United States15th and 16th edition (ASD)
Analyze steel bolt groups under combined in-plane shear and moment per AISC ASD. The elastic method distributes loads to each bolt using the polar moment of inertia, identifying the critical bolt demand across multiple load combinations in a single run.
Method & scope
What it calculates
US structural engineers analyzing bolted steel connections under combined load combinations per AISC ASD. Handles arbitrary bolt group geometry with multiple in-plane shear and moment inputs in a single calculation. Analyze bolt groups under combined load cases directly, removing the hand combinations required in the free version.Calculation method
The Steel Bolt Group Analysis (ASD) calculator applies the elastic method from the AISC Steel Construction Manual to determine the maximum shear demand on any bolt in an arbitrarily arranged bolt group subjected to in-plane shear and moment loads.Bolt group geometry
Bolt positions are defined by their X and Y coordinates. The centroid of the bolt group is calculated assuming all bolts have equal tributary area:- x_c = (sum of all x_i) / n
- y_c = (sum of all y_i) / n
Moment of inertia
The polar moment of inertia I_z (in^2, treating each bolt as a unit area) is the sum of squared distances from all bolts to the centroid: I_z = I_x + I_y = sum(y_i^2) + sum(x_i^2) This is used to distribute the torsional component of applied moment to each bolt location.Load distribution
For a bolt group loaded by a vertical shear V and an in-plane moment M (which may arise from an eccentrically applied load), the elastic method distributes forces as follows: Direct shear (vertical, shared equally):- V_p = V / n
- Vertical component: V_e = M × x_i / I_z
- Horizontal component: H_e = M × y_i / I_z
- V_t = V_p + V_e (total vertical shear)
- H_t = H_e (total horizontal shear)
- Resultant: R = sqrt(V_t^2 + H_t^2)
Critical bolt identification
The calculator evaluates R at every bolt in the group. The maximum resultant R governs the connection design. Utilization = R / R_allowable ≤ 1.0 where R_allowable is the allowable shear strength per bolt (to be specified by the engineer based on bolt grade, diameter, and connection type per AISC Tables).Multiple load cases
The ASD version supports multiple applied load combinations in a single run, each case is analyzed against the bolt group geometry, and the governing (maximum) bolt demand is reported. This removes the need to manually process each combination separately.Eccentricity
When the load is applied at an offset from the bolt group centroid, the eccentricity e is the horizontal distance from the load line to the centroid. The moment input M can be entered directly or derived from the product of shear force and eccentricity.How to use it
1
Open the calculator
Open it from Run calc in the About this calculator panel above.
2
Enter your inputs
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See Checks, References, Conditions and Assumptions.
3
Review the results and export
Check the utilization of each governing check in the summary, then export a PDF report. See Views and Export.
Steel Bolt Group Analysis: Overview
Steel Bolt Group Analysis (ASD): Example
Common questions
What design method and code does this calculator use?
What design method and code does this calculator use?
The calculator uses the elastic method per the AISC Steel Construction Manual (15th and 16th edition, ASD). It distributes applied shear and moment loads to each bolt using the polar moment of inertia of the bolt group, then identifies the critical bolt as the one carrying the highest resultant force.
What are the key inputs?
What are the key inputs?
Inputs include the bolt group geometry (X and Y coordinates for each bolt), the applied in-plane shear forces, and the moment and eccentricity of the load relative to the bolt group centroid. Multiple load cases can be applied simultaneously in the ASD version.
What does the calculator output?
What does the calculator output?
The key output is the maximum resultant shear force on the most heavily loaded bolt in the group (R, in kips). This value is compared against the bolt allowable shear capacity to determine if the connection is adequate. The polar moment of inertia and individual shear force components are also shown for verification.
Can it handle bolt groups under combined shear and moment?
Can it handle bolt groups under combined shear and moment?
Yes. The calculator resolves the applied shear and in-plane moment into direct shear and torsional shear components at each bolt location. The horizontal and vertical components are combined vectorially to give the resultant force on the most critical bolt.
What bolt grades and types are supported?
What bolt grades and types are supported?
This is an analysis-only calculator, it determines the force demand on the critical bolt but does not perform the bolt capacity check itself. The resultant demand R can be compared against the allowable bolt shear capacity for A325, A490, or other AISC-listed bolt grades as specified by the engineer.
Next steps
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