Crane Beam & Monorail Calculator

Crane Runway Engineering Guide

Deflection Limits: L/450 vs L/600

Deflection is often the governing factor in crane runway design. The CMAA (Crane Manufacturers Association of America) and AISC Design Guide 7 recommend specific limits based on the duty cycle of the crane.

L/450: Standard limit for light to medium duty cranes (Classes A, B, C). This prevents noticeable "sag" as the load moves.
L/600: Stricter limit for heavy duty (Class D) or mill duty cranes. This minimizes wear on the mechanical trolley components.
L/800 or L/1000: Used for severe service or when tight tolerances are required for automated systems.

S-Shapes vs. W-Shapes

While Wide Flange (W) beams are more efficient for bending, American Standard (S) beams are frequently used for monorails and underhung cranes.

Why? The S-shape has a tapered flange (approx 16.7% slope) which matches the tapered tread of many standard trolley wheels. Running a tapered wheel on a flat W-beam flange effectively creates a point load on the edge of the wheel, causing rapid wear. If using W-shapes for underhung cranes, ensure the trolley wheels are "flat tread" or compatible with wide flanges.

Impact Factors (CMAA 70)

Vertical loads must be increased to account for the sudden movement of lifting. This tool applies a multiplier to the Lifted Load + Hoist Weight (but not the Bridge Weight).

Pendant/Radio Control (10-15%): Smoother operation allows for a lower impact factor.
Cab Operated (25%): Higher speeds and aggressive acceleration typically require a 25% increase in vertical load design.

How to use the two modes

Find Lightest Beam: Enter span, loads, and deflection limit. The tool searches common S and W shapes and reports a candidate that meets the checks.
Check Specific Size: Enter a known designation to verify capacity and deflection for as-built or preferred shapes.
Always reconcile results with the project engineer of record, crane manufacturer criteria, and applicable AISC / CMAA provisions.

FAQ

Is this a stamped design?

No. It is a preliminary sizing aid for detailers and estimators. Final runway design must be sealed by a licensed engineer for the jurisdiction and crane class.

Does the tool include lateral loads and fatigue?

Vertical bending and deflection govern many light-duty checks here. Lateral thrusts, fatigue categories, and support/column interaction need separate review for heavier service.

When should I pick L/600 instead of L/450?

Use the stricter limit for heavier duty cycles, cab-operated cranes, or when the crane OEM specifies reduced deflection to protect trolley and bridge components.

Why might an S-shape win over a lighter W-shape?

Monorail trolley wheel geometry often favors the tapered S flange. A lighter W may pass flexure yet be a poor wheel runway without flat-tread wheels or a patented track system.

Load Data

Geometry

Criteria

W21x44