Concrete Beams Strengthened with External Prestressing using External Tendons and Near-Surface-Mounted Reinforcement (NSMR)

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Title: Concrete Beams Strengthened with External Prestressing using External Tendons and Near-Surface-Mounted Reinforcement (NSMR)

Author(s): B. Taljsten and H. Nordin

Publication: Special Publication

Volume: 245

Issue:

Appears on pages(s): 143-164

Keywords: CFRP; concrete; epoxy; flexure; near-surface-mounted reinforcement; prestressing; steel; tendons

Date: 4/1/2007

Abstract:
Strengthening of concrete structures with fibre reinforced polymer materials has today grown to be a widely used method over most parts of the world. As a way of higher utilization of the FRP (Fibre Reinforced Polymers) prestressing has proved to be beneficial. Most of the research done with prestressing Carbon Fibre Reinforced Polymers (CFRP) for strengthening has been with surface bonded plates. However, in this paper a presentation is given where CFRP quadratic rods are bonded in the concrete cover in sawed grooves and then immediately prestressed. Testing has, proven this to be an advantageous way of bonding CFRP to the concrete. There is also a tendency that the shear forces between the CFRP and the concrete are transferred more efficiently compared to surface bonded plates and sheets. In the tests performed, no mechanical device has been used to keep the prestress during testing, which then means that the adhesive has to transfer all shear stresses to the concrete. These tests have then been compared with concrete beams strengthened with prestressed external steel and CFRP tendons and similar load carrying capacity has been obtained.