Steel Bridges & Infrastructure — Long-Span Structures Over Water, Roads & Rail

Live loads rule bridge design. A road bridge carries traffic live loads of 0.6-1.8 kN/m² per lane (GB 50917-2014 standard vehicle, EN 1991-2 Load Model 1, or AASHTO HL-93), but the governing case is the notional 300-600 kN vehicle or the 25-40 tonne axle that produces concentrated effects. A rail bridge adds a 22.5 tonne axle at 1.5 m spacing (GB standard) or 25 tonne (UIC 71), multiplied by a dynamic amplification of 1.1-1.5 depending on speed. These loads sit on a deck whose own weight is 10-30% of the total — so the steel is tuned to be light where the operator wants speed of erection, and robust where the lower chord crosses a highway.

Fatigue is the bridge engineer's constant. While buildings are checked for 2 million wind cycles, a road bridge's welded details are verified for 10-20 million cycles of traffic amplitude (EN 1993-2 with detail categories 36-112 MPa at 2 million cycles), and rail bridges for 50-100 million cycles. The result changes the details: full-penetration welds instead of fillets at splice plates, no sharp cut-outs in gussets, and a relentless minimum-detail-category floor that excludes the cheap tricks used in buildings.

Tolerances of ±2 mm, not ±20 mm. A building frame closes at ±20 mm; a bridge deck that spans a highway closes at ±2-5 mm, because the deck joint, the bearing and the expansion joint must all work at that precision or they wear out — or fail. Our fabrication line for bridges holds member-to-member tolerances of ±1 mm at the bolted splices and ±2 mm overall section depth, with full-size lofts and trial assemblies for every pier segment before shipment.

Erection without falsework over live rivers and roads. A bridge is usually installed without temporary supports beneath it — over a navigable river, a live highway or a rail line. The erection sequence (cantilever, cable-stayed segmental, incremental launching, or full-span lift) is designed so the structure is self-supporting at every intermediate stage, with the erection stresses verified in the design office against the same codes as the final bridge. Our portfolio's 748 m covered bridge was closed with a 24-hour cantilever sequence over the Wei River at Xianyang; every stage was modelled before a single member left the factory.

Corrosion is a life-cycle decision. Bridge steel lives in the atmosphere that attacks it: de-icing salts on the deck, salt spray over tidal waters, industrial SO₂ near plants. The protection system (ISO 12944 C5-M or C5-I, duplex galvanizing + paint, or weathering steel in appropriate climates) is selected for the 100-120 year design life, with the maintenance program (inspection intervals of 1-6 years, repainting at 15-35 years) costed into the client's decision. Repair and replacement access — the walkways, gantries and anchors under the deck — are designed in, not added later.

The bridge is, finally, the proof of a fabricator's claim. Every building we deliver is judged by its owner; every bridge is judged by the public, by the inspectorate and by history. We build bridges the way our name suggests: to the permanent standard, with the numbers that move traffic — and the tolerances that close a 748 m crossing to the millimetre.

The bridge that defines our capability is the Xianyang Covered Bridge over the Wei River — at 748 m, China's first Qin-style two-level steel pedestrian landscape bridge. It is not one span but a sequence of arch-truss units closed by cantilever over the river, with the pedestrian deck, the covered roof and the historically-inspired envelope all integrated into the steel structure. The same bridge line produces interchange and viaduct steelwork for Chinese motorway projects, steel truss bridges for rail corridors, and export bridge steelwork documented to EN 1090-2 EXC3/EXC4 for European instructing engineers.

For infrastructure clients, what matters is the fabrication record: 200,000 tonnes of annual capacity, full-penetration welds 100% UT-tested, ±2 mm member tolerances, and a trial-assembly hall where every pier segment is closed before it ships. When your project document says "NB 25 m clear span deck-type truss, HL-93, EN 1090-2 EXC3, ISO 12944 C5-M," the answer is not whether we can build it — it is which of our 748 m bridge's quality records we will file first.