Seismic performance of segmental rocking columns connected with NiTi martensitic SMA bars

As well known, the damping or energy dissipation capacity of bridge columns is very important because it is directly related to the design spectrum and affects the seismic performance of whole bridge systems. For this reason, several investigations evaluating the energy dissipation capacity of segmental columns, which has a small energy dissipation capacity itself, have been conducted by adopting various material types of energy dissipating (ED) bars. This paper investigates the damping capacity of post-tensioned (PT) segmental rocking columns connected with large diameter (36.5 mm) martensitic SMA bars at their base as ED bars. Two aspect ratios for the columns are considered: 7.5 for slender and 5.0 for medium size. Moment-curvature relationships and complementary computational tools are adopted to model the behavior of the columns. A bilinear model for the PT tendon and a modified four-spring model for the martensitic SMA bar are used. From the quasistatic cyclic analysis, the martensitic SMA bars leads to an equivalent damping ratio between 10.5% and 12.5% for the different aspect ratios and PT tendon forces. For the sake of comparison, another material type of the SMA bar, which is 25.4 mm diameter superelastic bar, is considered. The damping ratio of the columns with the martensitic SMA bars is much higher than the use of the superelastic SMA bars showing between 5% and 7% damping ratio.