Figure 1-26.—Scabs.Figure 1-27.—Split ring and split-ring joints.washers under both the bolt head and the nut. The boltsare then tightened until the washers bite well into thewood to compensate for future shrinkage. Bolts shouldbe spaced a minimum of 9 inches on center and shouldbe no closer than 2 1/2 inches to the edge or 7 inches tothe end of the timber.Driftbolts, also called driftpins, are used primarilyto prevent timbers from moving laterally in relation toeach other, rather than to resist pulling apart. They areused more in dock and trestle work than in trusses andbuilding frames. A driftbolt is a long, threadless rod thatis driven through a hole bored through the member andinto the abutting member. The hole is bored slightlyFigure 1-28.—Shear plate and shear-plate joints.smaller than the bolt diameter and about 3 inches shorterthan the bolt length. Driftbolts are from 1/2 to 1 inch indiameter and 18 to 26 inches long.Butt joints are customarily connected usingdriftbolts; however, another method of makingbutt-joint connections is to use a scab. A scab is a shortlength of timber that is spiked or bolted to the adjoiningmembers, as shown in figure 1-26.TIMBER CONNECTORSA timber connector is any device used to increasethe strength and rigidity of bolted lap joints betweenheavy timbers. For example, the split ring(fig. 1-27)isembedded in a circular groove. These grooves are cutwith a special bit in the faces of the timbers that are tobe joined. Split rings come in diameters of 2 1/2 and 4inches. The 2 1/2-inch ring requires a 1/2-inch bolt, andthe 4-inch ring uses a 3/4-inch bolt.Shear plates are shown in figure 1-28. Theseconnectors are intended for wood-to-steel connections,as shown in view B. But when used in pairs, they may1-15
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