Michigan DOT Research: Carbon Fiber Prestressed Bridge Beams

An MDOT-led research partnership is putting next-generation bridge beams to the test.

Michigan Department of Transportation

Carbon fiber reinforced polymer, or CFRP, is changing the way bridges are built. It can be braided into long strands of varying thickness and added to concrete structures to increase support and durability. Its strength is comparable to steel, which has traditionally been the go-to material for reinforcing concrete. But while steel is prone to rusting over time, CFRP is corrosion-resistant. This means that in a climate like Michigan's – with cycles of scorching-hot summers and frigid winters with rust-inducing deicing treatments – those structures reinforced with CFRP tend to last longer than those that are built with steel.

Joining efforts with three other states, Maine, North Carolina and Ohio, MDOT created  TPF-5(363)  in 2017 to study the capabilities and limitations of a new CFRP product, 0.7-inch-diameter strands. The study partners with the research team at Lawrence Technological University, which will embed the CFRP strands into concrete bridge beams, then subject the beams to a series of stress tests.

The project will follow MDOT's  similar research  investigating the abilities of 0.6-inch-diameter CFRP strands.

That groundbreaking study, which took place from 2013 to 2019, earned MDOT an  AASHTO Sweet 16 award in 2020 . To understand how 0.6-inch CFRP strands would perform over time in a variety of real-world scenarios, the same team at Lawrence Technological University added the strands to standard concrete bridge beams, then pushed those beams to their limits.

The new pooled fund study will build upon this previous work – and employ many of the same stress tests – using the newly developed 0.7-inch-diameter strands.

If, as expected, these new strands prove to be stronger than the previously studied strands, it could mean a revolution in bridge design.

With more strength per strand, MDOT engineers hope to need less of it to achieve a bridge's desired load requirements – leading eventually to lighter, stronger bridges that require less maintenance over time.

Our goal in Michigan has long been to design bridges with 100-year service lives. Now, CFRP gets us one step closer.— Matt Chynoweth, former MDOT Chief Bridge Engineer

For more information about MDOT’s participation in this pooled fund, please contact:

André Clover,  CloverA@Michigan.gov , 517-749-9001

Steve Kahl,  KahlS@Michigan.gov , 517-898-3428

The Transportation Pooled Fund Program

Investing in pooled fund studies through the  Transportation Pooled Fund Program  helps MDOT leverage its research dollars to support a wide range of functional areas throughout the agency.