Sawn Lumber Design

Sawn Lumber Design - Design Practices

Fig. 1: A sawn lumber design of a barn roof

Wood species and grades will greatly vary the strength of the member. Sawn Lumber is solid wood (as opposed to Glulams which are numerous pieces glued together. The size of the lumber will not be the exact size of the beam due to the planing and sanding necessary to get a finished product (e.g. a 2"x4" which is rather common is actually 1.5"x3.5").

Sawn Lumber Analysis

Analysing the stress acting on the member can be done from the Structural Analysis? section (it is no different than analysing the stress in other types of material). In order to find the allowable stress in a member you will have to go through the Sawn Lumber Adjustment Factors section below. Numerous examples on how to calculate out different factors has been provided for completeness.

• Sawn Lumber Adjustment Factors - Your Adjustment Factors for determining the adjusted design value of a member.
  • C_D = Load Duration Factor - ASD only
  • C_M = Wet Service Factor
  • C_t = Temperature Factor
  • C_L = Beam Stability Factor
  • C_F = Size Factor
  • C_fu = Flat Use Factor
  • C_i = Incising Factor
  • C_r = Repetitive Member Factor
  • C_P = Column Stability Factor
    • Column Stability Factor Example #1
  • C_T = Buckling Stiffness Factor
  • C_b = Bearing Area Factor
  • K_F = Format Conversion Factor - LRFD only
  • ø_var = Resistance Factor - LRFD only
  • λ = Time Effect Factor - LRFD only