Spliced precast girders on temporary towers

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

Lay out the segments (haunched pier segments, drop-in and end segments) with splices near points of low moment and continuous ducts that line up through the joints.
Cast the segments in the plant with pretensioning for handling and early loads, holding duct positions with mandrels so they align at the splices.
Erect the pier segments on the piers with temporary towers or bracing for stability, and the end segments on the abutments and temporary towers.
Set the drop-in segments on strongbacks hung from the adjacent segments or on temporary towers, and brace all girder lines together.
Align and couple the ducts, form and cast the splice joints and diaphragms, and cure them to the specified strength.
Stress the full-length tendons in the designed stages (some before and some after the deck is cast) and grout them.
Release and remove the temporary towers and strongbacks, survey the profile, and cast the deck or the rest of it and the barriers.

Key numbers

Span45–90 m (Highland View 76 m main span; Texas spliced I-girders up to about 91 m)
Segment lengthusually limited by road transport, about 45 m (150 ft) in Texas practice
Segment weightdesigned for lifts of about 90 t (100 US tons) in Texas practice
Cycle2–4 weeks per span
Costdeck USD 1,300–2,000 per m2

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.

Choosing it

Choose spliced girders over steel plate girders or a cast-in-place box for 45–90 m spans when a precast plant is within reach, cranes can stand, and post-tensioning skills are available.
Prefer steel girders when temporary towers cannot be placed, or when segment weights or lengths exceed transport limits.
Prefer balanced cantilever above 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.

Origins

Splicing precast girders with post-tensioning grew in US practice in the 1980s and 1990s to carry precast girders past the single-piece transport limit; Florida's Highland View Bridge (reported in 1994) then had the longest concrete girder span in the US at 76 m, and NCHRP Report 517 (2004) consolidated the design practice.

Examples

Florida and Washington State spliced girder bridges; Korean IPC girders.

Case studies

Highland View Bridge (US 98 over the Gulf Intracoastal Waterway)USA · early 1990s76 m (250 ft) main span of continuous post-tensioned bulb-tee girders with spliced drop-in segments, reported as the longest concrete girder span in the US at the time.

Sargent Beach bridge, Matagorda County, TexasUSA · 2011–2024 (TxDOT programme)91 m (300 ft) main span in a 210 m unit of spliced I-girders, haunched over the supports and erected on shoring towers with internal strongbacks.

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.
-30: Towers in the navigation route: the channel span must be closed with strongbacks or lifted whole.
not allowed: Temporary towers in the water where in-water works are banned.

Try it in the game →