Bolt Group Calculator for Construction Connections

Inputs

Bolt layout

Input mode

Pattern is centered about its own centroid.

Rows

Columns

Spacing X (mm)

Spacing Y (mm)

Shift X (mm)

Shift Y (mm)

Loads

Shear Vx (kN) Shear Vy (kN) In-plane moment Mz (kN·m)

Moment is about the bolt-group centroid.

Bolt capacity

Capacity method Allowable per bolt (kN)

Estimator inputs (generic)

Fu (MPa)

Area Ab (mm²)

Factor φ

Estimated (kN)

If uncertain, use a verified allowable value.

Example Data Table

Sample 2×2 group, 100 mm spacing, Vx=20 kN, Vy=10 kN, Mz=2.5 kN·m, allowable 30 kN per bolt.

Bolt #	X (mm)	Y (mm)	Fx (kN)	Fy (kN)	Resultant (kN)	Utilization
1	0	0	-7.500	12.500	14.577	0.486
2	100	0	-7.500	-7.500	10.607	0.354
3	0	100	17.500	12.500	21.506	0.717
4	100	100	17.500	-7.500	19.039	0.635

Numbers are illustrative and may vary with sign convention.

Formula Used

1) Direct shear shared equally

Fdx = Vx / n

Fdy = Vy / n

2) Compute centroid and relative coordinates

x̄ = (Σxi)/n, ȳ = (Σyi)/n

x'i = xi − x̄, y'i = yi − ȳ

3) Moment distribution constant

Σr² = Σ(x'² + y'²)

k = Mz / Σr²

Mz is converted from kN·m to kN·mm internally.

4) Moment-induced shear on each bolt

Fmx = −k · y'

Fmy = +k · x'

5) Resultant bolt shear

Fx = Fdx + Fmx

Fy = Fdy + Fmy

Fres = √(Fx² + Fy²)

Utilization = Fres / (allowable per bolt)

How to Use This Calculator

Choose Rectangular pattern for common bolt grids.
Enter rows, columns, and spacing in millimeters.
Use shifts if your bolt group origin is offset.
For irregular layouts, switch to Manual coordinates.
Enter Vx, Vy, and Mz using your chosen sign convention.
Provide an allowable shear per bolt, or use the estimator.
Press Calculate to see the table and summary above.
Export CSV or PDF for checks, submittals, or internal review.

Inputs

Example Data Table

Formula Used

How to Use This Calculator

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