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Connection Failure Mode Explorer

AISC Limit States · Bolt Shear · Bearing · Tearout · Net Section · Block Shear

Connection FAILS
Bolt Shear governs, φRn = 53.7 kip < Ru = 80 kip (DCR = 1.49).

🔧 Connection Geometry & Load

Applied load Ru80 kip
Number of bolts n3
Plate thickness t0.375 in
Plate width (gross) Wp6 in
Edge distance Le1.5 in
Bolt spacing s3 in

📐 Connection Sketch

RuSingle-plate bolted connection (3 bolts)
AISC 360-16 Chapter J & D limit states for bolted connections. φ: bolt shear/bearing/tearout/net-fracture/block-shear = 0.75; gross yield = 0.90. The minimum φRn governs. Block shear tension area is approximated for a single bolt line — verify geometry for design. dh = db + 1/8 in (standard holes).
References
AISC 360-16 §J3.6 — bolt shear
§J3.10 — bearing & tearout
§J4.1 — tension yield/fracture
§J4.3 — block shear
§D2 — tension members
Governing Limit State
Bolt Shear
φRn = 53.7 kip · DCR = 1.49
6 / 6 revealed
Limit States — Ranked by φRn (ascending)
Limit StateφRn (kip)DCR
Bolt Shear◀ GOVERNS
AISC J3.6
53.71.49
Gross Section Yield
AISC J4.1 / D2
72.91.10
Net Section Fracture
AISC J4.1 / D2
83.60.96
Block Shear
AISC J4.3
87.40.92
Bolt Bearing
AISC J3.10
88.10.91
Bolt Tearout
AISC J3.10
104.00.77
DCR ≤ 0.75 0.75 < DCR ≤ 1.0 DCR > 1.0 (overstress)
Demand vs Capacity
Applied load Ru80 kip
Governing capacity φRn53.7 kip
Governing modeBolt Shear
Demand-Capacity Ratio1.49

Connection Failure Mode Explorer (AISC 360)

Explore all six AISC 360-16 limit states for a bolted steel connection: bolt shear, bolt bearing, bolt tearout, gross section yield, net section fracture, and block shear. The simulator ranks each limit state by capacity and identifies the governing failure mode with a demand-capacity ratio.

How It Works

Enter the applied shear Ru, bolt diameter, number of bolts, plate geometry, steel grade, and bolt grade. The calculator computes φRn for all six AISC Chapter J and D limit states simultaneously. Results are sorted by ascending capacity so the weakest (governing) mode is immediately visible. Step through limit states one by one to study how each failure mechanism controls.

Key Formulas

Bolt shear: φRn = 0.75·Fnv·Ab·n. Bolt bearing: φRn = 0.75·2.4·Fu·db·t·n. Tearout: φRn = 0.75·1.2·Fu·lc·t. Gross yield: φRn = 0.90·Fy·Ag. Net fracture: φRn = 0.75·Fu·An. Block shear: φRn = 0.75·min(0.6Fu·Anv + Ubs·Fu·Ant, 0.6Fy·Agv + Ubs·Fu·Ant). Standard hole diameter dh = db + 1/8 in.

When to Use

Use when sizing or checking bolted shear connections in steel construction such as beam-to-column shear tabs, clip angles, and gusset plates. All six limit states must be evaluated — the governing mode may change as bolt diameter, plate thickness, or edge distance changes. Always verify block shear geometry for your specific connection layout.

Frequently asked questions

What is block shear failure?

Block shear is a combined fracture-on-tension and shear-on-shear failure where a block of material tears out of the connection. It is computed as the minimum of two failure modes: shear fracture plus tension fracture, or shear yield plus tension fracture. AISC 360-16 §J4.3 governs.

What is the difference between bolt bearing and tearout?

Bearing failure (§J3.10) occurs when the bolt crushes the plate in bearing; capacity = 0.75·2.4·Fu·db·t per bolt. Tearout occurs when the bolt rips through the plate edge; capacity depends on the clear distance lc from the bolt hole edge to the plate edge. Tearout typically controls at small edge distances.

What does DCR mean?

DCR (Demand-Capacity Ratio) = Ru / φRn. A DCR ≤ 1.0 means the limit state passes. DCR > 1.0 means the applied load exceeds the design capacity for that mode. The governing limit state has the highest DCR.

Why is the resistance factor different for different limit states?

AISC assigns φ = 0.75 for fracture-type limit states (bolt shear, bearing, tearout, net section fracture, block shear) because fracture is sudden and non-ductile. Gross section yielding uses φ = 0.90 because it is a ductile limit state with greater post-yield reserve.

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