CURVATURE VARIATION OF EARTHQUAKE-EXPERIENCED RCBRIDGE PIER IN THE PLASTIC HINGE REGION

摘要

Reinforced concrete (RC) bridge structures may be expected respond inelastically in a design-levelearthquake. Damage is expected in regions that experience inelastic action, with the degree of damagedepending on the earthquake characteristics as well as the column design. Before the implementation ofthe 1992 seismic design provisions in Korea, longitudinal steels of RC bridge piers were practically lapsplicedin the plastic hinge region. Experimental investigation was made to evaluate the seismicperformance of RC bridge pier specimens in a flexure/shear failure mode. The objective of this study is toincur and assess the damage of RC bridge pier specimens under the artificial earthquake motions with thespecified PGA, to evaluate the displacement and curvature ductility of earthquake-experienced RC bridgepiers with lap-spliced longitudinal reinforcement in the plastic hinge region, and to investigate the effect ofthe fiber reinforced plastic (FRP) wrap for the seismic enhancement.Seven (7) circular test specimens in an aspect ratio of 2.5 were made with three test parameters:confinement ratio, lap splice, and retrofit FRP material. They were damaged under series of artificialearthquakes with the PGA, being compatible in Korean peninsula by the pseudo-dynamic test. Directlyafter the pseudo-dynamic test, damaged test columns were laterally actuated under repeated cyclic loadingssimultaneously under a constant axial load. Through the displacement and curvature measurements,residual seismic performance was evaluated for damaged test specimens. The relationship between thecurvature and the displacement ductility was investigated and compared with previous models by JRA [5],Priestley [14], and Son [16]. Test results show that lap-spliced RC pier specimens were strongly requiredof timely retrofit against the probable earthquakes, and the FRP wrapped columns showed significantenhancement of seismic capacity even if lap splice of 50% longitudinal reinforcement. New empiricalformula for the plastic hinge length was proposed considering the effect of transverse confinement.