Page 520 - Forensic Structural Engineering Handbook

TIMBER STRUCTURES 14.11

Splits and wood plug
from end of beam
at overstressed bolts
due to beam rotation

FIGURE 14.5 Beam rotation with bolts causes splitting and end failure.

nutted. However, the moment from the eccentric application of vertical load on the bolts being
resisted at the column needs to be considered. Also, in a deep connection, moisture reduction
in the beam can cause vertical shrinkage tending to split the beam, often relieved by vertically
slotted holes. A beam stretcher detail specified for a project, shown in Fig. 14.6, allows rota-
tion of the steel bar to substantially reduce splitting forces. A sufficiently large diameter shal-
low hole needs to be provided to clear the bolt head so it will not bear on the wood under load
along with appropriate end distance of the connectors from this hole.

Snug
fit

Counter bore for bolt head
loobe fit, double nut tight
Decayed beam
end removed
FIGURE 14.6 Beam stretcher detail.

When the forensic engineer observes timber connections that are splitting the timber or
preferable one that has not yet split, stitch clamps described in this chapter can be used to
repair or strengthen the connections.
Stiff connections are needed in some situations such as to provide transfer of shear
between laminations on a glulam or an attempt to make two beams act as one. (See the