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Strengthening of RC members with near-surface mounted CFRP rods
The near-surface mounted reinforcement (NSM) technique using carbon fibre-reinforced polymer (CFRP) rods is very effective in enhancing the flexural strength of reinforced concrete beams whatever the filling material (resin or mortar) used. In most cases, the strengthening of reinforced concrete (RC) members by CRFP rods leads to a different failure mode than for conventional RC beams. For ordinary RC members, the failure mode from rupture of tensile reinforcement to compressive concrete crushing depends on the ratio between tensile reinforcement and concrete compressive strength. For strengthened RC members, the failure mode from degradation of the CFRP rod mounting to compressive concrete crushing depends on a coupled ratio between CFRP cross-section and CFRP length versus concrete compressive strength. In the case where the failure of strengthened members is due to the NSM system failure, two different types of rupture are possible: If the CFRP rod is longer than the cracked span length of the beam at the ultimate stage, the failure is due to the pull-out of the rods inducing almost simultaneous splitting of the cracked concrete surrounding the groove. If the load causes some cracks which reach the end of the CFRP rod, the failure is due to the peeling-off of the concrete covering the groove from the end of the rod. The type of filling material used can change the failure mode. The bonding between old concrete and filling material could be a weak point. As a result, the beam strengthened by CFRP rods using mortar as filling material exhibits a debonding of the mortar from the groove. Further studies concerning the increase of the bonding between old concrete and mortar (when used as filling material) are needed. An increase in the surface roughness of the groove could be tested. The concrete strength does not influence the load-carrying capacity of the strengthened beam when the failure occurs by NSM system failure. No reduction in the deflection at ultimate load is observed for beams with 300 cm strengthening length. The existing analytical models already used in standard RC beams show a strong correlation with the experimental results in terms of the load-deflection curve. But these models do not predict the ultimate load in the case of non-conventional failure of the beams studied.
Strengthening of RC members with near-surface mounted CFRP rods
The near-surface mounted reinforcement (NSM) technique using carbon fibre-reinforced polymer (CFRP) rods is very effective in enhancing the flexural strength of reinforced concrete beams whatever the filling material (resin or mortar) used. In most cases, the strengthening of reinforced concrete (RC) members by CRFP rods leads to a different failure mode than for conventional RC beams. For ordinary RC members, the failure mode from rupture of tensile reinforcement to compressive concrete crushing depends on the ratio between tensile reinforcement and concrete compressive strength. For strengthened RC members, the failure mode from degradation of the CFRP rod mounting to compressive concrete crushing depends on a coupled ratio between CFRP cross-section and CFRP length versus concrete compressive strength. In the case where the failure of strengthened members is due to the NSM system failure, two different types of rupture are possible: If the CFRP rod is longer than the cracked span length of the beam at the ultimate stage, the failure is due to the pull-out of the rods inducing almost simultaneous splitting of the cracked concrete surrounding the groove. If the load causes some cracks which reach the end of the CFRP rod, the failure is due to the peeling-off of the concrete covering the groove from the end of the rod. The type of filling material used can change the failure mode. The bonding between old concrete and filling material could be a weak point. As a result, the beam strengthened by CFRP rods using mortar as filling material exhibits a debonding of the mortar from the groove. Further studies concerning the increase of the bonding between old concrete and mortar (when used as filling material) are needed. An increase in the surface roughness of the groove could be tested. The concrete strength does not influence the load-carrying capacity of the strengthened beam when the failure occurs by NSM system failure. No reduction in the deflection at ultimate load is observed for beams with 300 cm strengthening length. The existing analytical models already used in standard RC beams show a strong correlation with the experimental results in terms of the load-deflection curve. But these models do not predict the ultimate load in the case of non-conventional failure of the beams studied.
Strengthening of RC members with near-surface mounted CFRP rods
Al-Mahmoud, Firas (author) / Castel, Arnaud (author) / Francois, Raoul (author) / Tourneur, Christian (author)
Composite Structures ; 91 ; 138-147
2009
10 Seiten, 13 Bilder, 3 Tabellen, 19 Quellen
Article (Journal)
English
analytisches Modell , Biegefestigkeit , Bruchlast , Druckspannung , Durchbiegung , Durchbiegungsdiagramm , Festigkeitserhöhung , Füllstoff , kohlenstofffaserverstärkter Kunststoff , Kunstharz , Materialbruch , Mörtel , Rauigkeit , Rille , Rissbildung , Stab , Tragfähigkeit , Versagensart , Verstärkung (Festigkeit)
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