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Wood tension element capacity calculator

Jonathan Ochshorn

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Directions: Enter values for species, grade, cross section, and bolt geometry (for regular bolt grid only; staggered bolt geometries cannot be used in this calculator). Enter "load of shortest duration" to adjust allowable stresses for "duration of load." For live and dead load only, enter "live load." Wet service conditions only matter for allowable shear (in tear-out calculations). Bolts, if any, are normally inserted through the smaller cross-sectional dimension, t (in which case the question, "bolt length = t?" is answered, "yes"). Cross sections are checked for tension capacity on the net area and, if desired, for row and group tear-out. It is assumed that the tension force is applied parallel to grain. Select either the 2005 or 2012 version of the National Design Specification (NDS); revised Southern Pine design values for dimension lumber (effective June 1, 2013) are included with the 2012 NDS.

Bolt geometry and bolt capacity (see Fig. 1) are not checked; however, bolt spacing and end/edge distances that do not comply with NDS-2005 guidelines are noted. Southern Pine allowable stress values for dimension lumber are approximate, so that the so-called "size factor" (included in published Southern Pine values, but left out of the allowable stress values for other species) can be considered in a consistent manner.

Press "update" button.

More detailed explanations and examples can be found in my text.

bolt geometry in wood cross section
Fig. 1. Wood cross section stressed in tension, showing bolt geometry.

species section no. of rows (Rn) bolts per row (n1)
grade tension force bolt diameter wet service?
load of shortest duration bolt length = t? space betw rows (in.) Scrit (in.)
check for row and group tear-out? governing capacity  
grade doesn't exist  
force must be > 0  
net area must be > 0