Shank diameter, d

(a) Countersunk head (b) Round head Fig. 10.2. Common types of wood screws.

(c) Coach screws Dowels and bolts

Dowels are cylindrical rods generally made of steel. They have a smooth or striated surface and are available in diameters from 6 mm to under 30 mm. Bolts are threaded dowels with hexagonal or semi-spherical heads and hexagonal nuts and range in sizes up to 30 mm in diameter. Dowels and bolts are commonly used in connections that require a higher lateral load carrying capacity than will be possible from the use of nails or screws. Bolts can also be used in axially loaded tension connections but dowels cannot.

Dowels and bolts can be used in two-member connections but the most common connection type involves three or more members in a multiple shear arrangement. The side members can be either timber or steel. When bolts are used, washers are required under the bolt head and under the nut to distribute the loads, and when tightened, a minimum of one complete thread on the bolt should protrude from the nut. Typical examples of dowels and bolts are illustrated in Figure 10.3.

Fig. 10.3. Typical dowels and bolts.

Table 10.1 Main design requirements for metal dowel type connections under lateral or axial loading and the associated EC5 limit states

Design or displacement effect

EC5 limit states

Lateral and/or axial loading strength

0 0

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