Page 237 - Civil Engineering Formulas

TIMBER ENGINEERING FORMULAS 171

The allowable lateral load for wood screws driven into end grain is two-thirds
that given for side grain.

ADJUSTMENT OF DESIGN VALUES FOR CONNECTIONS
WITH FASTENERS

Nominal design values for connections or wood members with fasteners should
be multiplied by applicable adjustment factors available from lumber associations
and in civil engineering handbooks to obtain adjusted design values. The types of
loading on the fasteners may be divided into four classes: lateral loading, with-
drawal, loading parallel to grain, and loading perpendicular to grain. Adjusted
design values are given in terms of nominal design values and adjustment factors
in the equations below. The following variables are used in the equations:
Z adjusted design value for lateral loading
Z nominal design value for lateral loading
W adjusted design value for withdrawal
W nominal design value for withdrawal
P adjusted value for loading parallel to grain
P nominal value for loading parallel to grain
Q adjusted value for loading normal to grain
Q nominal value for loading normal to grain

For bolts,
Z ZC D C M C t C g C (6.39)
where C load-duration factor, not to exceed 1.6 for connections
D
C wet-service factor, not applicable to toenails loaded in withdrawal
M
C temperature factor
t
C group-action factor
g
C geometry factor

For split-ring and shear-plate connectors,
P PC D C M C t C g C C d C st (6.40)
(6.41)
Q QC D C M C t C g C C d
where C is the penetration-depth factor and C is the metal-side-plate factor.
st
d
For nails and spikes,
W WC D C M C t C tn (6.42)
Z ZC D C M C t C d C eg C di C tn (6.43)
where C is the diaphragm factor and C toenail factor.
di
tn