Experimental study on the seismic performance of self-centering bridge piers incorporating ECC and superelastic SMA bars in the plastic hinge regions

The seismic performance of pier columns is important to the safety of bridge structures. To improve the deformation capacity and energy dissipation, reduce the residual deformation and plastic damage, and resume normal functions with no or minimal repair after an earthquake, an innovative pier column with self-centering capability based on shape memory alloy (SMA) and engineered cementitious composites (ECC) was proposed. In the plastic hinge region of the pier column, SMA bars and ECC were used to replace the ordinary longitudinal reinforcements and concrete. The superelasticity of SMA can be used to achieve the self-centering function of the pier column; the strain hardening characteristic of ECC can improve the energy dissipation capacity of the pier column and reduce damage. Five specimens were produced, i.e., ordinary reinforced concrete bridge pier (R/C-BP), reinforced ECC bridge pier (R/ECC-BP), steel strand reinforced concrete bridge pier (SS/C-BP), steel strand reinforced ECC bridge pier (SS/ECC-BP) and SMA bar ECC bridge pier (SMA/ECC-BP). After low cycle repeated loading tests, the seismic performances of different piers, such as failure mode, bearing capacity, ductility and energy dissipation capacity, were compared and analyzed. The test results show that SMA material can significantly improve the deformation ability and ductility of the structure and reduce the residual deformation of the structure; ECC material can effectively improve the ductility and energy dissipation capacity of the structure and reduce the speed of cracking. Compared with ordinary reinforced concrete specimens, SMA/ECC pier columns were less damaged with better ductility and self-centering effects and exhibited excellent seismic performance.