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Technical GuideWheel Loads and Building Structural Design
What is crane wheel load, how does it transfer to the building, what to check when adding a crane to an existing structure, and when a freestanding runway structure is needed.
What wheel load is
A crane's own weight and the load it lifts pass through its wheels onto the runway. The force each wheel presses onto the rail is called wheel load, and it varies with the crane's position: as the trolley moves toward one end, the wheel load on that side increases.
The calculation uses the worst case: maximum load, the trolley at the far end, and dynamic effects, all considered together.
| What to check | Why |
|---|---|
| Column section and capacity | Can it carry the vertical and horizontal crane loads |
| Bracket connection | The weld/bolt detail of the bracket carrying the runway |
| Foundation and ground | Settlement risk under increased load |
| Existing runway | Is the profile adequate, is its geometry within tolerance |
| Roof structure | Truss and purlin capacity if an underslung crane is being considered |
| Lateral stability | How the structure behaves under braking and skewing forces |
These checks are carried out by whoever handles the building's structural design; the crane manufacturer supplies the loads.
Not just vertical
A point often missed on the building side is that a crane doesn't only put vertical load on the structure. Accelerating and braking create horizontal forces, and a tendency to skew puts a lateral force on the runway.
These horizontal components matter most on runways carried by brackets and on semi-gantry installations. A check that only considers the vertical load is incomplete.
Adding a crane to an existing building
Three ways to solve it
A lighter crane: moving to a single girder, reducing the span, or matching capacity to the actual need noticeably lowers wheel loads. In most projects this is the most economical route.
Strengthening: reinforcing the column, bracket or foundation. Costly and disruptive to production, but necessary if the building simply won't work otherwise.
A freestanding runway structure: the runway sits on its own legs rather than the building. The building carries none of the load; if the ground is suitable, it's a clean solution. A gantry crane is another form of the same logic.
Technical terms
| Term | What it means |
|---|---|
| Wheel load | The force one wheel transfers to the rail and the structure. |
| Horizontal force | Lateral loads arising from acceleration, braking and skewing. |
| Bracket | A beam projecting from a column that carries the runway. |
| Freestanding runway structure | A steel structure carrying the runway independently of the building. |
| Dynamic effect | The increase over the static load caused by motion and sudden loading. |
Frequently asked questions
Who provides the wheel loads?
The crane manufacturer, after engineering the crane, documents the worst-case wheel loads and horizontal components. These values are what the building side works from.
My building is old with no drawings — what do I do?
The existing structure needs a survey and a condition assessment. Assumptions made without a structural record are risky; in most cases a freestanding runway structure ends up the safer route.
If I choose single girder instead of double, how much do the loads drop?
Noticeably, because the crane's own weight is lower. But lifting height and available equipment options narrow too — the decision has to be made together.