• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.17-24
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• 2005

Response of reinforced concrete (RC) column-bent piers subjected to bidirectional seismic loadings was experimentally investigated. RC column-bent piers represent one of the most popular shapes of piers used in Korea highway bridges. Four column-bent piers were constructed in 400 mm diameter and 2,000 mm height. Each pier has two circular supporting columns. These piers were tested under bidirectional lateral load reversals with an axial load of $0.1f_{ck}A_g$. The test parameters included : different transverse reinforcement contents and lap-spliced longitudinal reinforcing steels. Test results indicate that the lap splice of longitudinal reinforcing steels have significantly influenced on hysteretic response of column-bent piers similar to previous test results for single columns with corresponding test parameters. Column capacity was changed with the level of transverse confinement. From the comparison of test result for single column under unidirectional loading, the damage of single column was concentrated on lower plastic hinge region but the damage of column-bent piers was scattered to upper and lower plastic hinge region.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.697-707
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• 2004

Most bridge piers were practically designed and constructed with lap spliced longitudinal reinforcing steels before the 1992 seismic design provisions of Korea Bridge Design Specification were implemented. It has been known that lap splice of longitudinal reinforcement in the plastic hinge region is not desirable for seismic performance of RC bridge piers. The objective of this research is to evaluate the seismic performance of existing circular reinforced concrete bridge piers by the Quasi-static test and to propose the need of seismic retrofit of existing bridge piers through the damage level. Test specimens were nonseismically designed with the aspect ratio 4.0 which could induce the flexural failure mode. It was confirmed from this experiment that significant reduction of seismic performance was observed for test specimens with lap spliced longitudinal reinforcing steels. Pertinent seismic retrofit was determined to be needed for existing RC bridge piers with the lap-spliced of $50\%$ longitudinal reinforcing steels.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.121-128
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• 2005

A RC column-bent pier represents one of the most popular piers used in highway bridges. Seismic performance of reinforced concrete (RC) column-bent piers under bidirectional seismic loadings was experimentally investigated. Six column bent-piers were constructed with two circular supporting columns which were made in 400 mm diameter and 2,000 mm height. One single column specimen was additionally made to comparatively evaluate the seismic response of RC column-bent piers. Test parameters are different transverse reinforcement and loading pattern. These piers were tested under lateral load reversals with the axial load of $0.1 f_{ck}A_g$. Three specimens were subjected to bidirectional lateral load cycles which consisted of two main longitudinal loads and two sub transverse loads in one load cycle. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter three specimens were generally bigger than those of the former three specimens. Plastic hinges were formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom plastic hinge of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• 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.