Experimental tests of unreinforced exterior beam–column joints with plain bars

• Two experimental tests on joints without transverse reinforcement with longitudinal hook-ended plain bars are presented.
• Two different kinds of joint failure mode are expected, with or without the yielding of the adjacent beam.
• Design criteria, adopted setup and experimental results (at global and local level) are described and commented.
• A database as wide as possible for this kind of tests is collected.
• A comparison between joint shear strength models existing in literature or codes and experimental results is carried out.

Reinforced concrete buildings designed according to obsolete seismic codes or for gravity loads only are widespread in Italian and Mediterranean building stock. Past earthquakes showed that, for these buildings, shear failure in beam–column joints can lead to structural collapse mainly due to the inadequate joint confinement. The construction details used in these structural elements are commonly recognized as the likely cause of non-ductile structural failure modes under seismic actions, due to the lack of capacity design principles.A significant amount of research on seismic performance of unreinforced beam–column joints has been carried out in last years, but a very few portion of them handled with specimens unreinforced in the joint region and with plain hook-ended longitudinal bars. A higher number of tests is needed to deeper understand joint seismic response in order to validate the (few) existing models or calibrate new ones.This study aims at improving the understanding of seismic performance of exterior non-conforming joints in existing RC buildings. Two experimental tests on joints without transverse reinforcement are designed and carried out. The specimens are different for beam longitudinal reinforcement ratio and they are both reinforced with plain longitudinal bars. Two different kinds of joint failure are expected, with or without yielding of the adjacent beam. Design criteria, adopted setup and main experimental results are described. Strain gauges located on beam bars and displacement transducers on the joint panel allow the complete definition of both the deformability contributions of fixed-end-rotation and shear strain of joint panel. Finally, a comparison between joint shear strength models existing in literature or codes and experimental results (considering a wider experimental database) is carried out.