How bridges get built · Precast concrete decks · Spliced precast girders on temporary towers
Also called: spliced girder bridge, haunched precast girder, long-span precast girder
How it is done
- Cast pier segments with haunches and drop-in segments in the yard; transport in lengths of 40-50 m.
- Erect pier segments on the piers with temporary towers or strongbacks; set drop-in segments between them.
- Cast the splice joints, thread and stress the full-length tendons, remove the towers.
Where it fits
- Spans 45-90 m over roads and shallow water, sites where a crane can stand but a cast-in-place box would be slow, three-span river bridges.
Where it does not
- Deep water at tower positions, spans over about 90-100 m.
Plant, pace and money
PlantLarge crawler cranes, temporary towers or strongbacks, PT equipment.
ProductivityTwo to four weeks per span.
CostDeck USD 1,300-2,000 per m2.
Risks and controls
What goes wrong
- Tower settlement, girder stability before splicing, splice quality, staged post-tensioning errors.
Quality assurance
Tower foundation check, geometry survey before splicing, stressing records.
Examples
Florida and Washington State spliced girder bridges; Korean IPC girders.
In the bridge game
What Bridge Master applies when you pick it
Deck types: Spliced PSC girder, PSC I-girder, PSC U-girder, Steel plate girder. Spans 45-80 m, up to 100 m.
- +30: The method for spliced girders.
- -20: Deep water towers are expensive; use strongbacks.
- -15: Towers in the rail corridor are hard; strongbacks only.
Related methods
Crane erection of precast girdersBalanced cantilever, cast in place (form travellers)Post-tensioning: tendons, stressing and grouting
Further reading
PCI Spliced Girder Guide · NCHRP Report 517