How is bolt shear capacity calculated per AS 4100?

Per AS 4100:2020 Clause 9.3.2: Nominal shear capacity Vf = 0.62 * fuf * kr * (nn*Ac + nx*Ao). For M20 Grade 8.8 (fuf=830 MPa, Ac=225mm^2), single shear with threads intercepted (nn=1, nx=0), kr=1.0 (Lj<300mm): Vf = 0.62*830*1.0*(1*225) = 115,785 N = 115.8 kN per bolt. Capacity reduction factor phi=0.80 per Table 3.4. phi*Vf = 0.80*115.8 = 92.6 kN per bolt. For 4 bolts: 370.4 kN total.

What is the difference between threads included and excluded in shear plane per AS 4100?

Per AS 4100:2020 Clause 9.3.2.1: When threads are intercepted by the shear plane (nn shear planes), the tensile stress area Ac is used in the Vf formula. When threads are excluded from the shear plane (nx shear planes), the larger shank area Ao is used. For an M20 bolt: Ac=225mm^2, Ao=314mm^2. Threads excluded gives 39.6% higher shear capacity per bolt. Specifying 'threads excluded' requires careful bolt detailing to ensure the unthreaded shank spans the full shear interface. The more conservative assumption (threads intercepted) is used when detailing cannot guarantee thread exclusion.

How is bolt bearing capacity calculated per AS 4100?

Per AS 4100:2020 Clause 9.3.3.1: Nominal bearing capacity of a ply Vb = a * tp * fu, where a = min(ae, 3.2*d) for edge bolts and a = min(spacing, 3.2*d) for interior bolts. For M20 bolt with ae=30mm: a = min(30, 3.2*20=64) = 30mm. With tp=10mm, fu=440MPa: Vb = 30*10*440 = 132,000 N = 132.0 kN per bolt. Capacity reduction factor phi=0.90 per Table 3.4. phi*Vb = 0.90*132.0 = 118.8 kN per bolt. Bearing rarely governs over shear for Grade 8.8 bolts in Grade 300 plate at standard edge distances.

Is this verification valid for design use?

This verification demonstrates algorithmic accuracy — it does NOT certify the software for construction use. All Steel Calculator outputs are PRELIMINARY and must be independently verified by a licensed Professional Engineer (CPEng, RPEQ, or NER). The verification benchmarks compare against published Australian Steel Institute (ASI) design guides and the ASI Steel Connections Handbook worked examples. No software output may be used directly for construction without independent PE review.

AS 4100:2020 Bolted Connection — Verification Benchmark

Q: What is the difference between threads included and excluded in shear plane per AS 4100?

Per AS 4100:2020 Clause 9.3.2.1: When threads are intercepted by the shear plane (nn shear planes), the tensile stress area Ac is used in the Vf formula. When threads are excluded from the shear plane (nx shear planes), the larger shank area Ao is used. For an M20 bolt: Ac=225mm^2, Ao=314mm^2. Threads excluded gives 39.6% higher shear capacity per bolt. Specifying 'threads excluded' requires careful bolt detailing to ensure the unthreaded shank spans the full shear interface. The more conservative assumption (threads intercepted) is used when detailing cannot guarantee thread exclusion.

Q: How is bolt bearing capacity calculated per AS 4100?

Per AS 4100:2020 Clause 9.3.3.1: Nominal bearing capacity of a ply Vb = a * tp * fu, where a = min(ae, 3.2*d) for edge bolts and a = min(spacing, 3.2*d) for interior bolts. For M20 bolt with ae=30mm: a = min(30, 3.2*20=64) = 30mm. With tp=10mm, fu=440MPa: Vb = 30*10*440 = 132,000 N = 132.0 kN per bolt. Capacity reduction factor phi=0.90 per Table 3.4. phi*Vb = 0.90*132.0 = 118.8 kN per bolt. Bearing rarely governs over shear for Grade 8.8 bolts in Grade 300 plate at standard edge distances.

Q: Is this verification valid for design use?

This verification demonstrates algorithmic accuracy — it does NOT certify the software for construction use. All Steel Calculator outputs are PRELIMINARY and must be independently verified by a licensed Professional Engineer (CPEng, RPEQ, or NER). The verification benchmarks compare against published Australian Steel Institute (ASI) design guides and the ASI Steel Connections Handbook worked examples. No software output may be used directly for construction without independent PE review.

Complete hand calculation of a bolted lap splice connection to AS 4100:2020, showing bolt shear and bearing capacity. Hand calculation results compared against Steel Calculator WASM output.

PRELIMINARY — NOT FOR CONSTRUCTION. All results are for educational and reference use only. Must be independently verified by a licensed Professional Engineer (CPEng, RPEQ, or NER) before use in any project.

Problem Statement

Connection: Double-lap splice in tension, connecting two 10mm Grade 300 plates (fu = 440 MPa) Bolts: 4 x M20, Grade 8.8/S (structural bolt, snug-tight) Shear plane: Threads intercepted in shear plane (single shear per bolt) Objective: Determine the design shear capacity (phiVf) and bearing capacity (phiVb) per AS 4100:2020 Clauses 9.3.2 and 9.3.3

Bolt Properties — M20 Grade 8.8/S

Property	Value	Source
Nominal diameter, d	20 mm	—
Shank area, Ao	314 mm^2	pi * d^2 / 4
Tensile stress area, Ac	225 mm^2	AS 1275 (ISO 898-1)
Minimum tensile strength, fuf	830 MPa	Table 9.3.1 (Grade 8.8)
Length of joint, Lj	<300 mm	—
kr (length reduction factor)	1.0	Clause 9.3.2.1

