Construction methods · Piers, pylons and abutments

Pylon construction: concrete, anchorage zones and geometry

A pylon is a tall pier with a cable anchorage zone at the top: the concrete legs climb with jump forms, the cross beams are cast on brackets or lifted as steel, and the stay anchorages are steel boxes or corrugated pipes embedded in a congested, heavily post-tensioned zone. Geometry control is the whole game: the pylon must be where the cables expect it.

How bridges get built · Piers, pylons and abutments · Pylon construction: concrete, anchorage zones and geometry

Also called: tower construction, cable-stayed pylon, pylon anchor box

Pylon construction: concrete, anchorage zones and geometry — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Climb the legs in 4-5 m lifts; for inclined legs, install temporary ties between the legs or to the ground until the cross beam is cast.
Cast cross beams on bracket-supported formwork or lift prefabricated steel beams.
In the anchorage zone, install the steel anchor boxes or pipes lift by lift with the deviator plates surveyed to millimetres; add the transverse post-tensioning that holds the anchorage zone together.
Finish with the saddle or the top anchorage, the maintenance lift and access.

Where it fits

Concrete pylons of 60-300 m; H, A, inverted-Y and diamond shapes.

Where it does not

Skipping the temporary ties on inclined legs; skipping the lift-by-lift survey.

Plant, pace and money

PlantClimbing forms, tower crane of 100-300 m hook height, concrete pump with placing boom, survey with prisms and GNSS.

Productivity8-14 months for a 150-200 m pylon per leg pair.

CostUSD 30-120 million per pylon depending on height.

Risks and controls

What goes wrong

Geometry error accumulating (cables then need adjustment), cracking in the anchorage zone, wind on the free-standing legs before the cross beam, crane capacity for the anchor boxes.

Quality assurance

Daily survey with temperature correction, anchor box position within 5-10 mm, post-tensioning records.

Examples

Sutong (306 m), Russky (320 m), Incheon (238 m), Stonecutters (298 m, composite top).