Construction methods · Precast concrete decks

Balanced cantilever with precast segments

Match-cast segments are lifted from barges or trucks by a deck-mounted lifting frame, a crane or a launching gantry, glued and stressed symmetrically from each pier, two to four segments a day per pier. The fast way to build 60-150 m spans in quantity.

How bridges get built · Precast concrete decks · Balanced cantilever with precast segments

Also called: precast segmental cantilever, segmental balanced cantilever, lifting frame erection

How it is done

  1. Cast segments long-line or short-line with epoxy-matched faces; store and deliver.
  2. Place the pier segment; erect segments in pairs each side with a lifting frame or gantry; epoxy, temporary bars, stress cantilever tendons per pair.
  3. Close at midspan with a cast-in-place closure; stress continuity tendons; remove temporary fixity.

Where it fits

  • Spans 60-150 m over water and roads with many similar spans; marine viaducts where barges deliver segments; sites needing speed.

Where it does not

  • Few spans (the yard costs), spans over 150 m (segment weight and cantilever), sites where segment delivery is impossible.

Plant, pace and money

PlantCasting yard, lifting frames or gantry, barges or transporters, PT plant.
ProductivityTwo to four segments per day per pier; a 100 m span pair in 3-5 weeks.
CostDeck USD 1,600-2,600 per m2.

Risks and controls

What goes wrong

  • Unbalanced moment during erection, epoxy joint quality in heat or rain, segment geometry error, lifting frame anchorage.

Quality assurance

Geometry control from the yard through erection, epoxy tests, stressing records.

Examples

Confederation Bridge (250 m, precast), Hong Kong-Zhuhai-Macau, Incheon approaches, US Gulf coast bridges.

In the bridge game

What Bridge Master applies when you pick it

Deck types: Precast segmental box, Extradosed, Cable-stayed, PSC box, balanced cantilever. Spans 60-130 m, up to 150 m.

  • +30: Several medium-long spans: precast cantilever.
  • +15: Segments arrive by barge.
  • -30: Too few spans for a casting yard.
  • -40: Beyond precast cantilever.
  • -25: Span-by-span is faster at short spans.
  • not allowed: Precast cantilever beyond feasibility.

Try it in the game →

Related methods

Balanced cantilever, cast in place (form travellers)Span-by-span precast segmental with gantrySegment casting: short-line and long-line match castingFloating crane erection

Further reading

ASBI Handbook · Podolny and Muller

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