Cyclic Testing of Lap-Spliced Columns Retrofitted with UHPC-Cover Replacement

AbstractIt is the purpose of this study to evaluate, through combined experimental and numerical research, the performance of ultra-high-performance concrete (UHPC) jackets as a means of seismic retrofitting of columns with brittle detailing under cyclic loading. A series of conventionally designed RC column elements were constructed based on detailing methodologies of pre-1980s standards. After imparting preliminary damage to the columns, simulating the aftereffects of seismic excitation, the plastic hinge zone was repaired using cover replacement by a commercial-grade tension-hardening UHPC jacket and tested under cyclic displacement reversals to obtain quantified evidence regarding the performance of this retrofit methodology. Significant improvements in strength and ductility were observed in both the UHPC-repaired and -strengthened specimens, while failure modes associated with the limitations of lap-spliced connections at the column–footing interface were eliminated. Parallel finite-element analysis (FEA) simulations were used to evaluate the broader distributions of the longitudinal strains in the flexural reinforcement, illustrating the contribution of the UHPC jackets in prolonging the seismic response of retrofitted members.