Cyclic response of existing r.c. columns repaired or retrofitted by mean of steel and FRP jacketing technique

Seismic assessment of reinforced concrete structures as well as their rehabilitation and strengthening is dealt with in many experimental and theoretical researches. New trends in seismic assessment essentially refer to “performance based design”. Experimental research both on seismic assessment of existing elements as well as on the efficiency of different retrofitting techniques is essential. Much research is currently being directed towards retrofitting solutions for existing reinforced concrete structures under seismic load. Among these, fibre-reinforced polymer (frp) confinement of elements stressed under axial and/or bending action is an increasingly popular solution, with a similar trend in research effort. Confining concrete can in fact significantly enhance both its resistance and stiffness properties; the exterior frp jacket, besides, protects the inner core from temperature and humidity effects, adding to its durability. This paper focuses on current experimental tests at the Laboratory of experiments on materials and structures of the University of Roma Tre on eight 1:6 scaled column specimens representative of tall and squat 2,500 m diameter circular r.c. piers of regular (14-21-14 m tall) and irregular bridges (14-7-21 m tall) (Fig. 1) designed according to EC8 [1] and Italian Code [2]. In previous research [3, 4] some columns were tested until collapse by pseudodynamic tests but others are still entire. An accurate study to detect the level of degradation in materials, as the case of real structures after an earthquake, is now performed. Then, based on the evaluation done, EC8 columns are repaired and the Italian ones retrofitted by mean of FRP jacket with the aim of enhancing ductility and shear capacity. Actual tests aim to evaluate the effectiveness of this tecnique. Test equipment, planned tests and results of elastic tests performed to evaluate test equipment and preliminary numerical analysis results are presented