Abstract:
Bridge piers are the primary lateral force-resisting system of a bridge that experiences inelastic deformation during an earthquake. The integration of Shape Memory Alloy (SMA) into steel bridge piers presents a promising solution to significantly mitigate seismic damage, owing to the self-centering capabilities of SMA. Three-dimensional (3D) finite element (FE) models are developed to simulate the cyclic response of steel piers. These FE models, validated using test data, form the basis for developing models featuring super-elastic SMA in the buckling wavelength region of the steel bridge pier. This study investigates various response parameters including strength, ductility, axial shortening, residual drift, cumulative energy dissipation, and relative self-centering efficiency under uni-directional loading. Results indicate that SMA-01 (FeMnAlNi-Based, E=98.5 GPa) induced column yields similar load capacity and ductility as conventional steel columns, while SMA-03 (FeMnAlNi-Based, E= 46.9 GPa) induced column exhibits a 20% decrease in load capacity but improved ductility. SMA incorporation significantly reduces axial shortening and residual drift, with SMA-03 (FeMnAlNi-Based, E= 46.9 GPa) leading by 650%, respectively, compared to conventional steel columns at 4% drift. Notably, SMA-Steel hybrid columns maintain <1% residual drift up to 4% drift ratios and exhibit a high relative self-centering efficiency (RES) of 0.8 to 1, surpassing conventional steel columns. Moreover, they demonstrate a substantial reduction of around 60-70% in cumulative energy dissipation.
Following the comparative study of steel and SMA-steel hybrid columns under cyclic loading, a comprehensive parametric study is conducted to analyze the impact of different key design parameters on the strength, ductility, and residual drift of these hybrid piers. These parameters include types of SMA, heights of the incorporation of SMA tube, axial load, diameter-to-thickness ratio, and height-to-diameter ratio. The study outcomes reveal that different SMAs have different effects on the strength, ductility, and residual drift based on their material properties. While some are good for strength and ductility, some are for residual drift. In most cases, increasing the diameter-to-thickness and height-to-diameter ratios in hybrid columns decreases the load capacity and ductility and increases the residual drift. Furthermore, employing SMA tubes past the buckling wavelength region does not significantly improve the load carrying capacity and ductility. However, a substantial enhancement in self-centering capacity is observed by employing SMA tubes past the buckling wavelength region. The hybrid columns exhibit almost identical load carrying capacity and ductility for different axial loads. These findings provide valuable insights into the performance and optimization of hybrid steel bridge piers utilizing Shape Memory Alloys, with potential practical applications in the field of civil engineering.