Behaviour of retrofited precast UHPC and Ni-Ti SMA column-to-foundation connection with CFRP wrapping layers

Four precast column-to-foundation connection specimens, previously tested under lateral reversed cyclic loading and constant axial load (first-stage tests), were repaired with Carbon Fibre Reinforced Polymer (CFRP) layers in the areas where plastic hinges had formed retested same loads (second-stage tests). The columns originally manufactured ultrahigh-performance concrete (UHPC) high stee-fibre content (volumetric steel/fibre ratio 1.9%). steel bars replaced superelastic Ni-Ti SMA that crossed column/foundation interface. Two types of between column foundation analysed: protruding smooth pocket (SP). specimens subjected to level relative both first second-stage tests. objective was determine whether initial performance UHPC reinforced connections against can be restored after a seismic event by means simple economic retrofitting. effectiveness number strengthening CFRP also studied (two or three wrapping layers) for each type. main results PB SP respect original respectively: an average strength capacity loss 8% 19%, displacement ductility increase 42%, dissipated energy 48% 53% higher stiffness 9.5% 21% lower. No significant differences observed repairs done two layers.