Page 239 - 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
f t f b
1 (6.53)
F c F b *
and
( f b f t )
1 (6.54)
**
F b
where f tensile stress due to axial tension acting alone
t
f bending stress due to bending moment alone
b
design value for tension multiplied by applicable adjustment factors
F t
*
F b design value for bending multiplied by applicable adjustment fac-
tors except C L
**
F b design value for bending multiplied by applicable adjustment factors
except C V
The load duration factor C associated with the load of shortest duration in a
D
and
combination of loads with differing duration may be used to calculate F t
*
F b . 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
2 f b1 (6.55)
f c
F c [1 ( f c /F cE1 )]F b1
f b2
1
2
[1 ( f c /F cE2 ) ( f b1 /F bE ) ]F b2
where f compressive stress due to axial compression acting alone
c
design value for compression parallel to grain multiplied by applic-
F c
able adjustment factors, including the column stability factor
f bending stress for load applied to the narrow face of the member
b1
f bending stress for load applied to the wide face of the member
b2
design value for bending for load applied to the narrow face of the
F b1
member multiplied by applicable adjustment factors, including the
column stability factor
design value for bending for load applied to the wide face of the
F b2
member multiplied by applicable adjustment factors, including
the column stability factor