Construction methods · Finishing, articulation and maintenance

Deck replacement and widening

The deck slab wears out first: chlorides, freeze-thaw, traffic. It is replaced in stages under traffic, or overnight with full-depth precast panels, while the girders are kept; widening adds girders and a new slab alongside, tied to the old with dowels and a longitudinal joint.

How bridges get built · Finishing, articulation and maintenance · Deck replacement and widening

Also called: redecking, deck rehabilitation, bridge widening

Deck replacement and widening — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Staged: close half the width, hydro-demolish the slab from the girders, replace the shear connectors, cast the new slab, switch traffic, repeat.
Panel replacement: remove slab sections at night, set full-depth precast panels with grouted pockets, reopen by morning.
Widening: new foundations and piers or extended caps, new girders, new slab with a wet joint to the old, matching camber.

Where it fits

Decks past 40-60 years in de-icing climates, bridges needing more lanes, girders still sound.

Where it does not

Redecking girders with unknown condition; widening on piers that cannot take the extra load without strengthening.

Plant, pace and money

PlantHydro-demolition, cranes, precast panels, traffic management.

ProductivityStaged redecking a span per month; panels a span per week of nights.

CostUSD 400-900 per m2 of deck replaced.

Risks and controls

What goes wrong

Girder damage during demolition, traffic loading on a half deck, differential settlement between old and new.

Quality assurance

Girder inspection after demolition, connector installation records, camber matching.

Examples

US interstate redecking programmes; Korean expressway widening from four to six lanes.