How bridges get built · Cable-supported and arch bridges · Cable-stayed cantilever erection
Also called: stayed cantilever, cable-stayed deck erection, segment and stay cycle
How it is done
- Complete the pylon and the pier table (the deck segment at the pylon) on falsework or brackets, fix it temporarily to the pylon or pier against unbalanced moment, and install the first stay pairs to a starter section.
- Mount form travellers (concrete deck) or deck cranes and lifting frames (steel or composite deck) at both tips of the balanced cantilever.
- Cycle per segment: cast or lift the segment, connect it (cast joint, welding or bolting), install the stay pair, stress it to the stage force from the construction control analysis, then advance the traveller or crane.
- Survey tip levels, pylon tilt and stay forces after each cycle at a reference temperature (normally at night), feed the results back into the control analysis and adjust the next segment's geometry or stay force.
- Keep the cantilevers within the allowed imbalance; build the side span on piers or falsework where possible and tie it down at the anchor pier; add temporary stays, tie-downs or tuned mass dampers when a long free cantilever is wind-sensitive.
- Close the side spans at the anchor and auxiliary piers, then the main span: pull the tips into line, fit the closure segment at the planned temperature and release the temporary fixity at the pylon.
- Make the final stay adjustment to the target forces after superimposed dead load, install stay dampers and anchorage protection, and record as-built geometry and stay forces as the maintenance baseline.
Key numbers
- Main spanabout 200–1,100 m (record Russky, 1,104 m)
- Pylon height above deckabout 0.2–0.25 of the main span
- Stay spacing at the deckabout 5–10 m for concrete decks, 12–20 m for steel and composite decks
- Deck depthtypically 2–4.5 m, largely independent of span
- Cycle5–10 days per segment and stay pair per cantilever
- Deck and staysUSD 4,000–8,000 per m² of main span (indicative)
Where it fits
- Spans 200-1,100 m over navigable water, valleys and estuaries; steel, composite or concrete decks; anywhere the deck cannot be supported from below.
Where it does not
- Sites where a single pylon cannot be balanced by a side span or anchor pier (the game rejects asymmetric layouts without room for side spans), very high wind without stability studies of the cantilever.
Choosing it
- Choose it over a balanced cantilever box without stays when the span exceeds about 250–300 m: the stays keep the deck shallow and let the cantilever grow without a massive pier section.
- Prefer a suspension bridge above about 1,100–1,200 m, where pylon height and stay length make a cable-stayed scheme uneconomic.
- Use steel or composite decks with deck cranes when segments can be barged in below; concrete decks in travellers when there is no water access for heavy segments.
- Prefer an extradosed bridge for spans of about 100–250 m where pylon height is restricted or a stiffer deck is needed (railways).
Plant, pace and money
PlantForm travellers or deck cranes (200-400 t), barges, stay installation equipment, stressing jacks, survey with GNSS and total stations.
ProductivityOne segment and stay pair per 5-10 days per cantilever; a 400 m main span in 8-14 months after the pylons.
CostDeck and stays USD 4,000-8,000 per m2 of main span; the game's cable-stayed rates.
Risks and controls
What goes wrong
- Cantilever instability in wind or under an unbalanced load, stay force errors accumulating, geometry not closing, traveller or crane anchorage failure, vortex-induced vibration of stays before dampers.
Quality assurance
Stage-by-stage analysis with a construction control programme, stay force measurement by lift-off or vibration, survey after every segment with temperature correction, closure at the planned temperature.
Origins
Strömsund (Sweden, 1956) is taken as the first modern cable-stayed bridge, and the Rhine bridges at Düsseldorf from 1957 developed the stayed cantilever erection cycle; multi-stay concrete decks built in balanced cantilever followed in the 1970s (Brotonne, France, 1977).
Examples
Russky (1,104 m), Sutong (1,088 m), Stonecutters (1,018 m), Pont de Normandie (856 m), Incheon (800 m); the game's pylons and stays follow this sequence in the animation.
Case studies
Russky BridgeRussia · 20121,104 m main span, the cable-stayed record; steel box deck erected in cantilever from pylons about 320 m tall.
Sutong BridgeChina · 20081,088 m main span; steel box segments lifted by deck cranes from barges, with detailed wind studies of the long free cantilever before closure.
Stonecutters BridgeHong Kong, China · 20091,018 m main span: twin steel box deck in the main span lifted from barges, concrete back spans built on intermediate piers.
Pont de NormandieFrance · 1995856 m main span, a record at opening: concrete cantilevers from each pylon carried 116 m into the main span, the 624 m central part being steel segments erected in cantilever.
In the bridge game
What Bridge Master applies when you pick it
Deck types: Cable-stayed, Extradosed, Orthotropic steel box, PSC box, balanced cantilever. Spans 200-800 m, up to 1100 m.
- +30: The way cable-stayed bridges are built.
- -10: Temporary tie-downs and wind tunnel tests of construction stages.
- +10: Free cantilevering keeps the shipping lane open.
Related methods
Stay cable installation and tensioningPylon construction: concrete, anchorage zones and geometryBalanced cantilever, cast in place (form travellers)Cantilever erection of steel (derrick and lifting frames)Extradosed bridge construction
Further reading
Gimsing and Georgakis · PTI DC45.1 · fib Bulletin 30 Acceptance of stay cable systems · Svensson, Cable-Stayed Bridges: 40 Years of Experience Worldwide · Walther et al., Cable Stayed Bridges (Thomas Telford)