Climbing and jump formwork

How bridges get built · Piers, pylons and abutments · Climbing and jump formwork

Also called: jump form, self-climbing formwork, crane-climbing formwork

Climbing and jump formwork — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Cast the first one or two lifts conventionally and set the climbing anchors (cast-in cones or bolts) in the last lift at the bracket positions on the climbing drawings.
Mount the brackets or rails on the anchors and build the platforms: reinforcement deck above, main working deck at form level, and a trailing finishing platform below for anchor recovery and patching.
Cycle: fix reinforcement and embeds (prefabricated cages where possible), set the next anchors, close and plumb the forms, pour the 4–5 m lift and strip.
Climb only when the concrete at the new anchors has reached the supplier's minimum strength: crane-climbing units are lifted as complete units, self-climbing units jack their rails and brackets up on hydraulic cylinders without the crane.
Adjust the panels for taper, wall-thickness changes and inclination; inclined pylon legs need temporary struts or ties until the cross beam is built.
Survey every lift for position, verticality and twist at a fixed time of day (early morning) with temperature correction, and correct drift gradually over several lifts.
Observe hold points before each climb (anchor record, platforms cleared of stored material, wind below the climbing limit); at the top, dismantle by crane and make good the anchor holes.

Key numbers

Lift height3–6 m, most often 4–5 m
Cycle3–5 days per lift on plain shafts, 5–8 days in congested pylon anchorage zones
Economic above about 25–30 m height
Concrete strength at the anchors before climbing: typically about 10–20 MPa, as the supplier specifies
Verticalityabout 1/1,000 of the height for piers, with tighter targets on tall pylons

Where it fits

Piers over 25 m, valley viaducts, concrete pylons of 60-300 m, inclined pylon legs (with tie-backs during construction).

Where it does not

Short piers, where the setup costs more than it saves.

Choosing it

Choose climbing over slipform when the section changes, embeds and anchorages are dense, lift joints are acceptable, or the site cannot run continuously 24 hours a day.
Choose self-climbing over crane-climbing when the crane is the bottleneck (several legs, tall pylons) or wind often stops crane lifts of large units.
Prefer conventional lifts below about 25 m height or for a handful of piers.
Prefer slipform for tall, constant-section shafts with a crew and concrete supply able to run without stops.

Plant, pace and money

PlantClimbing system (Doka, Peri or similar), tower crane or self-climbing hydraulics, concrete pump with placing boom.

ProductivityOne 4-5 m lift per 4-7 days per leg; a 150 m pylon in 8-12 months.

CostUSD 600-1,200 per m3 of pylon concrete including the system.

Risks and controls

What goes wrong

Anchor failure during climbing, wind on platforms, geometry drift accumulating over the height, cable anchorage zones with congested reinforcement.

Quality assurance

Survey of every lift (verticality within height/1,000 or better), anchor cone tests, reinforcement cover checks, temperature control in thick sections.

Origins

Climbing forms grew out of shaft, chimney and dam construction; crane-climbed bracket systems were common on tall bridge piers by the 1960s and 1970s, and hydraulic self-climbing systems became normal on tall piers and pylons from the 1990s.

Examples

Millau (245 m piers), Sutong and Russky pylons, Incheon Bridge pylons; the game's pylon duration is based on lift cycles.

Case studies

Millau ViaductFrance · 2004Concrete piers up to 245 m (pier P2) climbed in lifts of about 4 m; each pier splits into two thinner shafts for its top 90 m.

Russky Bridge, VladivostokRussia · 2012A-shaped concrete pylons 320.9 m high, climbed lift by lift in a harsh winter climate for a 1,104 m cable-stayed span.

Willow Island cooling towerUSA · 1978Not a bridge, but the defining climbing-form accident: 51 workers died when the climbing scaffold fell because the concrete holding its anchors was too young.