Joints in Timber Structures

A bolted joint connects two or more timber members by bolts passing through holes bored in the members, with a washer under the head and nut; the bolts transfer the load by bearing on the timber and by their bending.

• Types: lap joints and splices with timber or steel side plates, and tension or compression splices; the bolts are in single or double shear.
• Load per bolt depends on the bolt diameter, the thickness of the members, the species and the angle of the load to the grain (higher parallel to grain than perpendicular to grain).
• Spacing rules (typical): holes $1$ to $1.5$ mm larger than the bolt; distance between bolts along the grain about 7 to 8 diameters (4 for compression), end distance 7 diameters in tension, edge distance 1.5 to 4 diameters, spacing between rows 4 diameters.
• Details: washers prevent crushing; bolts are tightened again after seasoning of the timber; avoid bolts of very large diameter in thin members.