads, compounds ( built-up) sections are used.
Compound beams comprise of two or more single RSJs connected together through bolts and separated suitably with separators which hold them in required position. Separators are placed 
to 2 m apart (Fig. 24.9).
Figure 24.9 Compound beam
For still heavier loads, girders are formed by two channels placed back to back and their flange area increased by the addition of one or more plates at top and bottom (Fig. 24.10).
Figure 24.10 Girder
When very large loads are to be handled plate girders are used. A plate girder is one which is a built-up section consisting of top and bottom flanges made up of angles and plates. The web consists of one or more steel plates. The beam is formed by placing the individual pieces in positions and riveting or welding is done to keep then together (Fig. 24.11). As the plate girders are of considerable depth they have to be stiffened laterally to prevent buckling. Angles or T-sections are used as stiffeners and are riveted to the plate girder at suitable spacing (Fig. 24.12).
Figure 24.11 Part elevation of plate girder
Figure 24.12 Stiffeners
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