Shear strengthening of reinforced concrete beam with high-performance fiber-reinforced cementitious composite jacketing

The possibility of using thin high-performance jackets aimed at improving the structural and shear capacity of existing reinforced concrete members is investigated in this paper. The jackets are made of high-performance fiber-reinforced concrete, with a steel mesh fabric sometimes added (diameter of the wires = 2 mm [0.078 in.]; wire spacing = 25.4 mm [1 in.]; and ultimate strength of steel = 550 N/mm2 [79.8 ksi]). Two different high-performance cementitious composites are investigated: a self-leveling concrete suitable for casting thin members, and a thixotropic concrete requiring no molds during casting operations. To assess the effectiveness of the proposed solutions, different jackets were used to reinforce short, simply supported reinforced concrete beams (2.85 m [9.35 ft] long) lacking stirrups. The beams were tested up to failure in four-point bending, and the numerous test results, including a close comparison with the reference un-strengthened beam, are presented and discussed. The experimental results demonstrate the effectiveness of the technique proposed. All strengthened beams reached their theoretical bending capacity, whereas the unreinforced beam failed in shear

Strengthening of R/C beams with high-performance Jackets

The possibility of strengthening RC elements for increasing the bearing capacity is an important issue in the retrofitting field. In RC existing structures, made in the ’60s and ’70s, bending and shear reinforcements are often not sufficient to satisfy the prescription of current codes. Hence, in the retrofitting of these structures it is often necessary to increase their bearing capacity. A possible use of low thickness high performance jackets for flexure and shear strengthening purposes is analyzed herein. The jackets are made with a high performance fiber reinforced concrete, with or without an additional 2 mm diameter steel-wire mesh. Two different high performance concrete are investigated: a concrete with a self levelling rheology, that can be cast with reduced thickness, and a thixotropic material that can be placed without moulds. In order to verify the effectiveness of the proposed solution, different jackets were used for reinforcing two different type of beams: a 2.85 m long beams, without stirrups, for shear strengthening and 4.55 m beams, with a low reinforcement percentage, for bending strengthening. The elements were tested up to failure and the comparison between the obtained results is presented herein

Strengthening of RC members by means of high performance concrete

The possibility of using High Performance Fiber Reinforced Concrete for strengthening or repairing existing RC structures has been proposed in the last few years. The paper presents an overview of the different possible applications with this kind of technology. In particular, different materials, having different properties in terms of strength and workability, are available in order to optimize the application. In detail, self-leveling materials and thixotropic materials have been used. The use of jackets in High Performance Fiber Reinforced Concrete allows to increasing the bearing capacity, the stiffness and the durability of RC elements. A series of applications are presented and the obtained benefit are discussed

Corroded RC columns repair and strengthening with high performance fiber reinforced concrete jacket

Reinforcement corrosion can induce severe damage in reinforced concrete (RC) columns leading to a relevant loss of bearing capacity. This condition can be even more critical in case of seismic events. The possibility of repairing and strengthening corrosion damaged columns with high performance fiber RC (HPFRC) jacketing is investigated herein. The main aim of the retrofit intervention is, not only to restore the original bearing capacity, but also to increase the column durability. In order to investigate the effectiveness of the proposed technique, full-scale tests on RC columns under cyclic loads have been performed. Two columns were artificially corroded and one of them was repaired with a HPFRC jacket. The obtained results are compared with those measured on a third un-corroded RC column

Rinforzo a taglio di travi in c.a. mediante incamiciature in calcestruzzo ad elevate prestazioni

La possibilità di rinforzare elementi in C.A. per incrementare la resistenza ultima a taglio mediante l’utilizzo di sottili camicie di calcestruzzi fibroirnforzati ad elevate prestazioni è stata studiata mediante prove sperimentali su travi in scala reale. Nelle strutture in C.A., realizzate negli anni ’60-’70, spesso l’armatura a taglio non è sufficiente per soddisfare i requisisti richiesti dalla corrente normativa e esse devono essere oggetto di adeguamento alle nuove disposizioni. Pertanto nel rinforzo di queste strutture è spesso necessario prevedere un incremento della resistenza a taglio. L’efficacia della tecnica di rinforzo è stata studiata attraverso prove in scala reale su travi di lunghezza pari a 3 m. Le camicie di rinforzo in calcestruzzo fibrorinforzato sono state realizzate con differenti spessori (dai 30 mm ai 50 mm) e mediante l’aggiunta di una rete in acciaio con diametro del filo pari a 2 mm.. Una trave con le stesse caratteristiche ma senza camicia di rinforzo è stata utilizzata come campione di riferimento. I risultati ottenuti, che vengono qui presentati, mostrano l’efficacia della tecnica proposta