• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.87-98
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• 2009

It is well known that reinforcement details in the plastic hinge region of bridge piers give the most important effects on the seismic performance of bridges, from investigations of bridge failures in many earthquake events and in laboratory tests. Longitudinal reinforcement details give larger effects than lateral reinforcement details do. The lap-spliced longitudinal steel shows slip during earthquake events, which results in low ductility and inadequate seismic performance. However, before the issue of the earthquake design code, a considerable number of bridge piers were constructed with lap-spliced longitudinal steel in the plastic hinge region. Therefore, a large amount of research has been conducted on the seismic performance and retrofit of circular and rectangular shaped bridge columns with lap-spliced longitudinal steel. However, research on wall type piers is very limited. This paper investigates the seismic performance of a pier wall by a quasi-static test in the weak axis direction and proposes a retrofit method. From the test with variables being the longitudinal steel detail and the transverse steel amount, it is shown that the currently used definition of yield displacement is not adequate. Therefore a new definition of yield displacement for the ductility investigation for a pier wall is proposed. In addition, a retrofit method by steel plates and bolts is proposed to improve ductility, and test results show that slip of the longitudinal steel is prevented by up to a considerably large displacement.

• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.247-255
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• 2004

An experimental program was undertaken to develop seismic retrofit methods of existing steel moment connections with floor slab for improved seismic performance. Five full-scale composite specimens were tested under cyclic loading. Conventional through-diaphragm connections [please check this; no search results were found for through-diaphragm connections] composed of square-tube column and H-beam were retrofitted by adding either a bottom-flange dogbone (RBS) or an improved welded horizontal stiffener at the beam bottom flange. The effectiveness of the proposed retrofit connections schemes was evaluated. The specimen retrofitted using the RBS concept at the bottom flange showed poor connection ductility. In contrast. specimens with the proposed horizontal stiffener details exhibited improved connection ductility.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.88-97
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• 2012

The objective of this research is to investigate the seismic performance and flexure-shear behavior of square reinforced concrete bridge piers with solid and hollow cross section. Test specimens were nonseismically designed with the aspect ratio 4.5 Two reinforced concrete columns were tested under constant axial load while subjected to lateral load reversals with increasing drift levels. Longitudinal steel ratio was 2.217 percent. The transverse reinforcement ratio As/($s{\cdot}h$), corresponding to 58 percent of the minimum lateral reinforcement required by Korean Bridge Design Specifications for seismic detailing, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. This study are to provide quantitative reference data for the limited ductility design concept and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, collapse, etc. Failure behavior, ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio, residual deformation, effective stiffness, plastic hinge length, strain of reinforcements and nonlinear analysis are investigated and discussed in this paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.53-58
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• 2002

A recent development, a concrete-filled steel(CFS) pier is an alternative to a reinforced concrete bridge pier in an urban area, because of its fast construction and excellent ductility against earthquakes. The capacity of CFS piers has not been used to a practical design, because there is no guide of a seismic design for CFS piers. Therefore, the guide of a seismic design value is derived from tests of CFS piers in order to apply it to a practical seismic design. Steel piers and concrete-filled steel piers are tested with constant axial load using quasi-static cyclic lateral load to check ductile capacity and using the real Kobe ground motion of pseudo-dynamic test to verify seismic performance. The results prove that CFS piers have more satisfactory ductility and strength than steel piers and relatively large hysteretic damping in dynamic behaviors. The seismic performance of steel and CFS piers is quantified on the basis of the test results. These results are evaluated through comparison of both the response modification factor method by elastic response spectrum and the performance-based design method by capacity spectrum and demand spectrum using effective viscous damping. The response modification factor of CFS piers is presented to apply in seismic design on a basis of this evaluation for a seismic performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.6
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• pp.81-90
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• 2011

The purpose of this study was to investigate the seismic performance of reinforced concrete bridge columns with interlocking circular hoops. Three interlocking columns were tested under a constant axial load and a quasistatic, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used for the analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve the existing practice in the design and construction of reinforced concrete bridge columns with interlocking circular hoops.

