------------------- | ----------------- | -------------------- | ------------------------- | ------------ | | 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

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.

Design Guidance

Key Design Parameters

When performing structural steel design calculations, the following parameters govern the design:

• Material properties: Yield strength (Fy) and tensile strength (Fu) determine section capacity. For US projects, common grades include A992 (Fy=50 ksi) for W-shapes and A36 (Fy=36 ksi) for angles and plates.
• Design method: LRFD (Load and Resistance Factor Design) or ASD (Allowable Stress Design). LRFD applies load factors >1.0 and resistance factors <1.0 for consistent reliability across limit states.
• Load combinations: Per ASCE 7-22, the governing combination depends on the direction and magnitude of each load type. Typically 1.2D + 1.6L governs for gravity-dominated cases.
• Limit states: Strength (ultimate) and serviceability (deflection, vibration). Both must be checked per the applicable design code.
• Applicable codes: AISC 360-22 (US), EN 1993-1-1 (EU), AS 4100 (Australia), CSA S16 (Canada).

Design Procedure

1. Establish design criteria: code edition, material grade, design method (LRFD/ASD)
2. Determine loads and applicable load combinations
3. Analyze structure for internal forces (axial, shear, moment, torsion)
4. Check member strength for all applicable limit states
5. Verify serviceability criteria (deflection, drift, vibration)
6. Detail connections to transfer calculated forces

Worked Example

Problem: Design a structural element for the following conditions:

Span/Height: 15 ft | Load: 50 kips (factored) | Section: W12×65 (A992, Fy=50 ksi) | Code: AISC 360-22 LRFD

Solution:

• Demand: Pu = 50 kips (axial compression)
• Section properties: A = 19.1 in², rx = 5.28 in, ry = 3.02 in
• Slenderness: KL/r = 1.0 × 15 × 12 / 3.02 = 59.6 (controls about weak axis)
• Critical stress: Fcr per AISC Eq E3-2 (intermediate slenderness range)
• Design strength: φcPn = 0.9 × Fcr × Ag — Verify against applied load
• Interaction: Check combined forces per AISC Chapter H if applicable

Result: Section is adequate if φcPn ≥ Pu (50 kips).

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.