StruSheets
Crane Runway Loads: Choosing Impact Inputs
Understand the three impact fields and how the MBMA runway-beam load cases apply to one, two, or three cranes on the same runway.
What Each Field Means
| Input Field | What The Percentage Represents |
|---|---|
| Vertical Impact | An increase on the maximum static wheel load to account for vertical dynamic effects. Enter the static load in Maximum Static Wheel Load and the increase separately. |
| Horizontal Impact (Lateral) | The basis for the crane’s transverse force across the runway. In the runway worksheet, the percentage is applied to the rated lifted load plus trolley and hoist weight before distribution to the wheels. |
| Longitudinal Impact | The basis for the force along the runway, such as traction or braking. In the runway worksheet, this percentage is applied to the static wheel load. |
For more than one crane, enter the geometry and loads for each crane separately and number the cranes in their physical order along the runway. Blank impact percentages in the additional columns inherit Crane 1. Edit a percentage if that crane has different project criteria. Values suggested by the worksheet are starting points for review.
MBMA Runway Beam Load Cases
The factors below apply to the crane loads in a design case.
| Case | Vertical Wheel Loads | Lateral Forces |
|---|---|---|
| Single Crane · Section 2.6.1 | Maximum wheel loads plus the full vertical impact increment (100%). | At the same time, use the full lateral force (100%) and check either direction. |
| Governing Single Crane · Section 2.6.2 | For a runway with multiple cranes, check the single crane producing the most adverse effect using Section 2.6.1. | Use the single-crane lateral check. |
| Most Severe Adjacent Pair · Section 2.6.2 | Use the maximum static wheel loads of both cranes together, with 0% vertical impact on either crane. | Compare 50% of each crane’s lateral force acting together with 100% of either crane’s lateral force acting alone. Both cranes’ static wheel loads remain in each comparison. Use the more severe effect. |
For a continuous runway beam, compare the pair’s lateral forces acting in the same direction and in opposite directions.
Three Cranes On One Runway
For cranes arranged 1 → 2 → 3, compare the single-crane cases for Cranes 1, 2, and 3 and the two adjacent-pair cases, 1 + 2 and 2 + 3. Section 2.6.2 does not specify a simultaneous three-crane case. The three input columns let you enter data for all three cranes.
How The Factors Relate To The Inputs
For example, if the project specifies 10% vertical impact and a 100 kN maximum static wheel load, the impact increment is 10 kN. Taking 100% of that increment gives 110 kN for the single-crane case. The same wheel contributes 100 kN in an adjacent-pair case without impact. If a crane’s nominal lateral force is 20 kN, half of that force is 10 kN.
The example values are illustrative. The MBMA percentages describe how much of an already established load to use in a design case. Choose the field values using the project’s governing code, crane classification, manufacturer data, and design scope. Confirm the vertical impact, lateral-force magnitude, and longitudinal-force value with the project’s structural engineer and crane supplier.
Runway Beam Design evaluates the selected crane train. Use this guidance and the worksheet’s report to identify any cases that need a separate check for your project.
See the MBMA Metal Building Systems Manual, Section II, Sections 2.6.1–2.6.2, “Runway Beams and Suspension Systems.”
This article provides general educational information. Project-specific structural design, calculations and drawings should be reviewed by appropriately qualified engineering professionals and checked against applicable project requirements and standards. StruTools does not replace engineering judgement or professional design review.