End Plate Connection — Moment Connection Design

Steel end plate moment connection design per AISC Design Guide 4. Bolt prying action, plate yielding, stiffener requirements, and column web checks. Educational use only.

This page documents the scope, inputs, outputs, and computational approach of the End Plate Connection tool on steelcalculator.app. The interactive calculator runs in your browser; this documentation ensures the page is useful even without JavaScript.

What this tool is for

Designing flush and extended end plate moment connections per AISC Design Guide 4.
Checking bolt prying forces, end plate bending, column flange bending, and column web yielding/crippling.
Determining stiffener and doubler plate requirements for the column panel zone.

What this tool is not for

It does not handle seismic prequalified connections per AISC 358 (though the limit states are similar).
It does not design the beam-to-end-plate weld or the column splice.
It does not check column web panel zone shear for multi-story frames.

Key concepts this page covers

flush vs. extended end plate configurations
bolt prying action (thick and thin plate models)
column flange bending and stiffener requirements
yield line patterns in end plates

Inputs and outputs

Typical inputs: beam section, column section, end plate width and thickness, bolt diameter and grade, bolt layout (gage, pitch, number of rows), steel grades for plate and members, and factored moment and shear demands.

Typical outputs: bolt tension including prying, end plate bending capacity, column flange bending capacity, stiffener requirements (continuity plates, doubler plates), and overall connection moment capacity.

Computation approach

The calculator follows the AISC Design Guide 4 procedure. For extended end plates, the bolt force including prying is computed using the Kennedy method or the simplified AISC approach. The end plate thickness is checked against yield line mechanisms. Column-side checks include flange bending (using the equivalent T-stub model), web yielding, web crippling, and web compression buckling. If any column-side check fails, the required stiffener size is computed.

Frequently Asked Questions

What is prying action in bolted end plate connections? Prying action occurs when the end plate or column flange flexes under the applied tension, causing the contact point near the bolt line to act as a fulcrum. This increases the bolt tension beyond the applied tension by an additional prying force Q. The magnitude of Q depends on the plate thickness, bolt gage, and the distance from the bolt to the beam flange. Thick plates have minimal prying; thin plates can increase bolt tension by 20-40%.

What is the difference between flush and extended end plates? A flush end plate does not extend beyond the beam flanges; bolts are placed between the flanges. An extended end plate extends beyond one or both beam flanges, with bolt rows above and/or below the flanges. Extended plates have higher moment capacity because the outer bolt rows have a longer lever arm. The 4-bolt extended unstiffened (4E) and 8-bolt extended stiffened (8ES) are the most common configurations.

When are column stiffeners required? Column stiffeners (continuity plates) are required when the column flange is too thin to resist the concentrated force from the beam flange without excessive local bending, or when the column web cannot resist the compression or tension delivered by the beam flanges. The need for stiffeners depends on the column flange thickness, web thickness, column depth, and the magnitude of the beam flange forces. Stiffeners add fabrication cost, so selecting a heavier column to avoid stiffeners is often more economical.

Disclaimer (educational use only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice, a design service, or a substitute for an independent review by a qualified structural engineer. Any calculations, outputs, examples, and workflows discussed here are simplified descriptions intended to support understanding and preliminary estimation.

All real-world structural design depends on project-specific factors (loads, combinations, stability, detailing, fabrication, erection, tolerances, site conditions, and the governing standard and project specification). You are responsible for verifying inputs, validating results with an independent method, checking constructability and code compliance, and obtaining professional sign-off where required.

The site operator provides the content "as is" and "as available" without warranties of any kind. To the maximum extent permitted by law, the operator disclaims liability for any loss or damage arising from the use of, or reliance on, this page or any linked tools.