Structural engineers engaged in steel design require detailed knowledge of the weld capacity of eccentric connections. This Excel sheet is built per the AISC-ASD 9th Edition and automates the tedious calculations for eccentric weld group design. Whether examining a beam-to-column connection or designing a bracket-type attachment, this tool properly and safely determines weld sizes under axial, shear, and moment loads.
What Is an Eccentric Weld Connection?
An eccentric connection is one where the applied load does not pass through the centroid of the weld group. This eccentricity introduces a torsional moment in addition to the direct shear force, causing unequal stress distribution across the weld group. Failure to account for eccentricity is a common source of under-designed connections in steel structures.
Common examples include shelf-plate brackets, lug plates, lifting lugs, and eccentric beam-end connections. These are encountered frequently in industrial structures, mezzanines, and equipment supports.
AISC-ASD 9th Edition Eccentric Weld Design Methods
The AISC-ASD 9th Edition provides two accepted methods for eccentric weld analysis:
- Elastic (Vector) Method: Conservatively treats the weld as an elastic line. Stresses from direct shear and torsion are combined vectorially at the most stressed point.
- Instantaneous Centre of Rotation (ICR) Method: More accurate. The weld group rotates about an instantaneous centre, and ductility allows force redistribution before failure. AISC tables are used to find the coefficient C for the specific geometry.
This sheet implements the elastic method which is the more straightforward approach and is conservative for design purposes.
What the Sheet Calculates
- Centroid of the weld group
- Polar moment of inertia of the weld (Ip)
- Direct shear stress component (fv)
- Torsional stress component (ft)
- Resultant stress at the critical weld point
- Required weld size comparison against allowable shear stress per AISC-ASD
Download Window Application Program
Download the Eccentric Weld Capacity Sheet (AISC-ASD 9th)
This sheet is used daily by steel connection designers who need a fast, reliable method to size welds in bracket and eccentric attachment configurations. The transparent calculation layout makes it easy to check and include in a formal steel connection design report. Download the free Excel sheet below.
