Cyclic Loading Test and Numerical Modeling on Prefabricated UHPC Tube-Confined Rectangular Bridge Piers with Different Base Connections

Reinforced concrete (RC) bridge piers, one of the most widely used pier types, are vulnerable to damage during an earthquake and may not have sufficient durability against the harsh environment. To tackle these problems, a prefabricated UHPC tube, as the permanent formwork, was proposed to replace the cover concrete of the RC piers in enhancing the seismic performance of RC bridge piers. In this study, cyclic loading tests and numerical analyses were conducted to evaluate the efficiency of the UHPC tube. Three specimens, including one reference RC column and two prefabricated UHPC tube-confined (PUTC) columns, were fabricated and tested under quasi-static cyclic load. For specimen PUTC1, the prefabricated tube is disconnected from the footing at the column base. To utilize the tensile strength of UHPC (greater than 6 MPa), the tube is embedded into the footing in specimen PUTC2. The numerical study is performed to further examine the effects of six design parameters on the cyclic responses of the PUTC columns. The results demonstrated that the use of the UHPC tube can significantly enhance the seismic performance of the RC columns and reduce their seismic damage. The tube-to-footing connection noticeably affects the cyclic behavior of the PUTC columns. Due to the contribution of the UHPC tensile strength, embedding the UHPC tube into the footing can reduce the measured strain of the longitudinal reinforcements inside the footing. The embedded connection improves the maximum lateral force and displacement ductility by 26.0 and 8.3%, respectively, compared with the pier with the unembedded UHPC tube. The PUTC column with embedded UHPC tube exhibits less residual deformation because of the bridging effect of the steel fibers and confinement effect of the tube. When the UHPC tube is properly designed, it can be used to fully substitute transverse reinforcements and partially substitute longitudinal reinforcements in the PUTC columns.