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:

Zadjusted design value for lateral loading

Znominal design value for lateral loading

Wadjusted design value for withdrawal

Wnominal design value for withdrawal

Padjusted value for loading parallel to grain

Pnominal value for loading parallel to grain

Qadjusted value for loading normal to grain

Qnominal value for loading normal to grain

For bolts,

(6.39)

whereCDload-duration factor, not to exceed 1.6 for connections
CMwet-service factor, not applicable to toenails loaded in withdrawal
Cttemperature factor
Cggroup-action factor
Cgeometry factor

For split-ring and shear-plate connectors,

(6.40)

(6.41)

whereCdis the penetration-depth factor and Cstis the metal-side-plate factor.
For nails and spikes,

(6.42)

(6.43)

whereCdiis the diaphragm factor and Ctntoenail factor.

ZZCDCMCtCdCegCdiCtn

WWCDCMCtCtn

QQCDCMCtCgCCd

PPCDCMCtCgCCdCst

ZZCDCMCtCgC