Problem 4.30

 

ASD, No. 2 Hem-Fir, fully braced, bending around strong axis

 

Property (psi) Dimension
Lumber
(Table 4A)		 Timbers (Table 4D)
Beams &
Stringers		 Posts &
Timbers
bending stress Fb 850 675 575
tension stress parallel to grain Ft 525 350 375
shear stress parallel to grain Fv 150 140 140
compression stress perpendicular to grain Fc⊥ 405 405 405
compression stress parallel to grain Fc 1,300 500 575
modulus of elasticity (or MOE) E 1,300,000 1,100,000 1,100,000
modulus of elasticity for stability calculations Emin 470,000 400,000 400,000

 

 

Roof joists, 2x10 @ 16" OC, supporting roof sheathing, D+S

 

NDS Supplement table 4A

Cr = 1.15
CM = 1
CF = 1.1 for Fb, 1.1 for Ft, 1.0 for Fc
Cfu = 1

NDS Supplement section 2.3

CD = 1.15 (S)
Ct = 1

NDS Supplement section 3.3

CL = 1 (fully braced)

NDS Supplement section 3.7

CP = 1 (not a column)

NDS Supplement section 3.10

Cb = 1 (not enough info given)

NDS Supplement section 4.3

Ci = 1

NDS Supplement section 4.4

CT = 1 (not a truss)

 

Property Reference Design
Values (psi)
(Table 4A)		 Adjustment Factors (Table 4.3.1) Adjusted Design
Values (psi)
CD CM Ct CL CF Cfu Cr CP Ci CT Cb
bending stress Fb 850 1.15 1 1 1 1.1 1 1.15   1     1,237
tension stress parallel to grain Ft 525 1.15 1 1   1.1       1     664
shear stress parallel to grain Fv 150 1.15 1 1           1     173
compression stress perpendicular to grain Fc⊥ 405   1 1           1   1 405
compression stress parallel to grain Fc 1,300 1.15 1 1   1     1 1     1,495
modulus of elasticity (or MOE) E 1,300,000   1 1           1     1,300,000
modulus of elasticity for stability calculations Emin 470,000   1 1           1 1   470,000

 

 

6x14 (beams & stringers) with equipment (permanent) load

 

NDS Supplement table 4D

CF = (12/d)1/9 for Fb = (12/13.5)1/9 = 0.9870 for Fb
CM = 1

NDS Supplement section 2.3

CD = 0.9 (permanent)
Ct = 1

NDS Supplement section 3.3

CL = 1 (fully braced)

NDS Supplement section 3.7

CP = 1 (not a column)

NDS Supplement section 3.10

Cb = 1 (not enough info given)

NDS Supplement section 4.3

Ci = 1

NDS Supplement section 4.4

CT = 1 (not a truss)

 

Property Reference Design
Values (psi)
(Table 4A)		 Adjustment Factors (Table 4.3.1) Adjusted Design
Values (psi)
CD CM Ct CL CF Cfu Cr CP Ci CT Cb
bending stress Fb 675 0.9 1 1 1 0.9870 1 1   1     600
tension stress parallel to grain Ft 350 0.9 1 1   1       1     315
shear stress parallel to grain Fv 140 0.9 1 1           1     126
compression stress perpendicular to grain Fc⊥ 405   1 1           1   1 405
compression stress parallel to grain Fc 500 0.9 1 1   1     1 1     450
modulus of elasticity (or MOE) E 1,100,000   1 1           1     1,100,000
modulus of elasticity for stability calculations Emin 400,000   1 1           1 1   400,000

 

 

Roof purlins, 4x14 @ 8' OC, D+Lr

 

NDS Supplement table 4A

Cr = 1
CM = 1
CF = 1.0 for Fb, 0.9 for Ft, 0.9 for Fc
Cfu = 1

NDS Supplement section 2.3

CD = 1.25 (Lr)
Ct = 1

NDS Supplement section 3.3

CL = 1 (fully braced)

NDS Supplement section 3.7

CP = 1 (not a column)

NDS Supplement section 3.10

Cb = 1 (not enough info given)

NDS Supplement section 4.4

CT = 1 (not a truss)

 

Property Reference Design
Values (psi)
(Table 4A)		 Adjustment Factors (Table 4.3.1) Adjusted Design
Values (psi)
CD CM Ct CL CF Cfu Cr CP Ci CT Cb
bending stress Fb 850 1.25 1 1 1 1 1 1   1     1,063
tension stress parallel to grain Ft 525 1.25 1 1   0.9       1     591
shear stress parallel to grain Fv 150 1.25 1 1           1     188
compression stress perpendicular to grain Fc⊥ 405   1 1           1   1 405
compression stress parallel to grain Fc 1,300 1.25 1 1   0.9     1 1     1,463
modulus of elasticity (or MOE) E 1,300,000   1 1           1     1,300,000
modulus of elasticity for stability calculations Emin 470,000   1 1           1 1   470,000

 

 

Floor beams, 4x6 @ 4' OC, D+L, high humidity, >19% MC

 

NDS Supplement table 4A

Cr = 1
CM = 0.85 for Fb (but FbCF < 1150 so CM = 1 for Fb), 1.0 for Ft, 0.97 for Fv, 0.67 for Fc⊥, 0.8 for Fc, 0.9 for E and Emin
CF = 1.3 for Fb, 1.3 for Ft, 1.1 for Fc
Cfu = 1

NDS Supplement section 2.3

CD = 1 (L)
Ct = 1

NDS Supplement section 3.3

CL = 1 (fully braced)

NDS Supplement section 3.7

CP = 1 (not a column)

NDS Supplement section 3.10

Cb = 1 (not enough info given)

NDS Supplement section 4.4

CT = 1 (not a truss)

 

Property Reference Design
Values (psi)
(Table 4A)		 Adjustment Factors (Table 4.3.1) Adjusted Design
Values (psi)
CD CM Ct CL CF Cfu Cr CP Ci CT Cb
bending stress Fb 850 1 1 1 1 1.3 1 1   1     1,105
tension stress parallel to grain Ft 525 1 1 1   1.3       1     863
shear stress parallel to grain Fv 150 1 0.97 1           1     146
compression stress perpendicular to grain Fc⊥ 405   0.67 1           1   1 271
compression stress parallel to grain Fc 1,300 1 0.8 1   1.1     1 1     1,144
modulus of elasticity (or MOE) E 1,300,000   0.9 1           1     1,170,000
modulus of elasticity for stability calculations Emin 470,000   0.9 1           1 1   423,000