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

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

Strengthening of R/C beams with high performance concrete jacket

The possibility of strengthening existing RC beams with low thickness high performance jackets is investigated herein. In order to verify the effectiveness of the proposed solution, full scale tests have been performed on 4.5 m long beams. The jackets are made with a high performance fiber reinforced concrete (HPFRC), with an additional 2 mm diameter steel-wire mesh. Two different high performance concrete are investigated: a concrete with a self leveling rheology, that can be cast with reduced thickness, and a thixotropic material that can be placed without moulds. A beam without HPFRC jacket has been used as reference specimen and a second beam have been strengthened with a 40 mm thickness jacket: the self-leveling material was used on the bottom surface whereas the thixotropic material was placed on the lateral surfaces. The experimental behaviour of the reinforced beams has been simulated by means of numerical FE analysis with a commercial program (DIANA). The comparison of the results clarifies the effect of a HPFRC layers on existing beam and the mechanisms governing the flexural response