ABSTRACT
ABSTRACT: Recent experiments in the US, Japan and China have shown that replacement of transverse steel reinforcement in a reinforced concrete (RC) bridge column with an external fiber reinforced polymer (FRP) tube can significantly enhance ductility and energy dissipation capacity of the column. This paper reports on a comparative analytical study to examine the effect of column encasement in FRP tube on its seismic performance at the sectional, member, and system levels. A multi-span bridge in the State of Washington was chosen for this comparison. A non-linear finite element model of the bridge was assembled with and without FRP tube. Since FRP has a lower rupture strain than steel spiral, and because of its linear elastic response to failure, the tube-encased column section shows less ductility but higher strength than its RC counterpart. On the other hand, at the member level, the tube-encased column distinctly outperforms its RC counterpart with almost twice the base shear and over three times the lateral drift. This phenomenon was attributed to the effective role of FRP tube in extending the plastic hinge zone of the column well beyond its typical range in conventional RC columns. The earthquake spectrum analysis indicates that the bridge with tube-encased RC columns is capable of withstanding a major earthquake with 2500-year return period, while the conventional bridge suffers irreparable damage. A seismic simulation of the entire bridge under a major historical earthquake confirms these findings.
