Cyclic behavior of RC beam-column joints strengthened with FRP systems Roberto Realfonzo a , Annalisa Napoli a,⇑ , Joaquín Guillermo Ruiz Pinilla b a Department of Civil Engineering, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano (SA), Italy b ICITECH, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain highlights  Results of cyclic tests carried out on full scale RC beam-column joints strengthened with FRP are discussed.  Specimens were designed to be representative of existing exterior beam-column subassemblies with inadequate seismic details.  Results have allowed drawing some criticisms related to the design of the joint upgrading.  The most suitable FRP strengthening configurations are identified.  Tests on repaired joints have confirmed the efficiency of the selected strengthening solutions. article info Article history: Received 13 August 2013 Received in revised form 28 November 2013 Accepted 16 December 2013 Available online 19 January 2014 Keywords: RC beam-column joints Experimental tests Seismic upgrade FRP Strength Ductility abstract This paper presents the results of an experimental campaign performed at the Laboratory of Materials and Structural Testing of the University of Salerno (Italy) with the aim to investigate the seismic perfor- mance of RC beam-column joints strengthened with FRP systems. The complete test matrix includes eight full scale specimens designed to be representative of existing exterior beam-column subassemblies with inadequate seismic details. Of these, six were strengthened by using different FRP systems while the remaining ones were used as benchmarks. Once damaged, some specimens were repaired with FRP systems and re-tested. Tests were performed in displacement control by subjecting the specimens to cyclic excitation, whereas the axial load on the column was kept constant and equal to about 300 kN. Test results have provided useful information on the adopted strengthening systems in terms of strength, ductility and energy dissipation capacity. In particular, the results have allowed drawing some criticisms related to the design of the joint upgrading; the most suitable FRP configurations are also iden- tified. Tests on repaired joints have confirmed the efficiency of the selected strengthening solutions. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, repairing and seismic upgrading of under designed reinforced concrete (RC) structures represents a key issue in the ci- vil engineering field. Typically, beam-column assemblages of existing framed build- ings were designed to behave in a weak column-strong beam fash- ion that, under seismic loads, may lead to the formation of local hinges in the column. The associated failure mode represents, therefore, the lower bound of the hierarchy of strength and is char- acterized by a brittle structural failure. A number of technical solutions based on the local strengthen- ing of columns have been proposed in the literature with the aim to improve the seismic performance of such deficient RC struc- tures. However, in gravity load-designed structures where beams are often stronger than columns, increasing the strength and, mainly, the ductility of columns is generally not sufficient by itself since the joint panel becomes the next weakest element due to either lack of transverse reinforcement, discontinuous beam bot- tom reinforcement, or other non-ductile detailing. This condition is mainly found in the case of corner joints or those belonging to façade frames because only partially confined for the absence of beams on the four joint faces; such joints exhibit a progressive deterioration under seismic excitation with the consequent reduc- tion of their strength and stiffness [1]. The brittle failure of joints significantly reduces the overall duc- tility of structures and, in some cases, may lead them to the col- lapse. Therefore, the joint panels should be strengthened by increasing their shear capacity and by improving the effective confinement. 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.12.043 ⇑ Corresponding author. Tel.: +39 089 964085; fax: +39 089 968739. E-mail address: annapoli@unisa.it (A. Napoli). Construction and Building Materials 54 (2014) 282–297 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat