Experimental study on the seismic design and retrofit of bridge columns including axial load effects

ABSTRACT

This research is concerned with validation of alternative theories for seismic design and retrofit of bridge structures. The intent of these methodologies is to not only maintain life safety of bridges in a strong eartquake, but also to control damage while accommodating large seismically-induced deformations in order to maintain post-earthquake serviceability. The primary purpose of this research endeavor is to verify that both Control and Repairability of Damage (CARD) and Retrofit, Control and Repairability of Damage (ReCARD) sacrificial fuse-bar plastic hinge details have adequate fatigue life under realistic seismic loading -including the effects of variable axial loads that arise from a combination of the framing action of multiple column pier bents and vertical ground motion. As a secondary purpose, a new technique called Quasi-Earthquake Displacement (QED) Experimentation is developed to verify the CARD and RECARD construction details. The experimentation is developed to verify the CARD and ReCARD construction details. The experimental technique uses a non-linear time-history computational simulation to predict seismic displacements (and forces) in a prototype structure. These earthquake-induced actions are scaled to permit laboratory experiments to be conducted on reduced scale subassemblages of the prototype structure. It is concluded that reinforced concrete bridge columns that possess sacrificial/replaceable fuse-bars have sufficient cyclic capacity under the most adverse seismic loading conditions (including large axial load variation) to sustain a strong foreshock, mainshock and aftershock