The two machine classes are mechanically similar — both use a horizontal bridge girder carrying a hoist trolley — but differ in load path: a gantry crane carries the bridge on A-frame or box leg assemblies running on ground-laid rail, while an overhead bridge crane hangs the bridge from elevated runway rails fixed to the building structure [S1][S2].
Standard factory spans for single-girder bridge units cover 7.5–31.5 m at 1–32 t, while double-girder packages reach into the 1–500 t range with lifting heights of 6–30 m [S5]; modular double-girder gantry systems in the same supplier family publish 100 t as a routine upper figure, with custom builds scaling further [S3].
Load path and civil-work boundary
An overhead bridge crane transfers wheel loads into the building's columns via runway beams, so the steel building must be designed for those reactions; typical bridge spans sit between 7.5 m and 31.5 m on single-girder builds [S5], and creep upward on double-girder heavy-duty units. A gantry crane instead places the rail on a dedicated grade beam or strip foundation at floor level, so the building is not in the load path [S2].
That single decision drives the civil scope: a greenfield shed with no crane-rated columns almost always goes gantry, while an existing portal-frame building with adequate eaves height is cheaper to retrofit with a bridge crane than to pour a new rail foundation [S4][S6]. For higher lifts, the bridge crane's hoist rope can exploit the full building clear height without a leg eating headroom, a real advantage inside warehouses with limited truss depth.
Capacity, span and configuration envelopes
Single-girder bridge cranes cover the light end: 1–30 t is the routine band on European-style single-girder packages, with 1–32 t and spans of 7.5–31.5 m common on Chinese OEM datasheets [S1][S5]. Double-girder bridge units open the heavy end, with suppliers publishing 1–500 t for general industry and dedicated heavy-duty SKUs. Gantry cranes follow the same envelope but start lower: 1–10 t wire-rope hoist on light single-leg gantries, scaling through A-frame double-girder gantries to 100 t and beyond on modular kits [S3][S5].
When spans exceed about 30 m, a gantry leg grows tall and a bridge crane tends to win on steel tonnage, but the gantry can still be specified for outdoor yards where the building simply does not exist. Lifting heights of 3–22.5 m on light gantries and 6–30 m on bridge cranes set the upper practical reach for standard catalogues, with engineered specials pushing all of these upward.
Decision matrix: bridge vs gantry
Four criteria separate the two cleanly, and most 2026 RFQs come down to a pairwise score on this matrix: [S1]
1. Building integration — bridge crane requires runway beams on the column line; gantry does not. Score bridge if a crane-rated steel building exists or is in the BOM; score gantry otherwise [S1][S4].
2. Outdoor / yard use — gantry handles rain, sun and wind on a ground rail; bridge crane is a strictly indoor machine protected by the building envelope [S2][S3].
3. Capacity headroom — both reach 100 t+; gantries in the 1–100 t modular band are the most competitive on lead time, while double-girder bridge units dominate above 200 t where workshop fit-out is already in place [S3].
4. Headroom efficiency — a bridge crane gives the full building clear height to the hook, while a gantry loses roughly one leg height plus the bridge depth; in low-truss sheds this can be 1–2 m of usable lift lost [S5][S6].
Where each type fits — and where it does not
Bridge cranes suit repetitive indoor lifts in machine shops, steel fabrication bays, warehousing and assembly lines where the runway can be hung from existing columns, with double-girder units reserved for 32 t and up or for duty cycles needing higher hoist class [S5]. Gantry cranes suit container yards, precast concrete yards, scrap yards, shipyard aprons and any outdoor storage application where a building is either absent or too expensive to extend; modular A-frame gantries also serve factories that need to be reconfigured, since the rail can be relocated without disturbing the superstructure [S3][S4].
Neither type is a fit for very low-volume lifts where a mobile crane is the cheaper tool of choice, nor for high-reach building work where a crawler crane or tower crane is the established machine. The cutover is roughly 50–100 lifts per shift, below which mobile and forklift-style handling competes on total cost.
Operational constraints and failure modes
Bridge cranes depend on the building's runway alignment, and any column settlement shows up as trolley skew, wheel flange wear and end-carriage hunting; the cure is a civil survey before commissioning and a re-alignment budget every 5–10 years. Gantry cranes side-step the building problem but inherit the rail foundation, so differential settlement between leg rails is the dominant field complaint on long-span outdoor units [S2][S6].
Wind is an outdoor-only problem: open-yard gantries in coastal or cyclone-rated regions need rail clamps, storm pins or pin-up procedures above a documented wind threshold; bridge cranes inside an enclosed building do not. Conversely, dust, salt and temperature swings attack gantry leg connections and ground-rail fastenings far harder than indoor runway beams, so paint specification and rail-clip material deserve a real line item, not a default. Buyers who skip this end up with the same crane scale retrofit bill two years in, because the weighing system drifts when the structure flexes in wind.
Standards, sourcing and 2026 supply signal
Honour-based licensing and ISO 9001:2000 quality-system compliance appear on multiple Chinese OEM factory disclosures, with audited manufacture of bridge, gantry and KBK crane families under one roof [S6]. Other suppliers in the 2026 catalogue publish explicit envelopes: 1–10 t wire-rope hoist gantries, 1–32 t single-girder bridges, and 1–500 t double-girder bridges as the routine catalogue band [S5]. For yard buyers the modular Australian kit advertises a 100 t double-girder gantry, with A-frame support and a "low carbon" power-saver drive variant listed as the headline SKU [S3].
For buyers comparing gantries with the broader lifting fleet, the same spec-vs-application discipline used for truck-mounted vs tower cranes in 2026 applies: capacity, span, lift height, duty cycle and civil interface, in that order. Indoor heavy-duty shops with existing runway beams should default to the double-girder bridge; outdoor yards, port aprons and relocatable layouts should default to the modular gantry, and revisit the choice only when capacity or headroom breaks the envelope.
Two trackable signals for the back half of 2026: first, watch whether more Chinese OEM datasheets push their double-girder bridge envelope past 500 t as a standard SKU rather than a custom-engineered special; second, watch whether modular gantry kits in the 50–100 t band pick up a wider rail-clamp or storm-pin option in the catalogue, signalling that outdoor duty is becoming a default rather than a special.