• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.1-12
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• 2004

Due to the 1989 Loma Prieta, 1995 Hyogoken Nambu earthquakes, etc, a number of bridge columns  were collapsed in flexure-shear failures as a consequence of the premature termination of the column longitudinal reinforcement. Nevertheless, previous researches for the performance of bridge columns were concentrated on the flexural failure mode. It is well understood that the seismic behaviour of RC bridge piers was dependent on the performance of the plastic hinge of RC bridge piers, the ductility of which was desirable to be computed on the basis of the curvature. Experimental investigation was made to evaluate the variation of the curvature of the plastic hinge  region for the seismic performance of earthquake-damaged RC columns in flexure-shear failure mode. Seven test specimens in the aspect ratio of 2.5 were made with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes that could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading under a constant axial load, $P=0.1f_{ck}A_g$. Residual seismic capacity of damaged specimens was evaluated by analzying the moment-curvature hysteresis and the curvature ductility. Test results show that the biggest curvature was developed around 15cm above the footing, which induced the column failure. It was observed that RC bridge specimens with lap-spliced longitudinal steels appeared to fail at low curvature ductility but significant improvement was made in the curvature ductility of RC specimens with FRP straps wrapped around the plastic hinge region. Based on the experimental variation of the curvature of RC specimens, new equivalent length of the plastic hinge region was proposed by considering the lateral confinement in this study. The analytical and experimental relationship between the displacement and the curvature ductility were compared based on this proposal, which gave excellent result.

• Composites Research
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• v.31 no.2
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• pp.57-62
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• 2018

Interfacial and mechanical properties of neat and two sizing agents coated glass fiber (GF)/polydicyclopentadiene (p-DCPD) composites were evaluated at room and low temperatures, $25^{\circ}C$ and $-20^{\circ}C$. Sizing agents of GFs were extracted using acetone and compared via FT-IR. Surface energy and work of adhesion between GFs and p-DCPD were calculated by dynamic contact angle measurement. Mechanical properties of different GFs were determined using single fiber tensile test and interfacial properties of single GF reinforced DCPD strip were determined using cyclic loading tensile test. Mechanical properties of GFs/p-DCPD composites at room and low temperatures were determined using tensile, compressive, and Izod impact tests. Interfacial and mechanical properties were different with sizing agents of GFs and the optimized condition of sizing agent was found.