Steel Connection Design Checklist — Bolts, Welds, Plates

Q: What bolt checks are included in the connection checklist?

The bolt checklist covers: bolt shear strength (per AISC 360 J3-6), bearing strength at bolt holes (J3-6a), bolt tensile strength (J3-5), combined shear and tension (J3-3a/b), prying action (EC3 1-8 6.2.4), bolt pretension requirements (AISC Table J3.1), minimum and maximum spacing (J3-3, J3-4), edge distance (J3-4), and hole size limits (Table J3.3).

Q: What weld checks does the checklist cover?

The weld checklist covers: weld metal strength (AISC 360 J2-4), base metal strength (J2-2), minimum weld size (Table J2-4), maximum weld size (J2-2b), weld length limitations (J2-2b), intermittent weld requirements (J2-2c), end return welds (J2-2b), and electrode selection per matching requirements (AWS D1.1 Table 3.1).

Q: When are stiffeners required in steel connections?

Stiffeners are required when: (1) column web local yielding limits are exceeded per AISC 360 J10-2, (2) column web crippling limits per J10-5a/b, (3) column web compression buckling per J10-8, (4) panel zone shear exceeds φvRn per J10-11, or (5) flange bending stress exceeds the limit per J10-1. Stiffeners must be designed for the full unbalanced force and checked for local buckling themselves.

Q: What block shear checks are included?

Block shear checks per AISC 360 J4-3 (LRFD) and J4-3a (ASD): Rn = 0.6FuAnv + UbsFuAnt (tension rupture + shear rupture), with the limit that Rn ≤ 0.6FyAgv + UbsFuAnt (shear yielding + tension rupture). The checklist verifies block shear for gusset plates, shear tabs, end plates, beam copes, and column splices. The Ubs factor is 1.0 for uniform tension stress and 0.5 for non-uniform tension stress. The shear lag factor must be considered per AISC D3 for bolted connections.

Q: What is the difference between limit states for plates in tension and shear?

For tension plates per AISC 360 D2-2: yielding (φ=0.90, Ω=1.67) governs for gross section, and rupture (φ=0.75, Ω=2.00) governs for net section at bolt holes. For shear plates per J4-2: shear yielding (φ=1.0, Ω=1.50) uses 0.6FyAgv for gross shear area, and shear rupture (φ=0.75, Ω=2.00) uses 0.6FuAnv for net shear area. The checklist compares both limit states and flags the governing case, ensuring both gross and net sections are adequate for the design forces.

A comprehensive design checklist for structural steel connections covering bolted and welded connections, end plates, gusset plates, stiffeners, and connection detailing. Use as a QC review tool before finalizing connection designs.

Quick links: Bolted connections → | Welded connections → | Bolt torque →

Core calculations run via WebAssembly in your browser with step-by-step derivations across AISC 360, AS 4100, EN 1993, and CSA S16 design codes. Results are preliminary and must be verified by a licensed engineer.

Overview of Connection Design Checklists

A systematic connection design checklist ensures that all limit states are evaluated and that the connection satisfies strength, serviceability, and detailing requirements. Steel connection failures often result from overlooked limit states rather than inadequate member design — connections are typically the most highly stressed regions of a structure and contain the most complex detailing. The checklist approach breaks down the connection design into manageable checks organized by component: bolts, welds, connecting plates, and stiffeners.

Bolt Checks — Complete Coverage

Bolt Shear Strength

Per AISC 360 J3-6, the nominal shear strength of one bolt is Rn = Fnv × Ab, where Fnv is the nominal shear stress from Table J3.2 (54 ksi for A325-N, 68 ksi for A325-X, 45 ksi for A490-N, 60 ksi for A490-X) and Ab is the nominal bolt area (πd²/4). The design strength φRn uses φ = 0.75. For long joints exceeding 38 inches, the shear strength must be reduced per J3-7 by the factor C = 1.0 - (L - 38)/200 ≤ 1.0, where L is the total connection length in the direction of force.

Bearing and Tear-out at Bolt Holes

Per AISC 360 J3-6a, the nominal bearing strength for each bolt hole is the minimum of:

Rn = 1.2 × lc × t × Fu (tear-out failure at edge bolt)
Rn = 2.4 × d × t × Fu (bearing deformation limit of 0.25 inches)

For slotted holes, different coefficients apply (1.0 × lc × t × Fu for transverse loading of slots). The material properties (Fu) are those of the connected part, not the bolt.

Bolt Tensile Strength

Per J3-5, the nominal tensile strength of one bolt is Rn = Fnt × Ab, where Fnt is from Table J3.2 (90 ksi for A325, 113 ksi for A490). The design strength φRn uses φ = 0.75. Bolt tension governs in moment end plates, hanger connections, and tension splices.

Combined Shear and Tension

Per J3-3a and J3-3b, bolts subjected to combined shear and tension must satisfy: (fv/Fnv)² + (ft/Fnt)² ≤ 1.0 for LRFD (elliptical interaction), or the linear interaction per J3-3b for ASD. The allowable tensile stress is reduced when shear is present: F'nt = 1.3Fnt - (Fnt/φFnv)fv ≤ Fnt.

Block Shear

Per J4-3, block shear combines tensile rupture on one plane and shear rupture or yielding on the perpendicular plane. The nominal strength Rn = min(0.6Fu × Anv + Ubs × Fu × Ant, 0.6Fy × Agv + Ubs × Fu × Ant). The reduction factor Ubs = 1.0 for uniform tension stress, 0.5 for non-uniform tension (gusset plates with a single line of bolts).

