What is a top running overhead crane?
A top running overhead crane is an electric overhead travelling (EOT) bridge crane whose end-trucks ride on top of rails mounted to the top flange of the runway beams. The bridge spans the bay and travels the length of the building on this elevated runway, while the trolley and hoist traverse across the bridge. It is the most common configuration for general industrial lifting because the load path runs straight down through the rails into the runway and the supporting columns — the structurally efficient way to carry heavier loads over longer spans.
The contrast is the underslung (or under-running) crane, where the end-trucks hang from and run along the lower flange of the runway beams. Top-running puts the wheels on top of the rail; underslung hangs the bridge beneath it. That single difference drives most of the trade-offs below.
How a top running overhead crane is configured
A top running overhead crane can be built as either a single-girder or a double-girder bridge:
- Single-girder, top-running — one bridge beam on two end-trucks running on top of the runway rails. Economical for light to medium capacities and moderate spans.
- Double-girder, top-running — two bridge beams with the crab/trolley running on rails on top of them. Used for higher capacities, longer spans, greater hook height and harder duty classes.
In both cases the runway is a critical part of the design. Because the wheel loads bear down on top of the rail, the runway beams and the building columns must be sized for the full vertical and lateral crane loads. On a top running overhead crane the runway is normally a dedicated structural runway beam with a crane rail, rather than the building's own roof structure.
Top-running vs underslung — side-by-side
| Wheel arrangement | Top-running: end-trucks run on top of rails fixed to the runway beams. Underslung: end-trucks hang from and run on the lower flange of the runway beams. |
| Typical capacity | Top-running: 1 t to 100 t+ with custom engineering. Underslung: typically up to ~10 t, most common under 5 t. |
| Span range | Top-running: economical from ~5 m to 35 m+. Underslung: best suited to shorter spans, typically under ~15 m. |
| Duty class | Top-running: comfortable across A3–A8 with appropriate design. Underslung: typically lighter duty, A2–A5. |
| Hook height / headroom | Top-running: bridge sits above runway, consuming some headroom near the top of the bay. Underslung: bridge hangs below the runway, but can run very close to the columns, improving side approach. |
| Runway support | Top-running: needs a dedicated structural runway and columns sized for crane loads. Underslung: can sometimes be supported from suitable building roof steel, subject to engineering check. |
| End approach | Top-running: larger end approach — hook can't reach fully to the runway ends. Underslung: tighter end and side approach — useful where floor coverage to the walls matters. |
| Best for | Top-running: heavier loads, longer spans, harder duty, new or upgraded runways. Underslung: lighter loads, maximising floor coverage, lower-headroom retrofits. |
When a top running overhead crane is the right choice
- Capacity above ~10 tonnes — top-running is the structurally efficient way to carry heavier loads.
- Longer spans — beyond ~15 m, top-running handles deflection and wheel loads better than underslung.
- Harder duty cycles — A5 and above, where the crane runs frequently or near rated load.
- A dedicated runway is available or being built — new construction or a structural upgrade where columns and runway beams can be sized for crane loads.
- Maximum hook height isn't constrained at the very top of the bay — you have the headroom to put the bridge above the runway.
- Double-girder features are needed — auxiliary hoist, maintenance walkway, or greater under-hook height.
Limitations to weigh
- Headroom near the roof — the bridge sits above the runway, so it consumes some of the clearance at the top of the bay. In a low-headroom building, an underslung or low-headroom configuration may suit better.
- End approach — the hook cannot travel fully to the ends of the runway, leaving dead zones at each end of the bay.
- Runway cost — a dedicated structural runway and adequately sized columns add to the capital cost, particularly in an existing building not originally designed for a crane.
- Building loads — the columns and footings must carry the crane's vertical and lateral loads, which needs a structural check.
Design and compliance
In Australia, overhead bridge cranes — including top running overhead cranes — are designed to AS 1418 (the crane design code), with the structure assessed for the relevant duty class and load combinations. Once in service, inspection and maintenance follow AS 2550. Capacity is expressed as the Maximum Rated Capacity (MRC) — the load the crane is rated and marked to lift. The runway and supporting structure are part of the same engineering exercise: a top running overhead crane is only as good as the runway it travels on, so the runway beams, rails, columns and footings must all be verified for the crane loads.
Talk to an engineer
Sorian designs, manufactures and installs top running overhead cranes — single- and double-girder — engineered to AS 1418. Send through your span, MRC, duty cycle, headroom and whether you have an existing runway and we'll come back with a configuration recommendation.
Frequently asked questions
What is a top running overhead crane?
A top running overhead crane is an EOT bridge crane whose end-trucks ride on top of rails fixed to the runway beams. The load path runs straight down through the rails into the runway and columns, which makes it the structurally efficient choice for heavier loads, longer spans and harder duty cycles.
What is the difference between a top-running and an underslung overhead crane?
A top-running crane runs on top of rails on the runway beams; an underslung crane hangs from and runs along the lower flange of the runway beams. Top-running suits higher capacities, longer spans and harder duty, while underslung suits lighter loads, lower headroom and tighter floor coverage.
When should I choose a top running overhead crane?
Choose top-running for capacities above roughly 10 tonnes, longer spans (beyond about 15 m), duty class A5 and above, or where a dedicated runway is available or being built. It is also the configuration used when double-girder features such as an auxiliary hoist or maintenance walkway are required.
What standards apply to a top running overhead crane in Australia?
Top running overhead cranes are designed to AS 1418, with capacity stated as the Maximum Rated Capacity (MRC), and inspected and maintained in service to AS 2550. The runway beams, rails, columns and footings are part of the same engineering check, since the crane loads are carried straight into the supporting structure.