Козловой кран с ферменной конструкцией против козлового крана коробчатой формы: инженерное сравнение, анализ затрат и руководство по выбору для использования на открытом воздухе.

A балочный козловой кран outperforms a box-girder gantry crane on high-wind coastal or mountain sites, on spans beyond 25–30 meters, in temporary precast concrete yards, and wherever soil bearing capacity is low. The open lattice cuts structural deadweight by 20%–35%, removes 60%+ of the windward surface area, and can lower total project cost (crane plus civil runway foundation) by 15%–30%. Those savings come from physics, not from thinner steel: bending stress is converted into axial force in the truss members, and crosswind passes through the structure instead of loading it.

Starting with the key factors in deciding on the purchase of outdoor lifting equipment, this guide compares these two structural types, including wind load characteristics, wheel load and foundation costs, deflection under long spans, duty classes, corrosion protection and maintenance, and equipment relocation. In addition, this guide identifies specific operating conditions for which truss gantry cranes are not suitable. Please continue reading:

Why Triangular Space Truss Design Changes Outdoor Lifting Economics

A truss girder is built from angle steel or structural tubing arranged in triangulated panels. Each member carries mainly tension or compression, which is the most efficient way to use steel. A box girder resists the same load through plate bending, so it needs thick webs and flanges, internal diaphragms, and long submerged-arc welds. The buyer feels this difference well beyond the FOB crane price: in wind loads, in the concrete under the rails, and in the cost of moving the crane to the next site.

1. Windward Area Reduction & Wind Load Mechanics

A solid box girder presents a continuous vertical plate to crosswind. An open lattice lets air pass through the grid, so the windward area falls to roughly 30%–40% of an equivalent box girder. Wind force scales with exposed area, so the force on the structure drops by a similar proportion.

• Lower long-travel power: less headwind drag on the structure means the long-travel drives can be sized smaller, and the crane holds position more easily on the rails.
• Safer working window: a truss crane stays controllable in Beaufort Scale 6–7 winds, where a box crane often reaches its anemometer cut-off earlier.
• Smaller overturning moment in storms: with the crane out of service and locked down, the wind-induced overturning moment on legs, rail clamps and anchors is much lower, so those restraints can be lighter.

2. Deadweight, Wheel Load & Civil Runway Foundation Savings

Most buyers tend to overlook the track foundation when focusing on crane prices. The construction cost of a concrete track foundation typically accounts for 15%–25% of the total project investment, and its scale depends on the crane’s “maximum wheel load” rather than solely on its rated lifting capacity.

Since truss structural members primarily bear axial tensile and compressive forces, the dead weight of a truss crane can be reduced by 20%–35% compared to a box-girder structure with the same lifting capacity and span. This reduction in dead weight lowers the maximum wheel load at the track support points, thereby allowing for narrower or shallower foundation beams. On soft ground or leased sites, this design can even eliminate the need for deep pile foundations entirely and make temporary track solutions using ballast counterweights or sleeper tracks a viable option.

The following examples are for reference only (informal estimates): Assuming a box-girder gantry crane costs 100 units and its track foundation costs 30 units, the total project investment would be 130 units; whereas a truss gantry crane costs 92 units and its track foundation costs 18 units, resulting in a total project investment of 110 units—a reduction of approximately 15% in total cost. Actual figures may vary depending on span, geological conditions, local concrete prices, and steel market conditions; therefore, please consider this a comparative analysis rather than an exact pricing reference.

3. Long-Span Deflection Control (25m to 40m+ Spans)

Self-weight deflection grows quickly with span. Beyond about 30 meters, a solid box girder needs thicker plate and deeper sections to stay within deflection limits, which adds the very weight that causes the sag. A triangular or four-chord space truss gets its depth from the geometry rather than from plate thickness, so stiffness rises faster than mass.

The result is a crane that can reach 40m and beyond without a steel-plate penalty, while keeping wheel loads manageable. Camber can also be set in the truss during fabrication and trimmed at bolted joints on site.

Truss vs. Box-Girder Gantry Crane: Head-to-Head Engineering Comparison

The table compares both structures across eight engineering and commercial dimensions. The figures are typical design ranges and should be confirmed against your site data.

