How to use the bolt bearing strength calculator
Bearing strength at a bolt hole follows AISC 360-16 Section J3.10. For a standard hole where deformation at service load is a design consideration, the nominal strength per bolt is Rn = 1.2·Lc·t·Fu with an upper bound of 2.4·d·t·Fu. Lc is the clear distance from the edge of the hole to the next hole or to the edge of the plate: edge distance minus half the hole diameter for an end bolt, and spacing minus one hole diameter for an interior bolt. Standard hole sizes are taken as d + 1/16 in up to 7/8 in bolts and d + 1/8 in above that.
Two checks come out of one formula. When Lc is short the tearout term governs and the strength is proportional to the clear distance, so a bolt at a 1-1/4 in edge distance carries far less than an interior bolt at 3 in spacing. Once Lc is long enough the 2.4·d·t·Fu crushing limit caps the value. The tool reports the end bolt and interior bolts separately, adds them into a bolt group total, and multiplies by φ = 0.75 for LRFD; for ASD divide the nominal value by Ω = 2.00 instead.
Bearing is only one of several limit states in a bolted connection. Bolt shear, tensile yielding and rupture of the connected part, block shear rupture, and slip resistance in slip-critical joints all have to be checked, and the smallest value governs. Minimum spacing of 2-2/3 d (3d preferred) and the minimum edge distances in AISC Table J3.4 must also be satisfied, and oversized or slotted holes change the hole dimensions. Have a licensed structural engineer review connections that carry primary load.
Frequently Asked Questions
They are two limit states combined into one expression, and the lower value controls. The 1.2·Lc·t·Fu term is tearout of the material ahead of the hole, while 2.4·d·t·Fu is the upper bound set by crushing at the hole. AISC 360-22 lists them as separate sections, J3.11 and J3.12, with the same numbers.
No. The Fu in the equation is the tensile strength of the connected plate, not the bolt, so an A490 bolt in a thin A36 plate gives the same bearing value as an A325 bolt. Bolt grade matters for the separate bolt shear and tension checks.