AISC Design Guide 16: Flush and Extended Multiple-Row Moment End-Plate Connections

How to Apply AISC Design Guide 16: Flush and Extended Multiple-Row Moment End-Plate Connections

Mastering the design of flush and extended multiple-row moment end-plate connections is a critical skill for structural engineers. AISC Design Guide 16 provides the foundational knowledge and systematic procedures to ensure these complex connections perform reliably under significant bending moments. By understanding and correctly applying the principles outlined in this guide, you can confidently design robust moment-resisting frames and seismic force-resisting systems, enhancing your project outcomes and professional credibility.

Before You Begin

Prerequisites:

• • Knowledge: A solid understanding of structural steel design principles, including Load and Resistance Factor Design (LRFD) and Allowable Strength Design (ASD) methodologies. Familiarity with the AISC Steel Construction Manual, particularly chapters concerning bolted connections and limit states, is essential.
• • Tools/Resources: Access to AISC Design Guide 16, the AISC Steel Construction Manual, engineering design software (optional, for verification), and relevant material property data.
• • Time Required: Approximately 2-4 hours, depending on the complexity of the connection and familiarity with the design guide's procedures.

Step-by-Step Implementation

Step 1: Define Connection Geometry and Applied Loads

Begin by meticulously gathering all geometric parameters of the connection, including beam and column dimensions, end-plate dimensions, bolt spacing, and distances from bolt lines to the column flange. Concurrently, determine the governing factored moment ($M_u$) or service moment that the connection must resist, as dictated by structural analysis. Accurately defining these inputs is paramount, as any discrepancies will propagate through subsequent calculations.

Step 2: Select an Initial Design Procedure and Trial Parameters

AISC Design Guide 16 presents two primary design procedures. Procedure 1 typically results in a thicker end-plate and smaller diameter bolts, while Procedure 2 often yields a thinner plate and larger diameter bolts. Select one procedure based on preliminary considerations or project requirements. Choose a trial bolt diameter ($d_b$) and end-plate material, referencing the specified material grades (e.g., A572 Gr 50).

Step 3: Determine Required End-Plate Thickness

Using the selected design procedure and trial parameters, calculate the minimum required end-plate thickness ($t_{p,reqd}$). This calculation involves evaluating various limit states, including the yielding of the end-plate, bolt shear, and bolt rupture, while accounting for prying action. The guide provides specific equations for these checks, often referencing "summary tables" for guidance. Ensure the calculated thickness is adequate for all identified limit states.

Step 4: Calculate Prying Forces and Bolt Design Strength

For connections with multiple bolt rows, especially flush and interior bolts of extended end-plates, it is crucial to calculate the maximum prying force. This force arises due to the deformation of the end-plate and can significantly increase the load on individual bolts. Subsequently, determine the connection's design strength for the limit state of bolt rupture, incorporating the effects of prying action. This involves using equations specific to flush or extended end-plate configurations.

Step 5: Evaluate End-Plate Strength and Bolt Rupture Capacity

Verify that the selected end-plate thickness is sufficient to prevent combined flexural and shear yielding. If the calculated values indicate a negative radical in specific equations, the end-plate is inadequate. Then, calculate the design strength of the bolts considering prying action. Compare this calculated strength against the applied moment. For extended end-plate connections, pay close attention to the distinct prying action calculations for interior versus exterior bolt rows.

Step 6: Iterate and Verify Design Strength

If the calculated connection design strength is less than the required factored moment ($M_u$), you must