alberto.meda@uniroma2.it
serena.mostosi@unibg.it
paolo.riva@unibg.it
La possibilità di rinforzare elementi in C.A. per incrementare la resistenza ultima a taglio mediante l’utilizzo di sottili camicie di calcestruzzi fibrorinforzati 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 requisiti richiesti dalla corrente normativa ed 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 2.85 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.
The interest for strengthening and repairing R/C structures has increased in the last few years, as most of the existing structures were built according to past codes and do not satisfy some of the provisions of current codes. Furthermore, existing structures are often required to sustain greater variable loads than in the past, thus requiring an increase of their bearing capacity. As most of the existing structures are very likely to be under-reinforced or lightly-reinforced, something that is typical of the design approach of the sixties and seventies of the last century. In this research, the attention has been devoted to the effects of high performance jackets with reduced thickness on the increase of the carrying capacity under shear actions of R/C members.
The effectiveness of using HPFRC has been assessed in this project by means of an experimental campaign on beams having span of 2.50 m and sections and 450 x 200 mm,lacking stirrups. The use of two kinds of high performance fiber reinforced concrete has been considered: a material having an almost self levelling rheology, able to cast very thin jackets, and a newly developed thixotropic material which can be easily used to create the jacket. The strengthening HPFRC jackets were cast after sandblasting of the existing concrete surface and, due to the high bond properties of the material, it was not necessary to apply any primer in order to ensure a perfect adhesion of the jacket to the original concrete. The use of high performance fiber reinforced concrete jackets combined with high performance steel mesh has also been investigated.
The beams were tested up to failure in 4-point bending, and the numerous test results, including a close comparison with the reference unstrengthened beam, are presented and discussed.
Do you have an account or a subscription?
Sign in