Experimental assessment of unreinforced exterior beam–column joints with deformed bars

In the performance assessment of typical existing buildings, seismic collapse safety might be significantly affected by non-linear behavior of joints that are involved in the failure mechanism, especially if they are characterized by poor structural detailing such as the lack of an adequate transverse reinforcement in the joint panel. Unfortunately, commonly accepted tools to assess existing joints capacity are not available. Few reliable approaches for modeling all sources of nonlinearity are proposed in literature for poorly designed beam–column joints because of relatively poor information from experimental tests. The present study aims at improving the understanding of seismic performance of exterior joints without transverse reinforcement in existing \RC\ buildings through experimental tests. Two full-scale exterior unreinforced beam–column joint sub-assemblages are tested under cyclic loading. The specimens are reinforced with deformed bars but they are different for beam longitudinal reinforcement ratio. Two different kinds of joint failure are expected, with or without the yielding of the adjacent beam. Strain gauges located on beam bars and displacement transducers on the joint panel allow the complete definition of both the main deformability contributions, namely fixed-end-rotation and shear strain of joint panel, highlighting the differences between failure modes. Design criteria, adopted setup and experimental results are described and discussed. Finally, experimental results are compared with proposals from literature in terms of shear strength.