Измерение	Truss (Lattice) Gantry Crane	Box-Girder Gantry Crane
Primary material & welding	Rolled section steel (angle, I-beam) or structural tubing; node and chord welding, with bolted segment joints	Q235B / Q355B steel plate; long submerged-arc welded web and flange seams
Wind resistance	Windward area about 30%–40% of a box girder; well suited to coastal and mountain sites	Full solid plate area exposed; higher drag and overturning moment
Deadweight & Max Wheel Load	20%–35% lighter; lower wheel load per rail support	Heavier structure; higher wheel load
Civil runway foundation cost	Smaller footing; piling often avoidable; temporary track feasible	Heavier beams or piles on weak soil; usually a permanent runway
Optimal span & capacity	3–100T, 7.5–40m+; strongest advantage beyond 25–30m	Best on short to medium spans and heavy continuous-duty capacities
Recommended duty class	ISO A3–A5 / FEM M3–M5	ISO A5–A8 / FEM M5–M8
Repainting & anti-corrosion	More surface area and multi-angle corners; needs careful coating and periodic touch-up	Flat plates are easy to shot-blast and coat; lower maintenance effort
Relocation & segmental disassembly	Bolted segments; compact, easy to ship and re-erect between project sites	Large welded sections; harder to split and ship; less suited to frequent moves

Примечание: Truss structures offer greater advantages when wind loads, foundation conditions, span, or mobility are key factors affecting cost; however, this comes at the cost of fatigue life issues and the maintenance of anti-corrosion coatings. If service conditions, corrosive environments, or clearance height are central considerations in decision-making, box girder structures are more suitable. Please review the row corresponding to your greatest risk first, then verify the other information. If wind loads and foundation conditions are the primary constraints, truss structures should be prioritized. If service class and corrosive environments are the primary constraints, box girder structures should be prioritized.

Structural Configurations: Full Truss vs. Hybrid “Box-Girder + Truss Legs”

Standard catalog models cover most yards, but site conditions often call for a modified structure. The MH single-girder and MG double-girder truss gantry cranes are the base platforms. From there, the main girder and the legs can each be built as truss or box, depending on what the site demands.

1. Full Truss Single-Girder (MH Type, 3–20 Ton)

Best for light-to-medium open stockyards, pipe pile plants, and stone and timber yards. The hoist, either a CD1/MD1 unit or a European-style wire rope hoist, runs along the lower I-beam chord. The design is light, quick to erect, and economical to ship.

2. Full Truss Double-Girder (MG Type, 40–100 Ton)

Built for heavy precast concrete beam yards, highway and railway bridge construction, and wide-span outdoor fabrication. Two truss girders carry a heavy-duty winch trolley, and optional cantilevers let trucks load and unload outside the rails.

3. Hybrid Configurations: “Box Girder + Truss Legs” & “Truss Girder + Box Legs”

Some sites need both properties at once. A client may want high trolley rigidity and low maintenance on the main beam, favoring a box girder, while working in a high-wind coastal zone that calls for low wind drag and lighter legs, favoring a truss. VOITTO CRANE engineers a hybrid for this case: a box main girder on truss support legs.

• Box girder + truss legs: stiff, easy-to-coat runway for the trolley, with lower leg weight and wind drag where the structure is tallest.
• Truss girder + box legs: long-span weight savings in the girder, with solid legs where impact, corrosion, or vehicle strikes are a concern.

Engineering Red Lines: When You Should NOT Choose a Truss Gantry Crane

A truss crane is not the right answer everywhere. In three situations, we advise buyers to move to a heavy-duty box-girder crane.

• High-frequency, continuous full-load operating conditions (ISO A6–A8 / FEM M6–M8). Welded joints in truss structures are subjected to high-cycle alternating stresses, which often lead to fatigue cracks. Box-girder structures should be used in steel mills, scrap metal processing yards (where electromagnetic lifters are used), and container terminals operating around the clock (24/7). Stress is transmitted through continuous steel plates, reducing stress concentrations.
• Environments subject to severe corrosion (e.g., chemical plants, acid pickling shops, or salt spray environments). At the intersections of multiple members in truss structures, coating blind spots can form, leading to thinner coatings and moisture accumulation in these areas. In contrast, shot-blasted box girders have a smooth surface, allowing for uniform coating coverage and making them easier to inspect and recoat.
• Applications with limited vertical clearance (such as indoor or semi-outdoor work areas). For the same lifting capacity and span, the vertical cross-sectional height required for a truss girder is typically greater than that of a box girder. If the building structure limits hook height, the use of low-profile box girders is more appropriate.

