Construction methods · Precast concrete decks

Full-span precast erection (high-speed rail type)

Complete 25-40 m box spans of 600-900 t are cast in a yard, carried along the finished deck by a rubber-tyred carrier and set on the next pier pair by a launching gantry. One span per shift and kilometres per year: the viaduct method of Chinese, Taiwanese and Korean high-speed rail.

How bridges get built · Precast concrete decks · Full-span precast erection (high-speed rail type)

Also called: full-span method, FSM precast, span carrier and launching gantry

How it is done

  1. Build a casting yard with 8-12 moulds, steam curing and a stacking area near the alignment.
  2. Load a span on the carrier (900 t class); drive along the completed deck to the gantry; the gantry lifts the span, moves it forward and lowers it onto the bearings.
  3. Cycle daily; the yard keeps ahead by several spans.

Where it fits

  • Straight or gently curved viaducts with hundreds of identical spans, rail, flat terrain, no ground access.

Where it does not

  • Fewer than about 100 spans (the yard and carrier cannot be amortised), spans over 40-45 m, tight curves, tall piers beyond gantry reach.

Plant, pace and money

PlantCasting yard, span carrier, launching gantry (900 t class), steam curing.
ProductivityOne span per shift; 10-20 km of viaduct per year per set.
CostDeck USD 900-1,400 per m2 at high-speed-rail scale; uneconomic below it.

Risks and controls

What goes wrong

  • Gantry and carrier overturning, mould geometry error repeated hundreds of times, span cracking during transport.

Quality assurance

Mould survey, curing records, span camber and dimensions before dispatch, gantry procedures.

Examples

Beijing-Shanghai high-speed rail, Taiwan HSR, Honam and Suseo HSR in Korea.

In the bridge game

What Bridge Master applies when you pick it

Deck types: Full-span precast box, PSC U-girder, PSC I-girder. Spans 25-40 m, up to 45 m.

  • +35: Kilometres of 30-55 m spans: gantry span-by-span.
  • +15: Marine or urban viaduct with no ground access.
  • -40: Gantry and yard cannot be amortised.
  • -40: Beyond span-by-span.
  • -20: Gantry geometry on tight curves is awkward.
  • not allowed: Span-by-span gantry beyond feasibility.

Try it in the game →

Related methods

Span-by-span precast segmental with gantryLaunching girder (beam launcher) for precast girdersPrecast segmental piers and caps

Further reading

Chinese TB standards for HSR viaducts · Taiwan HSR construction papers

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