Paul Liles is the state bridge engineer for Georgia DOT and chairman of AASHTO’s T6 committee, a technical committee focused on FRP. The group is responsible for design specifications on structures including bridges and walls. Liles says that while the composites industry hoped to take off in all facets of bridgework, only some areas have seen success.
How does the T6 Committee work?
The T6 is a technical committee for FRP. It consists of nine to 10 people, generally state employees and members of state DOTs. The committee is responsible for design specifications (specs) in regards to structures. That includes not only bridges, but also other structures such as walls. We meet once a year and discuss specifications and use of composites, current research and successful/unsuccessful projects. We’ll move those specs forward if we feel there’s a lot of activity in the area it relates to.
What help does the T6 Committee get from industry?
We receive institutional knowledge from composite industry researchers, schools and some companies who present studies they’ve completed. Researchers will come and make a presentation. We tell them to write a spec, which mainly details what formulas and safety factors to include in the design. Or industry comes in and says it’ll write a spec, and we’ll vote on bringing it forward. It goes to the overall bridge committee and it gets voted on. If it passes, AASHTO prints it out as a specification for design.
How did composites enter the bridge market?
When composites first came out, everyone said it was the greatest thing. We had people say composites would solve a lot of problems. The federal government pushed products, which resulted in program-sponsored innovative materials. But those people weren’t engineers, and were caught up in the enthusiasm of those possibilities rather than the reality of what the material could accomplish.
What ideas did states have for composites?
Decks, complete bridges, rebar, repairs with carbon wraps, earthquake mitigation and a whole gamut of things. As it turned out, a lot of these ideas were expensive. As a result, interested companies would come and go, but the ones that took off were those involved in wraps and repairs. It filled a huge need for deterioration, and took off because it was cost-effective. When a contractor damages a beam, repairing with carbon fiber is the cheapest thing for them to do. However, there are some questions about how long the repair will last. The industry tells us different amounts, from 15 to 25 years for exposed conditions, and we don’t know. It’s been out for 10 to 15 years, but we’ve seen no reports of taking it down.