Free Steel Bolted Connection Calculator — AISC 360 Design
Calculate the design strength of bolted connections in structural steelwork. The calculator checks bolt shear capacity (threaded and unthreaded), bearing strength of connected plies, tear-out failure, block shear rupture, and combined tension-plus-shear interaction bolts per AISC 360-22 Chapter J, AS 4100 Section 9, EN 1993-1-8, and CSA S16 Section 13.
Common connections: single-plate shear tabs, end-plate moment connections, gusset plate connections, splice plates, and framed beam connections. Bolt sizes range from 1/2-inch to 1-1/2-inch diameter in A325, A490, Grade 8.8, and Grade 10.9.
How to Use
- Configure bolt diameter, grade, thread condition (N or X), and bolt count.
- Set ply materials and thicknesses for bearing and tear-out checks.
- Specify connection geometry: end distance, edge distance, bolt spacing, pitch.
- Apply factored loads: shear, tension, or combined at the connection interface.
- Review results: utilization ratios for shear, bearing, tear-out, block shear, and interaction.
Design Code Requirements
| Check | AISC 360-22 Ch J | AS 4100 | EN 1993-1-8 | CSA S16-19 |
|---|---|---|---|---|
| Bolt shear | J3.6 (phi=0.75) | Cl 9.3.2.1 (phi=0.8) | Table 3.4 (gamma_M2=1.25) | Cl 13.12.1.2 |
| Bolt tension | J3.7 (phi=0.75) | Cl 9.3.2.2 (phi=0.8) | Table 3.4 | Cl 13.12.1.3 |
| Combined tension+shear | J3.7 (Eq J3-3a/b) | Cl 9.3.2.3 | Cl 3.6.1 (Table 3.4) | Cl 13.12.1.4 |
| Bearing/tear-out | J3.10 | Cl 9.3.2.4 | Cl 3.6.1 (Table 3.4) | Cl 13.12.1.4 |
| Block shear | J4.3 | Cl 9.3.2.5 | Cl 3.10.2 | Cl 13.11 |
Bolt Grades and Capacities
| Bolt | Diameter Range | Fnt (ksi) | Fnv (ksi) | Typical Use |
|---|---|---|---|---|
| A325 (Gr 8.8) | 1/2 - 1-1/2 | 90 (95 for X) | 54 (68 for X) | Standard steel frames |
| A490 (Gr 10.9) | 1/2 - 1-1/2 | 113 (113 for X) | 60 (78 for X) | Heavy connections |
| ASTM A307 | 1/2 - 4 | 45 | 27 | Light framing |
Step-by-Step Example
Problem: Check a bolted shear connection. (4) 3/4-inch A325-N bolts in single shear, connecting a W16x40 beam web (tw=0.305 in, Fy=50 ksi, Fu=65 ksi) to a 3/8-inch shear tab (A36, Fu=58 ksi). Factored shear demand Vu = 50 kips.
Step 1 — Shear per bolt (AISC 360-22 Eq J3-1): Rn = Fnv _ Ab = 54 _ 0.442 = 23.9 kips phi*Rn = 0.75 * 23.9 = 17.9 kips per bolt Group: 4 * 17.9 = 71.6 kips. Utilization: 50/71.6 = 0.70.
Step 2 — Bearing at bolt holes (AISC 360-22 Eq J3-6a): Tab (3/8 A36): Lc = 1.5 - 0.5*(0.75+1/16) = 1.09 in Rn = 2.4 * d _ t _ Fu = 2.4 _ 0.75 _ 0.375 _ 58 = 39.2 kips Rn from tear-out: 1.2 _ Lc _ t _ Fu = 1.2 _ 1.09 _ 0.375 * 58 = 28.5 kips phi*Rn = 0.75 * 28.5 = 21.4 kips per bolt — governs over shear.
Step 3 — Block shear (AISC 360-22 Eq J4-5): Lv = 6.0 in (vertical shear planes), Ant = 1.5 in^2 (net tension area) Rn = 0.6FuAnv + UbsFuAnt = 0.6582.25 + 1.0581.5 = 78.3 + 87 = 165.3 kips phi*Rn = 0.75 * 165.3 = 124 kips. OK.
Result: Utilization = 0.70 (shear in bolts), bearing OK at 0.52, block shear OK at 0.40. Connection passes.
Frequently Asked Questions
What is the difference between bolt shear strength and bearing strength? Bolt shear strength is the capacity of the bolt itself to resist shear across its cross-section, governed by bolt grade (Fnv) and gross area (Ab). Bearing strength is the capacity of the connected plies to resist crushing around the bolt hole, governed by edge distance, ply thickness, and steel tensile strength (Fu). Both must be checked — bearing often governs in thin-plate connections.
What is block shear, and when does it govern? Block shear is a combined rupture failure where a block of material tears out along a shear plane and tension plane simultaneously, governed by AISC 360-22 Eq J4-5. It typically governs in connections with short edge distances, thin gusset plates, or closely spaced bolts near an edge. Checking block shear is mandatory for all bolted connection designs.
How does thread condition (N vs X) affect bolt capacity? Thread condition determines the shear plane location. In N (threads included) connections, the shear plane passes through the threaded portion of the bolt, reducing shear capacity because the root area is smaller. In X (threads excluded) connections, the shear plane passes through the unthreaded shank, giving higher capacity. For A325 bolts, Fnv = 54 ksi (N) vs 68 ksi (X) — a 26% increase for X connections.
Which design standards cover bolted connections? AISC 360-22 Chapter J in the US, AS 4100 Section 9 in Australia, EN 1993-1-8 in Europe, and CSA S16 Section 13 in Canada. All four check similar limit states — bolt shear, bearing, tear-out, block shear — but differ in resistance factors and combined interaction equations.
Is this bolted connection calculator free? Yes, completely free with unlimited calculations. No registration needed.
Related pages
- Bolt bearing and tear-out reference
- Bolt spacing reference
- Steel connection checks
- Tension member design
- Base plate design
Disclaimer (educational use only)
This page is provided for general technical information and educational use only. It does not constitute professional engineering advice. All structural designs must be verified by a licensed Professional Engineer (PE) or Structural Engineer (SE). The site operator disclaims liability for any loss or damage arising from the use of this page.