Construction methods · Steel erection

Orthotropic steel decks

A steel deck plate stiffened by longitudinal closed ribs and transverse floor beams, forming the top of a box girder and carrying traffic directly on a thin surfacing. The lightest deck there is, so long-span cable-stayed and suspension bridges use it; fatigue at the rib-to-deck welds and surfacing debonding are its lifelong issues.

How bridges get built · Steel erection · Orthotropic steel decks

Also called: orthotropic deck, steel deck plate, closed rib deck

How it is done

Fabricate deck panels with ribs welded by automated processes (80 % partial penetration or full), inspect with phased-array UT.
Assemble panels into box sections in the shop or a site yard; erect by cantilever, floating crane or strand jack.
Weld the deck plate splices on site with backing bars; grind and inspect.
Apply the surfacing: epoxy asphalt, Gussasphalt or a bonded thin polymer overlay, on a blasted and primed plate.

Where it fits

Suspension and cable-stayed main spans, movable bridges, deck replacements where weight must fall.

Where it does not

Heavy-truck routes without adequate plate thickness (14 mm was too thin; 16-18 mm is current), poor surfacing bond.

Plant, pace and money

PlantAutomated welding lines, large-section transport, floating or deck cranes, UT inspection.

ProductivityPanel production is shop-driven; site welding a few splices per day.

CostUSD 6,000-10,000 per tonne fabricated; deck USD 2,500-4,000 per m2.

Risks and controls

What goes wrong

Fatigue cracks at rib-deck and rib-floorbeam welds, surfacing failure, distortion from site welding.

Quality assurance

Weld penetration verified by macro tests, phased-array UT on 100 % of rib welds where required, surfacing bond tests.

Examples

Akashi Kaikyo, Great Belt, Sutong, Russky; the game's steel_box_orthotropic type.