Columns

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

ParameterValue
Column Size & Grade6x6 D.Fir-L No. 1
Column Unbraced Lengths L x = L y = L_x = L_y = 12'
Service ConditionsDry, normal temperature
Axial Loads D D = 6,800 lb, S S = 10,200 lb, Self-weight not considered, No eccentricity

Outputs

ResultExample (ASD/LRFD)ClearCalcs (ASD/LRFD)
Design Load17,000 lb / 24,500 lb17,000 lb / 24,500 lb
Buckling Stress F c E F_{cE} 695 psi / 1,042 psi696 psi / 1040 psi
Column Stability Factor C p C_p 0.502 / 0.5020.503 / 0.501
Allowable Column Capacity*17,463 lb / 26,300 lb17,497 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

ParameterValue
Column Size & Grade2x6 D.Fir-L No. 2 @ 2' o.c.
Column Unbraced Lengths L x L_x = 10', L y = L_y = 0' (braced by sheathing for Y-axis buckling and lateral-torsional buckling)
Service ConditionsDry, normal temperature, repeating member
Axial Loads D D = 1,440 lb, L L = 640 lb, S S = 1,440 lb, Self-weight not considered, No Eccentricity
Lateral Loads W W = 25 psf (specified as 0.6 W 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

ResultExampleClearCalcs
Governing Load CaseD + 0.75(L + S)D + 0.75(L + S)
Governing Axial Load3,000 lb3,000 lb
Column Stability Factor C p C_p 0.4920.491
Allowable Compression Stress840 psi839 psi
Allowable Bearing Stress625 psi625 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

ResultExampleClearCalcs
Governing Load CaseD + 0.6WD + 0.6W
Governing Moment4,500 in-lb = 375 lb-ft375 lb-ft
Allowable Bending Stress2,153 psi2,153 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

ResultExampleClearCalcs
Governing Load CaseD + 0.75(L + S + 0.6W)D + 0.75(L + S + 0.6W)
Governing Axial Load3,000 lb3,000 lb
Governing Moment3,375 lb-in = 281.25 lb-ft281.25 lb-ft
Allowable Bending Stress2,153 psi2,153 psi
Column Stability Factor C p C_p 0.3770.376
Allowable Compression Stress896 psi894 psi
Interaction Equation0.490.49

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