Figure 2-66.-Truss members fastened together with split-ring connectors.A great majority of the trusses used are fabricatedwith plywood gussets (fig. 2-64, views A through E),nailed, glued, or bolted in place. Metal gusset plates (fig.2-65) are also used. These are flat pieces usuallymanufactured from 20-gauge zinc-coated or galvanizedsteel. The holes for the nails are prepunched. Others areassembled with split-ring connectors (fig. 2-66) thatprevent any movement of the members. Some trussesare designed with a 2- by 4-inch soffit return at the endof each upper chord to provide nailing for the soffit ofa wide box cornice.Tension and CompressionEach part of a truss is in a state of either tension orcompression (see fig. 2-67). The parts in a state oftension are subjected to a pulling-apart force. Thoseunder compression are subjected to a pushing-togetherforce. The balance of tension and compression gives thetruss its ability to carry heavy loads and cover widespans.In view A of figure 2-67, the ends of the two topchords (A-B and A-C) are being pushed together(compressed). The bottom chord prevents the lowerends (B and C) of the top chords from pushing out;therefore, the bottom chord is in a pulling-apart state(tension). Because the lower ends of the top chordscannot pull apart, the peak of the truss (A) cannot dropdown.In view B, the long webs are secured to the peak ofthe truss (A) and also fastened to the bottom chord atpoints D and E. This gives the bottom chord supportalong the outside wall span. The weight of the bottomchord has a pulling-apart effect (tension) on the longwebs.In view C, the short webs run from the intermediatepoints F and G of the top chord to points D and E of thebottom chord. Their purpose is to provide support to thetop chord. This exerts a downward, pushing-togetherforce (compression) on the short web.Figure 2-67.—Tension and compression in a truss.2-41
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