Wheel Load Distribution in EOT Cranes
How dynamic lifting forces translate into massive concentrated loads on your wheels, rails, and building columns.
Want to calculate Maximum Wheel Load?
Input your crane's span, hook approach, and dead weights to instantly compute the extreme load reactions at each wheel.
The Moving Load Problem
Unlike a bridge over a river where the main load is the weight of the pavement, an EOT crane is a dynamic system. The heaviest element (the loaded trolley) moves constantly across the span. Because of this, the load experienced by the supporting columns changes drastically depending on exactly where the trolley is parked.
If the trolley is parked all the way to the left side of the bridge, the left wheels will experience maximum compression, while the right wheels will experience their minimum load.
Why Civil Engineers Care
Crane manufacturers design the crane, but civil engineers design the building. The single most important piece of data a structural engineer needs from the crane supplier is the Maximum Wheel Load. Without this, they cannot properly size the concrete corbels, steel columns, or the gantry runway beams.
Hook Approach Limits Load Transfer
You might think that if you lift 10 tons on the left side of the crane, the left wheels take all 10 tons. This is not physically possible because of the Hook Approach.
The trolley is bulky. It cannot drive until the hook touches the factory wall; it is stopped by physical end stops or buffers. This distance from the center of the rail to the closest point the hook can reach is the Hook Approach. Because the load is never directly over the wheels, it is always distributed across the span based on the lever arm principle.
The Formula for Maximum Wheel Load
For a standard 4-wheel EOT crane, the maximum reaction force on one side of the bridge is calculated using simple statics (summing the moments about the opposite rail):
Reaction = (Bridge Weight / 2) + [(Trolley Weight + SWL) × (Span - Hook Approach)] / Span
Since this reaction force is shared by two wheels on the end carriage, you simply divide this number by two to get the Maximum Wheel Load per wheel.
Selecting the Wheel Size
Once the Maximum Wheel Load is calculated, the mechanical design engineer must select the correct forged steel wheel. The size of the wheel depends on two things:
- The Load: Heavier loads require larger diameter wheels to prevent crushing the rail.
- The Rail Profile: The wheel tread width must match the rail head width (e.g., a CR80 rail requires a wider wheel than a 50x50 square bar).
Automate the Calculation
Calculating wheel loads requires balancing multiple variables including impact factors, duty cycles, and hook approaches.
Instead of doing manual moment calculations, you can use our interactive calculator to instantly determine both the maximum and minimum wheel loads for any crane configuration.