Weld Checks — Complete Coverage

Weld Metal Strength

Per AISC 360 J2-4, the nominal strength of a fillet weld per unit length is Rn = 0.60 × FEXX × (0.707 × w) for LRFD, where FEXX is the electrode classification strength (70 ksi for E70 electrodes) and w is the weld leg size. The design strength φRn uses φ = 0.75. For ASD: Rn/Ω with Ω = 2.0. Weld strength increases for E80 (80 ksi), E90 (90 ksi), E100 (100 ksi), E110 (110 ksi), and E120 (120 ksi) electrodes.

Base Metal Strength

Per J2-2, the base metal adjacent to a welded joint must be checked for yielding. Rn = Fy × Abm (base metal yielding) and Rn = Fu × Abm (base metal rupture). The lower of weld metal and base metal strength governs the connection capacity. For complete joint penetration (CJP) groove welds, the weld is assumed to develop the full base metal strength and only the base metal needs to be checked.

Minimum and Maximum Weld Sizes

Per AISC Table J2-4, the minimum fillet weld size depends on the thickness of the thicker part joined: 1/8 inch for material up to 1/4 inch, 3/16 inch for 1/4 to 1/2 inch, 1/4 inch for 1/2 to 3/4 inch, 5/16 inch for 3/4 to 1-1/2 inches, and 3/8 inch for over 1-1/2 inches. Per J2-2b, the maximum fillet weld size along edges is: for material thickness < 1/4 inch, weld size = material thickness; for thickness ≥ 1/4 inch, weld size = material thickness - 1/16 inch.

Weld Length Limitations

Per J2-2b, the minimum length of fillet welds is 4 × weld size. Effective length cannot be less than 1.5 inches (40 mm). For longitudinal fillet welds longer than 100 × weld size, the effective length is reduced by the factor β = 1.2 - 0.002(L/w) ≤ 1.0.

Connecting Plate Checks

Plate Yielding (Tension)

Per J4-1, the nominal tensile yielding strength of a connecting plate is Rn = Fy × Ag, with φ = 0.90. This limit state checks against gross section yielding.

Plate Rupture (Tension)

Per J4-2, the nominal tensile rupture strength is Rn = Fu × Ae, with φ = 0.75. The effective net area Ae = An × U, where An is the net area deducting bolt holes and U is the shear lag factor from D3-1.

Block Shear on Plates

Same as block shear on bolts but evaluated on the connecting plate. This often governs for gusset plates and shear tabs with closely spaced bolts. The block shear path includes the shear planes along the bolt lines and the tension plane at the first bolt row.

Stiffener Requirements

Stiffeners are required at concentrated forces (beam-to-column connections, point loads on beams, column beam reactions) and panel zones (moment frame connections). The checklist evaluates:

Column web local yielding (J10-2) — For a force applied at a distance less than the column depth from the column end: Rn = (5.0 × k + N) × Fyw × tw. The available strength must exceed the applied force. If exceeded, web doubler plates are needed.

Column web crippling (J10-5) — For forces applied at or near the column top: Rn = 0.80 × tw² × [1 + 3 × (N/d) × (tw/tf)^1.5] × √(E × Fyw × tf/tw). If exceeded, transverse stiffeners opposite the beam flanges are required.

Panel zone shear (J10-11) — For moment frame connections, the panel zone (the column web region bounded by beam flanges) is checked for shear yielding. If insufficient, a doubler plate is added to increase the panel zone thickness. φ = 0.90 for panel zone shear.

Frequently Asked Questions

What bolt checks are included in the connection checklist? The bolt checklist covers: bolt shear strength (per AISC 360 J3-6), bearing strength at bolt holes (J3-6a), bolt tensile strength (J3-5), combined shear and tension (J3-3a/b), prying action (EC3 1-8 6.2.4), bolt pretension requirements (AISC Table J3.1), minimum and maximum spacing (J3-3, J3-4), edge distance (J3-4), and hole size limits (Table J3.3).

What weld checks does the checklist cover? The weld checklist covers: weld metal strength (AISC 360 J2-4), base metal strength (J2-2), minimum weld size (Table J2-4), maximum weld size (J2-2b), weld length limitations (J2-2b), intermittent weld requirements (J2-2c), end return welds (J2-2b), and electrode selection per matching requirements (AWS D1.1 Table 3.1).

When are stiffeners required in steel connections? Stiffeners are required when: (1) column web local yielding limits are exceeded per AISC 360 J10-2, (2) column web crippling limits per J10-5a/b, (3) column web compression buckling per J10-8, (4) panel zone shear exceeds φvRn per J10-11, or (5) flange bending stress exceeds the limit per J10-1. Stiffeners must be designed for the full unbalanced force and checked for local buckling themselves.

What block shear checks are included? Block shear is checked for both bolted and welded connections per AISC 360 J4-3. For bolted connections, the shear rupture path passes through the bolt holes, and the tension rupture path passes through the end distance. For welded connections, block shear is evaluated as weld group tear-out from the base metal. The Ubs factor accounts for stress non-uniformity: Ubs = 1.0 for symmetric tension, 0.5 for eccentric tension (typical of gusset plate connections). Block shear often governs for connections with short end distances or thin connecting plates.

What is the difference between limit states for plates in tension and shear? For plates loaded in tension, two limit states must be checked: (1) gross section yielding (φ = 0.90) — prevents excessive deformation at service loads, and (2) net section rupture (φ = 0.75) — prevents fracture failure at ultimate loads. For shear, the limit states are: (1) gross section shear yielding (φ = 1.0 for block shear), and (2) net section shear rupture (φ = 0.75). The lower φ factor for rupture reflects the more sudden nature of fracture failures compared to ductile yielding.

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This page is provided for general technical information and educational use only. It does not constitute professional engineering advice. All results must be independently verified by a licensed Professional Engineer.