Structural elements calculators
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Design of Wood Beams

Jonathan Ochshorn


Directions: Enter values for span (ft), spacing, species, grade, live and dead load (psf), duration of load and wet service conditions, allowable deflection criteria (e.g., span/360 for live load only), and select dimensions and properties from either the 2005 or 2012 National Design Specification (NDS). Updated design values for Southern Pine dimension lumber, effective June 1, 2013, are included with the 2012 NDS settings. Choose design criteria by entering "yes" or "no" in the appropriate cells. Press "update" button.

The two lightest sawn lumber sections for the 4 framing plan options shown below will be displayed. More detailed explanations and examples of wood beam design can be found in my text.

Note that the allowable stress method is used; only rectangular sawn lumber sections are tested; beams are assumed to be simply-supported and may be laterally-braced either continuously or only at the supports and point loads (if any).

Four plan types are included for each selection of beam span and spacing, as shown in the framing plans below:

sketch showing building dimensions
Fig. 1. Framing plans and load diagrams: a) uniformly-distributed load; b) single concentrated load at midspan; c) concentrated loads at third-points; and d) concentrated loads at quarter-points