The Harkers Island Bridge in North Carolina is one of the clearest real-world proofs that GFRP rebar can carry a full coastal bridge. Opened in December 2023, the 3,200 ft, 28-span crossing has no steel reinforcement in its primary load-carrying parts. Engineers used GFRP bars and carbon fibre (CFRP) strands instead, and doubled the design life from 50 to 100 years.
Here is what was built, why steel was left out, and what Indian engineers and contractors can take from it.
Quick facts: Harkers Island Bridge
| Item | Detail |
|---|---|
| Location | Harkers Island, North Carolina, USA |
| Owner | North Carolina Department of Transportation (NCDOT) |
| Length | 3,200 ft, 28 spans |
| Reinforcement | GFRP bars + CFRP prestressing strands; no steel rebar in primary elements |
| GFRP used in | Deck, girder stirrups, pile caps, pier columns |
| Design life | 100 years, up from 50 |
| Opened | December 2023, nearly a year ahead of schedule |
Sources: NCDOT research report, PCI project profile, Roads & Bridges.
Why the old steel bridges failed
Harkers Island has only one road to the mainland, so its bridge is a lifeline. The 1941 bridge lasted just 27 years. Its 1969 replacement, also steel-reinforced concrete, faced the same salt-water attack (Roads & Bridges).
The mechanism is simple. Chlorides from seawater and salt spray reach the steel through the concrete cover. The steel rusts and expands, cracking and spalling the concrete. Every crack lets in more salt, and the damage speeds up.
Coatings, thicker cover and inhibitors only delay this. NCDOT chose to remove the steel instead.
How the reinforcement was split: GFRP vs CFRP
The project did not use one material for everything. Each was placed where it works best:
- GFRP bars handled ordinary (non-prestressed) reinforcement: the cast-in-place deck, girder stirrups, pile caps and pier columns.
- CFRP strands handled prestressing in the precast girders and piles, where bars sit under very high sustained tension.
This split matters. GFRP is excellent as normal reinforcement, but codes limit how much sustained stress it can carry long-term. CFRP is stronger and stiffer, and costs far more, so it was used only where needed.
For most Indian projects, decks, slabs, walls, piers and footings fall in the GFRP zone. That is where the bulk of the reinforcement tonnage sits.
What changed on site
The contractor, Balfour Beatty, reported practical gains beyond corrosion (source):
- GFRP weighs about a quarter of steel, so handling was faster and safer.
- Bars arrived pre-bent from the factory, so no bending was needed on site.
- The bridge opened nearly a year early, helped by precast piles and girders.
Working on a bridge deck, jetty or coastal slab? Use our free GFRP slab and deck calculator to estimate bar quantity, or send us your bar schedule for a GFRP conversion check.
Lessons for bridges and coastal projects in India
India's coastline sees the same chemistry as North Carolina, with more heat and humidity. Gujarat alone has the country's longest coastline, lined with ports, jetties, salt works and chemical clusters.
Three lessons carry over directly:
- Design for service life, not day-one cost. Harkers Island doubled its design life. Our lifecycle cost analysis of GFRP vs steel shows how that changes the real cost.
- Use GFRP where corrosion decides life. Decks, piers, pile caps, coastal structures and ports and harbours are the strongest fits. See also GFRP rebar for bridges and flyovers.
- Back the material with test data. NCDOT ran a full research programme. In India, insist on a valid BIS licence under IS 18256:2023 and recent type-test reports. Check the list of BIS licensed GFRP rebar manufacturers before you buy.
RN Elements manufactures GFRP rebar in Surat, Gujarat, certified to IS 18256.
Where GFRP is not the right fit
GFRP is not a drop-in swap for steel everywhere. A good design checks three things:
- Stiffness. GFRP has a lower elastic modulus than steel, so deflection and crack width often govern the design.
- Bending. Bars cannot be bent on site; bends and stirrups must be factory-made to the bar schedule.
- Fire. The resin softens at high temperature, so fire-rated elements need extra cover or another solution.
Often the best answer is a hybrid: GFRP in zones exposed to salt and water, steel where corrosion risk is low.
Frequently asked questions
Can GFRP rebar be used in bridges? Yes. GFRP bars are used in bridge decks, barriers, pile caps and piers worldwide. Harkers Island used GFRP in every primary element except the prestressing.
Can GFRP replace prestressing steel? Generally no. Prestressing needs very high sustained tension, which is why Harkers Island used CFRP strands for that role and GFRP for ordinary reinforcement.
How long does a GFRP-reinforced bridge last? Harkers Island was designed for 100 years, double its steel-reinforced predecessor, because the reinforcement cannot corrode.
Is GFRP rebar approved in India? Yes. BIS IS 18256:2023 covers GFRP bars for concrete reinforcement. Check that your supplier holds a BIS licence, not just a claim of compliance.
Get a GFRP check for your project
Planning a bridge, jetty, sea wall or coastal building? Our engineering team will review your drawings or bar schedule and tell you where GFRP fits, and where it doesn't.