Photo: Jacob Wittrup Schmidt.

New invention may extend the life of bridges

Monday 29 Apr 19
by Line Reeh

Facts about carbon fibre composites

  • Can be used to reinforce bridges, silos and similar structures onshore and offshore.

  • Weighs only 20 per cent of steel and has a tensile strength that is five times higher.

  • Has very high corrosion resistance.

  • Is typically used as reinforcement bars (circular, square, etc.), strips, or cloth in the construction industry. Carbon fibre bars/strips are mounted on the existing structure (for example a concrete bridge deck) by gluing it on to the surface or by milling it into the structure.

  • May potentially also be used in new structures as non-tensioned or prestressed reinforcement.
A new anchoring system for carbon fibre reinforcement which is five times stronger than steel reinforcement will be able to extend the service life and carrying capacity of concrete structures.

Associate Professor Jacob Wittrup-Schmidt—DTU Civil Engineering—is the researcher behind a new anchoring system for carbon fibre reinforcement which can be used to reinforce and extend the service life of bridges, silos and other structures. The system can provide tensile strengths five times higher than steel reinforcement and creates the possibility of early warning of fractures—traditionally the Achilles’ heel of carbon fibre reinforcement.

A patent application has just been submitted for the invention, and the development of the invention is now being continued in a partnership with the company S&P Reinforcement Nordic, owned by the American company Simpson Strong-Tie. The company—which works in 50 countries with extension of the service life of buildings and bridges—sees major prospects in Jacob Wittrup-Schmidt’s research:

“On a European scale, the use of carbon fibre reinforcement has increased significantly in the past decade, and this trend looks set to continue, also outside Europe. The aviation, automotive, and wind turbine industries have been by far the biggest buyers. Based on our nearly 25 years of experience in this field, we see a huge potential and have great expectations for the new product. We’re really looking forward to putting the system into production and use,” says Morten Frost Kamphøvener, engineer and Nordic Sales Manager in S&P Reinforcement Nordic.

Retains carbon fibre strength
Innovative anchoring mechanisms for carbon fibre reinforcement are the core of the patented inventions. The anchoring solves the problem that carbon fibre has a high tensile strength in the direction of the fibre, but is very vulnerable to transversal impacts. This makes it challenging to anchor the reinforcement without concurrently reducing carbon fibre strength, according to Associate Professor Jacob Wittrup-Schmidt:

“With our new anchoring methods, we can check the impact of the anchoring on the carbon fibre composite, so that it does not lose strength due to inexpedient anchoring. At the same time, we can design the anchoring to enable improved early warning of the fracture types before the maximum load is reached, which makes the mechanism incredibly interesting, also from a safety perspective.”
Another objective has been that the anchoring must be easy and quick to mount on a structure, so that the time used and any derived traffic inconvenience—for example in connection with work on a bridge—are minimized.

The research behind the innovative solutions is based on advanced modelling and experiments in the newly expanded test facilities at DTU Civil Engineering.

“An evaluation is currently being done of test and theory which are to be verified and gone over thoroughly by the collaboration partners. In addition, international articles and documentation will be prepared, and the mechanism will be tested by external parties. The objective is that the first solution will be presented in 2019,” explains Jacob Wittrup-Schmidt.

Test on steel structures in the near future
The new reinforcement method is designed for concrete structures, but is expected also to be tested as reinforcement of steel structures in the near future.

One of the locations for these tests will be at EMPA in Switzerland, which is one of the leading test facilities in the world. Leader of ‘Sustainable Metallic Structures (SUMS)’ group at EMPA—Elyas Ghafoori—says the following about the new invention:

“The concept proposed in this anchoring system is very promising. We will soon receive the system, and we’ll test it using both static and dynamic loads.”