ORDEN PÚBLICO Y NORMAS MATERIALES IMPERATIVAS EN EL MARCO ARBITRAL
II. Orden público y normas materiales imperativas en el DIPr. Admisibilidad en las distintas fases del proceso arbitral
3. EL ORDEN PÚBLICO EN LA CRISIS DEL PARADIGMA NORMATIVO DEL DIPr
The basic flexural design value, multiplied by all appli-cable adjustment factors except CL, is
Fb¼ FbCMCFCD
The beam stability factor is given by NDS Sec. 3.3.3 as
CL¼1:0 þ F
The allowable flexural design value for the load applied to the narrow face is
F0b1¼ FbCMCFCDCL The actual edgewise bending stress is
fb1¼W L
The critical buckling design value in the plane of bend-ing for load applied to the narrow face is
FcE1¼0:822E0min
The moment magnification factor for axial compression and flexure with load applied to the narrow face is
Cm3¼ 1:0 fc
The interaction equation for bending load applied to the narrow face of the member and concentric axial com-pression load is given in NDS Sec. 3.9.2 as
fc F0c
2
þ fb1
F0b1Cm3 1:0 The left-hand side of the expression is
404 lbf
< 1:0 ½satisfactory
The post is adequate.
4. DESIGN FOR TENSION Nomenclature
A area of cross section –
CD load duration factor –
CF size factor for sawn lumber –
Ci incising factor –
Cm wet service factor –
Ct temperature factor –
E reference modulus of elasticity lbf/in2 E0 allowable modulus of elasticity lbf/in2 ft actual tension stress parallel to grain lbf/in2
F ratio of FbEto Fb –
Fb reference bending design value multiplied by all applicable
adjustment factors except CL lbf/in2 Fb reference bending design value
multiplied by all applicable
adjustment factors except CV lbf/in2 FbE critical buckling design value for
bending members –
Ft reference tension design value parallel
to grain lbf/in2
F0t allowable tension design value parallel
to grain lbf/in2
le effective length of compression member ft lu laterally unsupported length of beam ft RB slenderness ratio of bending member –
T tensile force on member lbf
D E S I G N O F W O O D S T R U C T U R E S
5-15
Wood
Axial Tension
The reference design values for tension parallel to the grain are tabulated in the NDS Supplements. Allowable design values are obtained by multiplying basic values by the applicable adjustment factors. As specified in NDS Sec. 3.8.2, tension perpendicular to the grain is to be avoided.
Example 5.10
The select structural 2 8 Douglas Fir-Larch bottom chord of a truss is axially loaded in tension as shown in the illustration. The governing load combination con-sists of dead load plus live load plus snow load, and the moisture content exceeds 19%. The self-weight of the chord may be neglected. At the end connections, the net area is Anet= 9.3 in2. Determine whether the member is adequate.
(not to scale) 4 ft
T 8000 lbf T 4 ft
d2 1.5 in
d1 7.25 in
Solution
The reference design value for tension, tabulated in NDS Supp. Table 4A, is
Ft ¼ 1000 lbf in2
The size factor for tensile load is obtained from NDS Supp. Table 4A as
CF ¼ 1:20
The load duration factor is obtained from NDS Table 2.3.2 as
CD¼ 1:5 ½snow load
The wet service factor for tensile load is obtained from NDS Supp. Table 4A as
CM ¼ 1:00
The allowable tension design value parallel to grain is F0t¼ FtCMCFCD
¼ 1000 lbf in2
ð1:0Þð1:2Þð1:15Þ
¼ 1380 lbf=in2
The actual tension stress on the net area of the chord is ft;net¼ T
Anet
¼8000 lbf 9:3 in2
¼ 860 lbf in2
< F0t ½satisfactory
The member is adequate.
Combined Axial Tension and Flexure
Members subjected to combined tension and flexural stresses caused by axial and transverse loading must satisfy the two expressions given in NDS Sec. 3.9.1 as
ft F0tþfb
Fb 1:0 ½NDS 3:9-1
fb ft
Fb 1:0 ½NDS 3:9-2
Example 5.11
The select structural 2 8 Douglas Fir-Larch bottom chord of a truss is loaded as shown in the illustration.
The governing load combination consists of dead load plus live load plus snow load, and the moisture content exceeds 19%. The chord is laterally braced at midlength about the weak axis, and the self-weight of the chord and bracing members may be neglected. Determine whether the member is adequate.
(not to scale) d2 4 ft
1.5 in
d1 7.25 in
W
400 lbf 4 ft
T
T 8000 lbf
Solution
The relevant details from Ex. 5.10 follow. The allowable tension design value parallel to the grain is
F0t¼ 1380 lbf in2
Wood
The actual tension stress on the gross area of the
The reference design values for bending and the modu-lus of elasticity for stability calculations, tabulated in NDS Supp. Table 4A, are
Fb¼ 1500 lbf in2 Emin¼ 0:69 106 lbf
in2
The applicable adjustment factors for the modulus of elasticity are the following. The wet service factor is
CM ¼ 0:9 ½NDS Supp: Table 4A
The temperature factor is
Ct ¼ 1:0 ½NDS Table 2:3:3
The incising factor is
Ci¼ 1:0 ½NDS Table 4:3:8
The adjusted modulus of elasticity for stability calcula-tions is
For a concentrated load with lateral restraint, both at midspan, the effective length is obtained from Fig. 5.1 as
le¼ 1:11lu
¼ ð1:11Þð4 ftÞ 12 in ft
¼ 53:28 in
The slenderness ratio is given by NDS Sec. 3.3.3 as
RB¼ ð53:28 inÞð7:25 inÞ
ð1:5 inÞ2 s
¼ 13:10
< 50 ½satisfies criteria of NDS Sec: 3:3:3
The critical buckling design value is FbE¼1:20E0min
The applicable adjustment factors for bending are the following. The wet service factor is
CM ¼ 0:85 ½NDS Supp: Table 4A
The size factor is
CF ¼ 1:2 ½NDS Supp: Table 4A
The load duration factor is
CD¼ 1:15 ½NDS Table 2:3:2
The reference flexural design value, multiplied by all applicable adjustment factors except CL, is
Fb¼ FbCMCFCD
The beam stability factor is given by NDS Sec. 3.3.3 as CL¼1:0 þ F
The reference flexural design value, multiplied by all applicable adjustment factors except CV, is
Fb ¼ FbCMCFCDCL
...
The actual edgewise bending stress is fb1¼W L
4S
¼ð400 lbfÞð8 ftÞ 12 in ft
ð4Þð13:14 in3Þ
¼ 731 lbf=in2
Substituting in the two expressions given in NDS Sec. 3.9.1 gives
ft F0tþfb1
Fb¼ 735 lbf in2 1380 lbf
in2
þ 731 lbf in2 1760 lbf
in2
¼ 0:533 þ 0:415
¼ 0:948
< 1:0 ½satisfactory
fb1 ft
Fb ¼731 lbf
in2 735 lbf in2 1707 lbf
in2
¼ 0:002
< 1:0 ½satisfactory
The chord is adequate.
5. DESIGN FOR SHEAR