5-Point Pre-Inquiry Engineering Checklist for Outdoor Buyers

Before the procurement team requests a quote or structural drawings, please have these five items ready. They will enable engineers to determine whether to use a truss, box, or hybrid structure during the initial evaluation, rather than having to wait until the third evaluation to make a decision.

• Local wind speed distribution: This includes the maximum in-service wind speed (in m/s or km/h) and wind loads (wind pressure) during non-operational periods. These parameters determine the configuration of the rail clamps, anchoring devices, and anemometer interlock devices.
• Track span and effective cantilever length: This refers to the track center-to-center distance (7.5 meters to 40 meters); if the crane outriggers are located outside the track, the cantilever lengths on both sides must also be considered.
• Foundation Bearing Capacity and Foundation Type: Foundation types may include permanent concrete beams or temporary ballast tracks or sleeper tracks designed for civil infrastructure projects lasting 2 to 5 years.
• Lifting Capacity, Lifting Height, and Duty Cycle: Includes rated load (3 tons to 100 tons), hook travel (6 meters to 24 meters), and daily operating hours.
• Relocation and Transportation Restrictions: If transportation through 40-foot high-cube (HQ) containers is required or if frequent relocation between different sites is necessary, the structural truss should adopt a segmented, bolted design. After each reinstallation, a thorough inspection must be conducted in accordance with the gantry crane comprehensive checklist, strictly examining wind-resistant locking devices, anchoring devices, structural bolts, and welds.

Заключение

No single structural type is absolutely superior to another in all situations. When wind loads, span, foundation conditions, or the need for equipment relocation become key factors affecting cost, truss gantry cranes are the ideal choice. Their design reduces the wind-exposed area to 30%–40% of that of a box-girder structure, reduces dead weight by 20%–35%, and significantly lowers wheel load. For high-duty-class applications, corrosive environments, and situations with limited headroom, box-girder double-girder gantry cranes are the optimal solution.

Truss Gantry Crane Manufacturer and Supplier

As a truss gantry crane manufacturer and supplier, VOITTO CRANE engineers and fabricates heavy-duty MH single-girder, MG double-girder, and hybrid lattice gantry cranes tailored to your exact wind zone, soil bearing capacity, and span requirements.

Explore our full line of custom-engineered truss gantry crane solutions or send us your required tonnage, span, lifting height, and local wind speed today to receive a free structural layout drawing and factory-direct quotation within 24 hours.

ЧАСТО ЗАДАВАЕМЫЕ ВОПРОСЫ

What wind speeds can an outdoor truss gantry crane withstand during operation and when locked in place during a storm, respectively?

In service, most outdoor gantry cranes are set to stop working at about Beaufort 6–7 (roughly 14–17 m/s), when the anemometer triggers an alarm and cut-off. Non-working storm resistance is a design value calculated for each site from local wind data, and it is secured with rail clamps, anchoring shoes, or chains. Please send your site’s maximum recorded wind speed so the structure and restraints are sized to it.

Can a 30m–40m span truss gantry crane be shipped inside standard 40ft High Cube containers?

Yes, when the girder is designed as bolted segments. A 40ft High Cube container has an internal length of about 12 meters, so segments are usually kept under that length, and the legs, trolley, and hoist are packed alongside. Very heavy or oversized parts may need flat-rack or open-top containers. Specify the shipping plan at inquiry so the segment lengths are built into the design.

How do you prevent rust at the welded joints of a truss gantry crane in humid outdoor environments?

Protection starts before painting: shot-blasting to a clean standard, followed by a zinc-rich primer, an epoxy intermediate coat, and a polyurethane topcoat. Stripe-coating the edges and nodes adds film thickness where lattice corners are hardest to cover. Tube ends should be sealed, drain paths kept open, and bolted joints galvanized, with periodic touch-up as part of routine inspection.

Is a hybrid “box girder + truss legs” crane more expensive than a full truss gantry crane?

Usually yes, because the box girder adds plate fabrication and long welded seams. It normally costs less than a full box crane of the same span, since the legs are lighter and the wind and foundation loads are lower. The extra cost is often recovered through lower trolley-girder maintenance and better rigidity, so compare lifetime cost rather than purchase price alone.