What Is The Most Efficient Method To Account For The Effects Of Shear Lag On The Flexural Capacity Of A Wide-flange Steel Beam With A Non-prismatic Cross-section, Particularly When Subjected To A Combination Of Axial Loads And Lateral Loads From Wind Or Seismic Activity, In Accordance With The Latest AISC 360-16 Provisions?

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To efficiently account for the effects of shear lag on the flexural capacity of a non-prismatic wide-flange steel beam subjected to axial and lateral loads, follow these steps in accordance with AISC 360-16:

Step 1: Segment the Beam

Divide the beam into segments where each segment has a constant cross-section. This allows you to analyze each part separately, considering the varying geometry.

Step 2: Analyze Loads for Each Segment

For each segment, determine the maximum shear force (V) and bending moment (M) due to the applied loads, including axial forces.

Step 3: Determine Effective Flange Width

Using AISC 360-16 provisions, calculate the effective flange width (b_e) for each segment to account for shear lag. This may involve using formulas from sections like F4.5.3.2, which consider the distance between web reinforcements or fasteners and flange slenderness.

Step 4: Calculate Flexural Capacity

For each segment, compute the flexural capacity (Mn) using the effective flange width. This adjusts the capacity to reflect the reduced contribution of the flanges due to shear lag.

Step 5: Check Interaction with Axial Loads

If axial loads (P) are present, use the AISC interaction equations (H1.1) to ensure the combined effect of P and M does not exceed the member's capacity, considering the adjusted flexural capacity from shear lag.

Step 6: Identify Governing Segment

Evaluate each segment to find the one with the lowest capacity relative to demand. This critical segment will govern the design, ensuring overall structural integrity.

Conclusion

This method efficiently accounts for shear lag by segmenting the beam, calculating effective widths, adjusting capacities, and checking interactions, all in compliance with AISC 360-16.