Solved Example: Design of Sawn Timber Column

Articles > Solved Example: Design of Sawn Timber Column

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Question:

Design data:

Floor area supported by column:  A = 80 ft²

Unsupported length of column, L = 10 ft

Hinge support at top and bottom of column

Design load:

Floor live load: W_L = 30 psf

Floor dead load: W_D = 10 psf

Superimposed dead load: W_SD = 5 psf

Timber: Southern pine, moisture less than 19%, used in normal room temperature.

 

Solution:

Refer to Design of Sawn Timber Columns and Compressive Members article for concepts.

1. Select southern pine, 4"x4" stud grade, d = 3.5 in

Actual cross section: A_c = 12.25 in2.

Allowable compressive stress parallel to grain: F_c = 975 psi

2. Calculate slenderness ratio: K_e = 1, L_e =K_e´L = 10 ft, L_e/d = 34 < 50

3. Calculate compressive stress with load duration factor

Load duration factor for dead load: C_D = 0.9

Load duration factors for live load: C_D = 1.0

Calculate Design load: P = [W_D + W_SD+ W_L]´A = 3600 lb

Column compressive stress, f_c=P/A_c = 293.8 psi

4. Calculate allowable stress without C_p.

C_M=1, C_t=1, C_f=1

F_c* = F_c´C_M´C_t´C_F = 975 psi

5. Calculate elasticity modulus

E’=E´CM´Ct = 1.4´10⁶ psi

6. Calculate F_cE

K_cE=0.3

F_cE= K_cE*E’/(L_e/d)²= 357.3 psi

7. Calculate C_p

c = 0.8

C_p = 0.333

8. Calculate allowable compressive stress

F”_c = F_c*´C_p = 324.8 psi               >          f_c= 293.8 psi     O.K.

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Read also:

• Design of Sawn Timber Columns and Compressive Members
• Solved Example: Design of Timber Load Bearing Stud Wall
• Design of Sawn Timber Beams or Joists
• Solved Example: Design of 2x10 Timber Floor Joist with Southern Pine
• Solved Example: Design of 3-3x12 Timber Beam with Southern Pine

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