Experimental and numerical investigations on the lateral response of post-tensioned base rocking steel bridge piers

This doctoral dissertation is aimed at contributing to the further development of the rocking isolation concept and posttensioning technology in bridges by proposing an unbounded post-tensioned (PT) steel pier. The proposed pier consists of a circular steel tube, circular end plates, prestressed tendon(s), and supplemental energy dissipation devices, and is configured to rock at its interface with the foundation. The main characteristic of such a pier is its ability to ensure small residual drifts after undergoing inelastic deformations during cyclic loading. The system has a tendency to close the gap due to the presence of superstructure dead load and tendon prestressing force. An experimental program was designed that included a series of quasi-static cyclic tests on 1/3-scale specimens with the objective of investigating the effects of column diameter-to-thickness ratio, base plate, and energy dissipaters and their locations on the lateral cyclic response. A component testing program was also conducted to characterize the cyclic loss of post-tension force due to wedge seating in a typical monostrand anchorage system. Using the experimental data, the calibration of the finite element (FE) procedure was done at material, component, and global system levels. The FE models were leveraged to conduct a comprehensive parametric study with the purpose of developing design criteria to minimize residual pier drifts after sustaining cyclic inelastic deformations. Using nonlinear time history FE analyses, the seismic response of a bridge incorporating such a pier was examined to evaluate the effects of different design parameters. The cyclic behaviour of buckling-restrained energy dissipating steel bars was studied. Extensive experimental and FE investigations on the cyclic behaviour of such energy dissipation devices were conducted. The results of the investigations demonstrate that a PT base rocking steel pier could exhibit a stable and robust self-centering response under severe quasi-static cyclic loading, with minimal damage to the column and most of the hysteretic energy confined within the replaceable elements. The results of dynamic FE studies show that a bridge utilizing such a pier has the potential to undergo consecutive earthquakes without sustaining significant damage and return to its original position without requiring abutment component stiffness and strength.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat