Crane Runway Beam — Industrial Beam Design

Crane runway beam design for wheel loads. Biaxial bending, lateral-torsional buckling, and fatigue category checks per AISC 360 and CMAA 70. Educational use only.

This page documents the scope, inputs, outputs, and computational approach of the Crane Runway Beam 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

Checking biaxial bending of crane runway beams under vertical wheel loads and lateral crane forces.
Evaluating lateral-torsional buckling for the top flange loaded by moving crane wheels.
Preliminary fatigue screening for crane duty cycle categories per AISC 360 Appendix 3 and CMAA 70.

What this tool is not for

It does not design the crane rail, rail clips, or crane girder connections.
It does not handle crane runway columns, bracing, or the building frame response to crane loads.
It does not perform a full fatigue assessment with stress range counting and cumulative damage analysis.

Key concepts this page covers

moving wheel load placement for maximum moment and shear
biaxial bending interaction (H1-1 interaction equation)
lateral force from crane trolley and skewing
fatigue categories and stress range limits

Inputs and outputs

Typical inputs: runway beam span, section size, crane capacity, wheel base, number of wheels, maximum wheel load, lateral load (percent of lifted load), and crane duty class.

Typical outputs: maximum bending moment (strong and weak axis), combined stress check (H1-1 interaction), deflection (vertical and lateral), and fatigue category check with allowable stress range.

Computation approach

The calculator positions the crane wheel loads on the span to maximize the bending moment using the influence line approach (for two or four wheels, the critical position is when the midpoint between the resultant and the nearest wheel is at the beam midspan). Lateral forces are applied as a percentage of the vertical load per ASCE 7 or CMAA. Biaxial bending is checked using the AISC H1-1 interaction equation. Fatigue is screened by comparing the live-load stress range to the allowable range for the applicable fatigue category.

Frequently Asked Questions

How are crane wheel loads positioned for maximum moment? For a single crane with two wheels per rail, the maximum moment occurs when the beam centerline is midway between the nearest wheel and the resultant of both wheel loads. This is a specific case of the general moving-load theorem. For four-wheel cranes, all possible wheel positions must be checked. The tool automates this positioning to find the critical arrangement.

What lateral forces act on a crane runway beam? Crane lateral forces arise from trolley acceleration/deceleration (typically 20% of the lifted load plus trolley weight, applied at the top of the rail), crane skewing forces (from the crane bridge not tracking straight on the rails), and impact. These lateral forces cause weak-axis bending in the runway beam. A separate channel or plate is often welded to the top flange to resist lateral bending, creating a compound section.

Why is fatigue important for crane runway beams? Crane runway beams experience repeated load cycles every time the crane traverses the span. Over a 25-year service life, a moderate-duty crane may impose 500,000 to 2,000,000 load cycles. AISC 360 Appendix 3 requires fatigue checks when the number of cycles exceeds 20,000, and the allowable stress range decreases with increasing cycle count and worse fatigue category (determined by the connection detail). Fatigue often controls the design of runway beams for medium and heavy-duty cranes.

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.