Bolts are installed in holes drilled slightly (1.0 to 2.0mm (1/32″ to 1/16″) larger than the bolt diameter to prevent any splitting and stress development that could be caused by installation or subsequent wood shrinkage.
Wood shrinkage requires special consideration in the design of bolted connections for sawn timber because of the potential high moisture content of the members. It is less important in designing connections for glulam, PSL, or other wooden products manufactured at low moisture control.
As shrinkage across the grain takes place in timber, movement may be restrained by the steel side plates leading to splitting of the wood. If steel side plates hold bolts further than 125mm (5″) apart across the width in a splice joint, separate side plates should be used as in Figure 5.12 below.
Figure 5.12: Types of Bolted Splices