CIVIL ENGINEERING FORMULAS

164 CHAPTER SIX

ADJUSTMENT FACTORS FOR DESIGN VALUES

Design values obtained by the methods described earlier should be multiplied by
adjustment factors based on conditions of use, geometry, and stability. The
adjustments are cumulative, unless specifically indicated in the following.
The adjusted design value for extreme-fiber bending is given by

FbCDCMCtCLCFCVCfuCrCcCf (6.19)

where Fbdesign value for extreme-fiber bending
CDload-duration factor
CMwet-service factor
Cttemperature factor
CLbeam stability factor
CFsize factor—applicable only to visually graded, sawn lumber and
round timber flexural members
Cvvolume factor—applicable only to glued-laminatedbeams
Cfuflat-use factor—applicable only to dimension-lumber beams 2 to
4 in (50.8 to 101.6 mm) thick and glued-laminated beams
Crrepetitive-member factor—applicable only to dimension-lumber
beams 2 to 4 in (50.8 to 101.6 mm) thick
Cccurvature factor—applicable only to curved portions of glued-
laminated beams
Cfform factor

For glued-laminated beams, use either CLorCv(whichever is smaller), not both.
The adjusted design value for tension is given by

(6.20)

whereFtis the design value for tension.

FtFtCDCMCtCF

Ft

Fb

Fb

M 2

M 1

B

F

b

f 2

f 1

φ/2

φ/2

φ

C

A

FIGURE 6.1 Timber joint.