Construction methods · Cast-in-place concrete decks

Full staging method (ground falsework)

Formwork supported on scaffold towers or a timber and steel falsework grid built up from the ground; the deck is cast in place span by span or all at once. Cheapest for short bridges over dry, firm ground with no traffic below, and the origin of every other cast-in-place method.

How bridges get built · Cast-in-place concrete decks · Full staging method (ground falsework)

Also called: FSM, falsework, conventional cast-in-place, scaffold construction

deck cast in place on the formworktowers on blinding or sleepers on dry firm groundFull staging method (ground falsework)
Concept diagram (TheBridgeEng)

How it is done

  1. Prepare the ground: compact, blind with concrete or sleepers, or drive short piles if soft.
  2. Erect proprietary towers or heavy-duty props with a grid of steel beams; set the soffit formwork to the design camber including falsework settlement.
  3. Fix reinforcement and tendons, pour in a planned sequence (midspans before supports for continuous decks), cure, stress, then strike from midspan outward.
  4. Preload or pre-compress falsework on soft ground; monitor settlement during the pour.

Where it fits

  • Spans 10-50 m, deck height under about 15 m, dry ground, overpasses closed to traffic below, culvert-type crossings, short valley viaducts.

Where it does not

  • Water (the game's crane_ground and falsework checks), live roads and railways below, soft clay under towers, tall decks.

Plant, pace and money

PlantFalsework towers or props, steel beams, formwork, concrete pump, mobile crane.
Productivity30-45 days per span for the full cycle; faster with two sets of falsework.
CostFormwork and falsework USD 150-300 per m2 of deck; total deck USD 900-1,600 per m2.

Risks and controls

What goes wrong

  • Falsework collapse during the pour is the leading cause of fatalities in concrete bridge construction; settlement of tower foundations; premature striking.

Quality assurance

Independent temporary works design and check, foundation bearing verification, pre-pour inspection with a hold point, settlement monitoring during pouring.

Examples

Most short concrete overpasses; in the game it is the default for short dry spans and is barred in water and over rail.

In the bridge game

What Bridge Master applies when you pick it

Deck types: RC slab, Voided slab, RC T-beam, RC box, PSC box (cast in place), Rigid frame, Concrete arch, PSC box, balanced cantilever, Extradosed, Network tied arch. Spans 10-50 m, up to 70 m.

  • +25: Dry firm ground, low deck: falsework is the cheap answer.
  • -50: No falsework in water.
  • -50: No falsework over track.
  • -40: No falsework over live lanes unless the road can close.
  • -30: Tall towers get expensive and unstable.
  • -20: Falsework foundations settle on soft ground.
  • -15: Long viaduct: MSS or precast is faster.
  • not allowed: Ground falsework in a river.
  • not allowed: Ground falsework over a live railway.

Try it in the game →

Related methods

Falsework on temporary piles (shallow water)Movable scaffolding system (MSS)Falsework and temporary works engineeringCast-in-place post-tensioned box and slab decks

Further reading

BS 5975 · ACI 347 · Scaffold, Shoring and Forming Institute guides

Falsework on temporary piles (shallow water) →