How bridges get built · Piers, pylons and abutments · Precast segmental piers and caps
Also called: prefabricated substructure, precast column segments, ABC substructure
How it is done
- Cast column segments (1.5-6 m) and caps with match-cast joints and ducts for post-tensioning, or with grouted couplers for the bars.
- Set the first segment on the footing with a levelling shim and grout bed; stack segments with epoxy joints; stress vertical tendons through the pier.
- Set the precast cap with grouted pockets or couplers; grout and cure before loading.
Where it fits
- Long viaducts with repetitive piers, urban and railway sites with short closures, marine viaducts where site work is expensive, seismic regions with proven connection details.
Where it does not
- Piers that all differ, very tall piers, sites without a yard or a heavy crane.
Plant, pace and money
PlantPrecast yard, transport, 200-500 t crane, stressing and grouting plant.
ProductivityA pier in one to three days on site versus two to three weeks cast in place.
Cost10-25 % more per pier than cast-in-place; recovered in time and in reduced site risk.
Risks and controls
What goes wrong
- Joint grout quality, duct blockages, tolerance stacking, connection performance in earthquakes.
Quality assurance
Match-cast records, grout tests, tendon stressing, connection mock-ups for seismic details.
Examples
Hong Kong-Zhuhai-Macau approaches, Florida and Texas ABC projects, Korean coastal viaducts.
In the bridge game
What Bridge Master applies when you pick it
Deck types: any. Spans 20-60 m, up to 100 m.
- +30: Precast piers assembled in days.
Related methods
Cast-in-place piers with formwork liftsLateral slide (slide-in bridge construction)SPMT move (self-propelled modular transporters)
Further reading
FHWA ABC Manual · PCI Bridge Design Manual Chapter 16 · AASHTO Guide Specifications for ABC