Construction methods · Steel erection

Cantilever erection of steel (derrick and lifting frames)

Steel trusses and box girders are built outward from a pier as a cantilever, each new piece lifted by a derrick or creeper crane that rides on the already-erected structure. The great method of cantilever trusses and of long-span steel over navigable water; still used for trusses and for the main spans of cable-supported steel decks.

How bridges get built · Steel erection · Cantilever erection of steel (derrick and lifting frames)

Also called: cantilever steel erection, creeper crane, derrick crane erection, traveller erection of steel

derrick cranenext panel from a bargeCantilever erection of steel
Concept diagram (TheBridgeEng)

How it is done

  1. Erect the pier section on the pier with a floating crane or by falsework; install the traveller or derrick crane on top.
  2. Lift pieces delivered by barge or along the deck; bolt or weld the connections; advance the crane each panel; balance the cantilevers on both sides or tie back to the anchor span.
  3. Close at midspan with a suspended span lowered between the cantilevers or by jacking the tips to fit.

Where it fits

  • Steel trusses of 150-500 m, box girder main spans over navigation routes, steel arches erected as cantilevers with tie-backs, cable-stayed steel decks.

Where it does not

  • Sites where a floating crane can lift the whole span in one go; short spans.

Plant, pace and money

PlantDerrick or creeper cranes (100-500 t), barges, temporary tie-backs, jacking systems for closure.
ProductivityOne panel (10-15 m) per two to five days per cantilever.
CostErection USD 800-1,500 per tonne.

Risks and controls

What goes wrong

  • Overturning of the cantilever, connection slip, closure misfit from temperature, crane derailment (the 1907 Quebec Bridge collapse remains the lesson).

Quality assurance

Stage-by-stage analysis with temporary conditions, daily survey of the tip, bolt inspection, closure at the planned temperature.

Examples

Forth Bridge, Quebec Bridge (completed 1917), Japanese Minato Bridge, Chinese Yangtze truss bridges.

In the bridge game

What Bridge Master applies when you pick it

Deck types: Steel truss, Steel box girder, Orthotropic steel box, Steel arch, Cable-stayed, Extradosed, Steel plate girder. Spans 100-300 m, up to 550 m.

  • +30: Long steel truss or arch: cantilever erection.
  • +15: Keeps the channel open.
  • -30: Simpler methods.

Try it in the game →

Related methods

Crane erection of steel girdersTruss assembly and erectionCable-stayed cantilever erectionArch erection by cantilever with temporary stays

Further reading

Troitsky, Cable-stayed Bridges · Japanese steel bridge erection standards

← Launching of steel girders and boxesField splices: bolted and welded connections →