# Wood tension element capacity calculator

Jonathan Ochshorn

contact | academic homepage | Structural Elements for Architects and Builders | calculator homepage

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.

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

 species section no. of rows (Rn) bolts per row (n1) Douglas Fir-Larch Douglas Fir-Larch (North) Douglas Fir-South Hem-Fir Hem-Fir (North) Spruce-Pine-Fir Spruce-Pine-Fir (South) Southern Pine 2x4 2x6 2x8 2x10 2x12 4x4 4x6 4x8 4x10 4x12 6x10 6x12 6x14 6x16 6x18 6x20 8x12 8x14 8x16 8x18 8x20 10x14 10x16 10x18 12x16 12x18 12x20 14x18 14x20 16x20 6x6 6x8 8x8 8x10 10x10 10x12 12x12 12x14 14x14 14x16 16x16 16x18 18x18 18x20 0 1 2 3 4 5 6 0 1 2 3 4 5 6 7 8 9 10 11 12 grade tension force bolt diameter wet service? Select Structural No. 1 No. 2 No. 3 Misc. 1/4 in. 3/8 in. 1/2 in. 5/8 in. 3/4 in. 7/8 in. 1 in. yes no lb kips load of shortest duration bolt length = t? space betw rows (in.) Scrit (in.) Dead load, D Live load, L Snow load, S Construction load, Lr Wind or seismic load, W or E Impact load, I yes no 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 check for row and group tear-out? governing capacity based on 2005 NDS based on 2012 NDS yes no "" "" Checks: errors: grade doesn't exist force must be > 0 net area must be > 0