Eccentrically Loaded Bolt Group Software
The SkyCiv Eccentrically Loaded Bolt Group Software is intended for the analysis and design of bolt groups subjected to eccentric shear loading, in accordance with the AISC Construction Manual, 15th Edition (Tables 7-6 through 7-13) and the AISC 360-22 Specification for Structural Steel Buildings. This tool calculates the C coefficient for bolt groups and supports connection design using both LRFD and ASD methodologies.
The general procedure implemented in the calculator is based on the Brandt approximation for locating the Instantaneous Center of rotation (IC), as described in “Rapid Determination of Ultimate Strength of Eccentrically Loaded Bolt Groups” (1982). This method offers a reliable and practical approach to assessing the distribution of forces within bolt groups.
The program supports square and rectangular bolt patterns and calculates the C coefficient for applied eccentric shear loads. By inputting basic design parameters, engineers can rapidly evaluate the adequacy of bolt group configurations and verify compliance with AISC provisions. The eccentrically loaded bolt group tool is part of the SkyCiv Quick Design Module.
About the Bolt Group Coefficent Calculator
Eccentrically Loaded Bolt Group Design Metholodogy
The calculator requires the following inputs from the user:
- Design methodology (LRFD or ASD)
- Number of rows and columns of bolts
- Force location (referenced to either the bolt group’s center of gravity or the bottom-left corner)
- Force angle (measured with respect to the vertical alignment)
- Applied force magnitude
- Bolt size and material quality
- Connection type (single shear or double shear)
Based on these inputs, the tool computes the Instantaneous Center of rotation and evaluates the C coefficient, which is then used to determine the group’s design strength according to AISC requirements. You can read more of the ICOR method for bolt groups with this resource here.
Eccentrically Loaded Bolt Group Design Assumptions
The following assumptions are incorporated in the calculations:
- Bolt deformation is proportional to the distance from the Instantaneous Center of Rotation.
- Bolt behavior follows plastic deformation assumptions outlined in the AISC Construction Manual.
- The Brandt approximation is a valid and sufficiently accurate method for practical engineering applications.
- Only square and rectangular bolt group arrangements are currently supported.
- Circular or irregular bolt patterns are not supported.
- The tool does not suggest bolt spacing or group geometry; these must be defined by the user.
- Mixed shear–tension load cases are outside the current scope.
Bolt Group Design Failures
If failures or unconservative results are obtained, users may apply the following strategies to the bolt group
- Increase the number of bolts in the group
- Adjust bolt spacing or configuration
- Change to higher-strength bolts or larger diameters
- Reconsider the connection design methodology
Calculation References
- American Institute of Steel Construction (AISC). Steel Construction Manual, 15th Edition.
- American Institute of Steel Construction (AISC). Specification for Structural Steel Buildings (AISC 360-22).
- Brandt, M. (1982). Rapid Determination of Ultimate Strength of Eccentrically Loaded Bolt Groups.
Related SkyCiv Software
SkyCiv offers a wide range of Cloud Structural Analysis and Engineering Design Software, including:
- SkyCiv Quick Design
- SkyCiv Connection Design
- Weld Group Capacity Software
- Bolt Group Capacity Software
- Bolted Splice Connection Calculator
- Column Splice Conneciton Calculator
- Horizontal Bracing Connection Calculator
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