For many years composite plates such as CFRP (Carbon Fiber Reinforced Plastic) have been state of the art for post-flexural strengthening of existing reinforced concrete structures. Thanks to the innovation called CFRP L-shaped plates; it is possible to shear-strengthen reinforced concrete structures.

CFRP Plates

The maintenance, rehabilitation and change in use of existing reinforced concrete, timber and masonry structures has increased in importance as the number of new structures has declined. In addition to steel, the established strengthening material, composites such as Carbon Fiber Reinforced Plastics (CFRP) have been globally accepted and are state-of the art for externally bonded flexural strengthening. This has been mainly due to the research work undertaken by Prof. Urs Meier at EMPA Duebendorf. CFRP plates were first used to strengthen a structure on the Ibach bridge near Lucerne/ Switzerland in 1991.

CFRP plates and fabrics have the advantage of easy handling thanks to their lightweight, corrosion resistance and high strength. Furthermore, they have a longer fatigue life than steel.

Now there is a Swiss innovation in composite fiber materials in the form of externally bonded CFRP L-shaped plates for shear strengthening of reinforced concrete structures. It is possible to prefabricate these plates using a special production technique.

The CFRP L-shaped plates are sold by Sika® .

Large-scale tests

EMPA carried out large-scale 4-point flexural tests to show the feasibility of externally bonded shear strengthening systems using CFRP L-shaped plates and CFRP fabrics. The tests demonstrated the general mechanical behavior of the systems.

Beams strengthened with the flange-anchored L-shaped CFRP plates demonstrated the ductile behavior of the member. At the ultimate load level the plates act theoretically as ties between the anchorage in the flange and the bottom of the web. The test beams strengthened with CFRP fabric showed that inadequate anchorage results in debonding and the member displayed a brittle behavior.

Contact:  Christoph Czaderski