CIVIL ENGINEERING FORMULAS

TIMBER ENGINEERING FORMULAS 173

BENDING AND AXIAL TENSION

Members subjected to combined bending and axial tension should be propor-
tioned to satisfy the interaction equations

(6.53)

and

(6.54)

where fttensile stress due to axial tension acting alone
fbbending stress due to bending moment alone
design value for tension multiplied by applicable adjustment factors
design value for bending multiplied by applicable adjustment fac-
tors except CL
design value for bending multiplied by applicable adjustment factors
exceptCV

The load duration factor CDassociated with the load of shortest duration in a
combination of loads with differing duration may be used to calculate and

. All applicable load combinations should be evaluated to determine the criti-
cal load combination.

BENDING AND AXIAL COMPRESSION

Members subjected to a combination of bending and axial compression (beam
columns) should be proportioned to satisfy the interaction equation

(6.55)

where fccompressive stress due to axial compression acting alone

design value for compression parallel to grain multiplied by applic-

able adjustment factors, including the column stability factor

fb 1 bending stress for load applied to the narrow face of the member

fb 2 bending stress for load applied to the wide face of the member

design value for bending for load applied to the narrow face of the

member multiplied by applicable adjustment factors, including the

column stability factor

design value for bending for load applied to the wide face of the

member multiplied by applicable adjustment factors, including

the column stability factor

Fb 2

Fb 1

Fc



fb 2

[1(fc/FcE2)(fb 1 /FbE)^2 ]Fb 2

 1



fc

Fc

2



fb 1

[1(fc/FcE1)]Fb 1

Fb*

Ft

F**b

Fb*

Ft

(fbft)

F**b

 1

ft

Fc



fb

Fb*

 1