Ductility of high-performance concrete and very-high-performance concrete elements with Ni-Ti reinforcements

This article presents an experimental study on the behavior of high performance concrete (HPC) and very high performance concrete (VHPC) concrete columns with Nickel-Titanium (Ni-Ti) shape memory alloy (SMA) reinforcements in critical regions subjected to constant axial and lateral cyclic load combinations. These materials make the cast-in-place of concrete easier by reducing the amount of transverse reinforcement, improving performance, attenuating damage in critical regions, minimizing residual deformations and reducing repair costs in structures located in seismic areas. Seven experimental tests were carried out to analyze the behavior of this element type. A nonlinear static cyclic pushover analysis was performed with finite element software (OpenSees), whose results were compared with the experimental results. This analysis allowed a parametric analysis to be run to extrapolate the experimental results. Strength capacity was approximately 41.8% greater in absolute terms in the specimens manufactured with VHPC and 6.2% greater in adimensional terms in those manufactured with HPC. Displacement ductility was 34.0% higher in the HPC specimens, and lowered with relative normal force and with transverse reinforcement separation. A residual drift ratio below 0.70% was generally observed when specimens reached 20% strength capacity loss. The residual drift ratio increased as a result of progressive concrete cover degradation, especially in the specimens manufactured with HPC.