FIGURE 25.27 Slip-critical and bearing-type connections: (a) slip-critical connection; (b) bearing-type connection; and (c) behavior of bolt connections (Nagai 1994).

\ Tension bolts

FIGURE 25.28 Tension-type connection.

There are three types of high-tensile-strength bolted connections: the slip-critical connection, the bearing-type connection (Figure 25.27), and the tensile connection (Figure 25.28). The slip-critical (friction) connection is most commonly used in bridge construction as well as other steel structures because it is simpler than a bearing-type connection and more reliable than a tension connection. The force is transferred by the friction generated between the base plates and the splice plates. The friction resistance is induced by the axial compression force in the bolts.

The bearing-type bolt transfers the force by bearing against the plate as well as making some use of friction. The bearing-type bolt can transfer larger force than the friction bolts but are less forgiving with respect to the clearance space often existing between the bolt and the plate. These require that precise holes be drilled and at exact spacings. The force transfer mechanism for these connections is shown in Figure 25.27. In the beam-to-column connection shown in Figure 25.26, the bolts attached to the column are tension bolts while the bolts on the beam are slip-critical bolts.

The tension bolt transfers force in the direction of bolt axis. Tension type of bolt connection is easy to connect on site but difficulties arise in distributing forces equally to each bolt, resulting in reduced

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