Precast fiber reinforced cementitious composites for seismic retrofit of deficient rc joints – A pilot study

The objective of this study was to investigate the seismic behavior of deficient reinforced concrete exterior beam–column joints constructed with low-strength concrete and plain reinforcing bars before and after retrofitting with prefabricated HPFRCC (high-performance fiber-reinforced cementitious composite) panels. For this purpose, four full-scale beam–column–slab–transverse beam sub-assemblies were tested under constant column axial load and reversed static cyclic lateral loads. Before these full-scale tests, four simple panel specimens, which were built to represent the joint cores, were also tested under diagonal tension before and after retrofitting with prefabricated HPFRCC panels. Both types of tests showed that retrofitting with prefabricated HPFRCC panels provided considerable enhancement, both in strength and in displacement capacity, provided that the panels were properly anchored to the joint core and the slippage of the beam longitudinal bars in the joint core was prevented. In the analytical part of the study, the strengths of the reference and retrofitted panels, tested under diagonal tension, were predicted quite accurately using non-linear finite element analysis. Furthermore, Mohr’s circle and strut-and-tie modeling was used to obtain the complete load–displacement relationships of the reference and retrofitted joint sub-assemblies.