Description

This verification example utilizes Tekla Tedds to check the capacity of two interior wood columns with concentric compression loads. This example is based on Design Example E1.4 of 2015/2018 Structural Wood Design Examples by American Wood Council (AWC) (pages 23 to 27). Comparisons and contrasts are tabularized and discussed regarding the results from Tedds and the AWC Design Example. The Tedds file used in this example is provided in the Tedds “Select Calculation” window, under Verification Examples.

Problem statement

Compare the axial compression capacity of a nominal 4x4 and nominal 6x6 post being used for an interior column (only carrying gravity loads - dead load (DL) + floor live load (LL)). Both members are No. 2 Southern Pine and have a length of 10 feet. Both ends are assumed to be pinned (K_e = 1.0 - NDS 3.7.1.2). Assume all members are loaded concentrically.

References

2015/2018 Structural Wood Design Examples by American Wood Council

2018 National Design Specification for Wood Construction

Tedds calculation

Wood member design (NDS 2018) - Compared using version 2.2.29

Example information

Wood column information:

Sizes: 4x4 (nominal) and 6x6 (nominal)

Species: Southern Pine No. 2

Bearing length = 6”

Unbraced length - major and minor axis = 10’-0”

Buckling length factor - major and minor axis, K_e = 1.0

Reference and Adjusted Design Values:

4x4 post

F_c = 1,450 psi

E = E’ = 1,400,000 psi

E_min = E’_min = 510,000 psi

6x6 post

F_c = 525 psi

E = E’ = 1,200,000 psi

E_min = E’_min = 440,000 psi

C_D = 1.0

C_M = 1.0

C_t = 1.0

C_T = 1.0

C_i = 1.0

C_F = 1.0

Conclusion:

Upon reviewing the results above, the axial capacities of 4x4 and 6x6 wood columns using Tekla Tedds are consistent with the results of AWC Design Example E1.4. Users should feel confident that results determined in the Tedds Wood Member Design module are in agreement with NDS.