Plate Properties — Grade 300, 10mm thick

Property	Value
Thickness, tp	10 mm
Ultimate tensile strength, fu	440 MPa
Edge distance, ae	30 mm
Bolt pitch (along force)	60 mm
Bolt gauge (perpendicular)	70 mm

Hand Calculation — AS 4100:2020

Step 1: Bolt Shear Capacity — Clause 9.3.2

For bolts with threads intercepted in the shear plane, the nominal shear capacity per bolt is:

Vf = 0.62 * fuf * kr * (nn * Ac + nx * Ao)

where:
  nn = 1 (number of shear planes with threads intercepted)
  nx = 0 (number of shear planes with threads excluded)

Vf = 0.62 * 830 * 1.0 * (1 * 225 + 0 * 314)
   = 0.62 * 830 * 225
   = 115,785 N per bolt
   = 115.8 kN per bolt

Per Table 3.4, the capacity reduction factor for bolts in shear: phi = 0.80.

phi * Vf = 0.80 * 115.8 = 92.6 kN per bolt

Total for 4 bolts:

phi * Vf_total = 4 * 92.6 = 370.4 kN

Step 2: Bearing Capacity — Clause 9.3.3

Per AS 4100:2020 Clause 9.3.3, the nominal bearing capacity of a ply at a bolt is:

Vb = a * tp * fu

where a = min(ae, 3.2 * d)

For this connection (4 bolts in a single row along the force direction, all are edge bolts):

ae = 30 mm >= 1.5 * d = 30 mm  ÃÂ¢ÃÂÃÂ  OK for standard edge
a = min(ae, 3.2 * d) = min(30, 3.2 * 20) = min(30, 64) = 30

Vb = a * tp * fu = 30 * 10 * 440 = 132,000 N = 132.0 kN

Capacity reduction factor for bearing per Table 3.4: phi = 0.90 (bearing on connected ply, deformation permitted at service load).

phi * Vb_per_bolt = 0.90 * 132.0 = 118.8 kN per bolt
phi * Vb_total = 4 * 118.8 = 475.2 kN

Step 3: Controlling Limit State

phi * Vf_total = 370.4 kN (bolt shear)
phi * Vb_total = 475.2 kN (ply bearing)

Controlling: Bolt shear at 370.4 kN (governed by the bolt cross-section)

For an applied design shear V* = 250 kN:

Utilization = 250 / 370.4 = 0.675  ÃÂ¢ÃÂÃÂ  PASS at 67.5%

Step 4: Ply in Tension — Clause 7.2

The connected ply must also be checked for tension capacity at the net section:

Net area: An = (plate width - n * d_hole) * tp
Assume plate width = 120 mm, hole diameter = 22 mm (M20 + 2mm clearance)

An = (120 - 2 * 22) * 10 = (120 - 44) * 10 = 76 * 10 = 760 mm^2

Nt = 0.85 * kt * An * fu
kt = 1.0 (no eccentricity)
phi * Nt = 0.90 * 0.85 * 1.0 * 760 * 440
         = 0.90 * 284,240
         = 255,800 N
         = 255.8 kN  ÃÂ¢ÃÂÃÂ  > 250 kN ÃÂ¢ÃÂÃÂ

WASM Output Comparison

The Steel Calculator WASM engine (AS 4100 region), run with identical inputs:

Quantity	Hand Calculation	WASM Output	Difference
Vf per bolt (kN)	115.8	115.79	0.01%
phi*Vf total (kN)	370.4	370.38	0.01%
Vb per bolt (kN)	132.0	132.00	0.00%
phi*Vb total (kN)	475.2	475.20	0.00%
Controlling mode	Bolt shear	Bolt shear	Match
phi*Nt (kN)	255.8	255.82	0.01%
Utilization	0.675	0.675	0.00%
Verdict	PASS	PASS	Match

All 8 quantities match within 0.01%. The AS 4100 bolt calculation in the WASM engine is exact — differences are limited to floating-point rounding in the last displayed digit.

Code References — AS 4100:2020

Clause	Title	Application
Table 3.4	Capacity reduction factors	phi = 0.80 for bolts, 0.90 for bearing, 0.90 for tension
9.3.2.1	Bolts in shear	Nominal shear capacity Vf equation
9.3.2.2	Length reduction factor kr	kr = 1.0 for Lj <= 300mm
9.3.3	Bolts in bearing	Bearing capacity of ply Vb
9.3.3.1	Bearing formula	Vb = atpfu with a = min(ae, 3.2*d)
7.2	Members in tension	Nt, kt factors, net section check
Table 9.3.1	Bolt properties	fuf = 830 MPa for Grade 8.8
9.3.4	Combined shear and tension	Elliptical interaction (not governing here)

How to Reproduce

Navigate to the Steel Calculator Bolted Connection tool
Select AS 4100:2020 as the design code
Configure: 4 x M20 Grade 8.8/S, 10mm Grade 300 plates, single shear, threads in plane
Enter applied shear V* = 250 kN
Click Calculate — the WASM engine computes the bolt group capacity

Each bolt failure mode is checked automatically: shear, bearing, tearout, combined shear + tension, and ply rupture.

Why Verification Matters

Every Steel Calculator calculation engine is verified against published worked examples from the Australian Steel Institute (ASI) design guides, the ASI Steel Connections Handbook, and independent hand calculations. These public benchmark pages provide reproducible evidence of accuracy.

Last verified: 2026-05-08. WASM version: core-wasm-v2 stage-5-connection-design. Tolerance standard: all quantities within 1.0% of hand calculation or published value. AS 4100:2020 edition used for verification.

Disclaimer: This content is for educational purposes only. Results must be verified by a licensed professional engineer. Steel Calculator provides preliminary design tools — NOT a substitute for professional engineering judgment.