Abstract
In recent years, old reinforced concrete (RC) buildings have increasingly been protected as historic symbols in Italy. The conversion of these buildings can resolve the increasing need for new structures, reducing much social, economic, and environmental impact. Retrofitting solutions by carbon fiber reinforced polymer (CFRP) reinforcements are very common nowadays. Code predictions present uncertainties due to the brittle behavior and the debonding of CFRP strips resulting from concrete cracking. Therefore, especially in the case of old beams, experimental validation is necessary. This paper deals the experimental evaluation of the shear strength of two beams extracted from an old RC building in Rome built in 1929 with modest-quality concrete. Preliminary tests were carried out to evaluate the beam elastic response and the material characteristics. These beams were tested until failure (three-point load shear/bending tests) after strengthening for shear by CFRP U-jacketing and for bending by new steel rebars. The results obtained, together with the extensive data taken from the literature, were compared with the predictions by design code equations. The influence of construction details on beam shear strength and the experimental maximum CFRP strain were also analyzed. Code predictions can be effective to estimate the shear strength of the retrofitted beams.
Highlights
In seismic countries as Italy, many reinforced concrete (RC) buildings were built from the beginning of the 20th century
This paper focuses on the study of retrofitting solutions to improve the load-carrying capacity of existing old RC beams by Externally Bonded Fiber-Reinforced Polymer (EB-FRP) reinforcement much used in construction
The present paper investigates the shear strength of two “real” retrofitted beams extracted by an old RC structure built with poor-quality concrete in Rome in 1929
Summary
In seismic countries as Italy, many reinforced concrete (RC) buildings were built from the beginning of the 20th century. The code equation results are able to estimate the shear strength of the “real” retrofitted beams but the uncertainties due to the brittle behavior of CFRP and to the premature debonding of strips resulting from concrete cracking should be closely considered by the designer. Both beams failed in shear because of improper design of the construction details (insufficient new longitudinal rebar anchorage) resulting in a complete debonding of the CFRP strips that reduced the beam strength. This uncertainty about the compressive strength should be closely considered by a designer to define properly the beam capacity [60,61]
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