WORLD FOR CIVIL

Adjustment Factors

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 F_b‘ for extreme-fiber bending is given by

F_b‘=F_bC_DC_MC_tC_LC_FC_VC_fuC_rC_cC_f

where
F_b= design value for extreme-fiber bending
C_D= load-duration factor
C_M =wet-service factor
CC_t =temperature factor

C_L =beam stability factor

C_F =size factor—applicable only to visually graded, sawn lumber and round timber flexural members

C_v =volume factor—applicable only to glued- laminated beams

C_fu= flat-use factor—applicable only to dimension- lumber beams 2 to 4 in (50.8 to 101.6 mm) thick and glued-laminated beams

C_r= repetitive-member factor—applicable only to dimension-lumber beams 2 to 4 in (50.8 to101.6 mm) thick

C_c =curvature factor—applicable only to curved portions of glued-laminated beams

C_f =form factor

For glued-laminated beams, use eitherC_L or C_c (whichever is smaller), not both.
The adjusted design value for tension F_t‘ is given by

F_t‘= F_tC_DC_MC_tC_F

where
F_t is the design value for tension.

For shear, the adjusted design value F_v‘ is computed from

F_v‘=F_vC_DC_MC_tC_H

where
F_v is the design value for shear and C_H is the shear stress factor ?1—permitted for F_vparallel to the grain for sawn lumber members.

For compression perpendicular to the grain, the adjusted

design value F_c1‘is obtained from

F_c1‘= F_c1C_DC_tC_b

where
F_c1is the design value for compression perpendicular to the grain and C_b is the bearing area factor.

For compression parallel to the grain, the adjusted design

value isF_c‘

given by

F_c‘= F_cC_DC_MC_tC_FC_p

where
F_c is the design value for compression parallel to grain and C_p is the column stability factor.

For end grain in bearing parallel to the grain, the adjusted design value, F_g‘ is computed from

F_g‘= F_gC_DC_t

where
F_g is the design value for end grain in bearing parallel to the grain.
The adjusted design value for modulus of elasticity, E’ is obtained from

E’= EC_MC_TC..

where E= design value for modulus of elasticity

C_T= buckling stiffness factor—applicable only to sawn-lumber truss compression chords 2*4 in(50.8*101.6 mm) or smaller, when subject to combined bending and axial compression and plywood sheathing 3 /8 in (9.5 mm) or more thick is nailed to the narrow face

C..= other appropriate adjustment factors