Wood Column to NDS 2018 - Validation Examples

Validation and design examples for wood columns per NDS 2018. Note that values will vary slightly (+/- 1%) due to round-off errors.

Example 1 - Sawn Lumber Column using ASD and LRFD

Reference: Abi Aghayere and Jason Vigil, Structural Wood Design, 2nd Edition, 2017, Taylor & Francis, Example 5.6, p. 299

Inputs

Parameter Value
Column Size & Grade 6x6 D.Fir-L No. 1
Column Unbraced Lengths $L_x = L_y =$ 12' 
Service Conditions Dry, normal temperature
Axial Loads $D$ = 6,800 lb, $S$ = 10,200 lb, Self-weight not considered, No eccentricity

Outputs

Result Example (ASD/LRFD) ClearCalcs (ASD/LRFD)
Design Load 17,000 lb / 24,500 lb 17,000 lb / 24,500 lb
Buckling Stress $F_{cE}$ 695 psi / 1,042 psi 696 psi / 1040 psi
Column Stability Factor $C_p$ 0.502 / 0.502 0.503 / 0.501
Allowable Column Capacity* 17,463 lb / 26,300 lb 17,497 lb / 26,205 lb

Example 2 - Exterior Stud Wall Using ASD

Reference: Abi Aghayere and Jason Vigil, Structural Wood Design, 2nd Edition, 2017, Taylor & Francis, Example 5.9, p. 313

Inputs

Parameter Value
Column Size & Grade 2x6 D.Fir-L No. 2 @ 2' o.c.
Column Unbraced Lengths $L_x$ = 10',  $L_y =$ 0' (braced by sheathing for Y-axis buckling and lateral-torsional buckling)
Service Conditions Dry, normal temperature, repeating member
Axial Loads $D$ = 1,440 lb, $L$ = 640 lb, $S$ = 1,440 lb, Self-weight not considered, No Eccentricity
Lateral Loads $W$ = 25 psf (specified as $0.6W$ = 15 psf in the example)
   

Outputs

The example splits into 4 main design checks (the first one is ignored as it checks for net section bearing stress which is irrelevant in this case)

Design Check 2 - Pure Axial Loading and Bearing

Result Example ClearCalcs
Governing Load Case D + 0.75(L + S) D + 0.75(L + S)
Governing Axial Load 3,000 lb 3,000 lb
Column Stability Factor $C_p$
0.492 0.491
Allowable Compression Stress  840 psi 839 psi
Allowable Bearing Stress 625 psi 625 psi
Utilization Ratio * 43.3% 43.3%

*Since the example deals with stresses and ClearCalcs deals with loads, we compare the utilization ratio to show that the results are exactly the same.

Design Check 3 - Pure Bending

Result Example ClearCalcs
Governing Load Case D + 0.6W D + 0.6W
Governing Moment 4,500 in-lb = 375 lb-ft 375 lb-ft
Allowable Bending Stress 2,153 psi 2,153 psi
Utilization Ratio * 27.6% 27.6%
     

*Since the example deals with stresses and ClearCalcs deals with loads, we compare the utilization ratio to show that the results are exactly the same.

Design Check 4 - Combined Loading

Result Example ClearCalcs
Governing Load Case D + 0.75(L + S + 0.6W) D + 0.75(L + S + 0.6W)
Governing Axial Load 3,000 lb 3,000 lb
Governing Moment 3,375 lb-in = 281.25 lb-ft 281.25 lb-ft
Allowable Bending Stress 2,153 psi 2,153 psi
Column Stability Factor $C_p$ 0.377 0.376
Allowable Compression Stress 896 psi 894 psi
Interaction Equation 0.49 0.49
     

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