• Land and Housing Review
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• v.1 no.1
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• pp.43-50
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• 2010

In this study, the influences of steel dampers on the behavior of RC frames were investigated using the experimental approach to suggest the installation methods of steel dampers using K-barces. The performances of RC frames with dampers can be evaluated by superposition the load-displacement curves of RC frames and steel dampers with regard to the influences of K-braces. Three specimens are tested to investigate the cyclic behavior of RC frames with dampers. The performances of RC frames with dampers with respect to strength, rigidity, and hysteretic performance are examined. It was found that test results demonstrates the effect of seismic retrofit on RC frames with steel dampers(D-RCF-KBSF, D-RCF-KBSP) compared with RC frames(N-RCF). An approximate design curves may not be good agreement with those of the tests, it is conservative enough so that you can design of RC frames with steel damper with regard to the influences of K-braces.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.41-54
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• 1999

Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers, circular hollow columns are widely used in Korean highway bridges. Since the occurrence of 1995 Kobe earthquake, there have been much concerns about seismic design for various infrastructures, inclusive of bridge structures. It is, however, understood that there are not much research works for nonlinear behavior of circular hollow columns subjected to eqrthquake motions. The objective of this experimental research is to investigate nonlinear behavior of circular hollow reinforced concrete bridge piers under the quasi-static cyclic load, and then to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. Particularly for this test, constant 10 cyclic loads have been repeatedly actuated to investigate the magnitude of strength degradation for the displacement ductility factor. Important test parameters are seismic design, confinement steel ratio, axial force and load pattern. It is observed from quasi-static tests for 7 bridge piers that the seismically designed columns and the retrofitted columns show better performance than the nonseismically designed colums, i.e. about 20% higher for energy dissipation capacity and about 70% higher for curvatures.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.71-81
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• 2007

For the design of composite bridge piers, detail requirements for the reinforcements is not clear to satisfy the required seismic performance. Composite bridge piers were suggested to reduce the sectional dimensions and to enhance the ductility of the columns under earthquake loadings. In this paper, five specimens of concrete encased composite columns of 400mm diameter with single core steel were fabricated to investigate the seismic performance of the composite columns. Shaking table tests and a Pseudo-Dynamic test were carried out and structural behavior of small-scaled models considering near-fault motions was evaluated. Test parameters were the pace of the transverse reinforcement, lap splice of longitudinal reinforcement and encased steel member sections. The displacement ductility from shaking table tests was lower than that from the pseudo-dynamic test. Limited ductile design and 50% lap splice of longitudinal reinforcement reduced the displacement ductility. Steel ratio showed significant effect on the ultimate strength. Lap splice and low transverse reinforcements reduced the displacement capacity. The energy dissipation capacity of composite columns did not show significant difference according to details.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.729-736
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• 2006

It has been shown that many Reinforced Concrete(RC) structures designed without seismic details have experienced brittle shear failures in the beam-column joint area and resulted in large permanent deformations and structural collapse. In this study, experimental investigations into the performance of exterior reinforced concrete beam-column joints strengthened with the carbon fiber-reinforced polymer(CFRP) under cyclic loading were presented. The CFRP has been applied by choosing different combinations and locations to determine the effective way to improve structural performances of joints. Eight beam-column joints were tested to investigate behaviors of each specimen under cyclic load and to compare performances of seismic retrofit. According to the experimental study, the retrofit strengthened with the CFRP provides significant improvements of flexural capacity and ductility of beam-column joints originally built without seismic details.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.419-428
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• 2013

In this study, experimental research was carried out to evaluate the constructability and seismic performance of high strength R/C exterior beam-column joints regions, with or without the shear reinforcement, using high ductile fiber-reinforced mortar. Five specimens of retrofitted the exterior beam-column joint regions using high ductile fiber-reinforced mortar are constructed and tested for their retrofit performances. Specimens designed by retrofitting the exterior beam-column joint regions (BCJNSP series) of existing reinforced concrete building showed a stable mode of failure and an increased its maximum load-carrying capacity by 1.09~2.03 times in comparison with specimen of BCJNS due to the effect of enhancing dispersion of crack control at the time of initial loading and bridging of fiber from retrofitting new high ductile materials during testing. Specimens of BCJNSP series attained its maximum load carrying capacity by 0.92~0.96 times and increased its energy dissipation capacity by 1.62 times when compared to standard specimen of BCJC with a displacement ductility of 4.