• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.547-552
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• 1998

Lateral pressure by circular reinforcement greatly enhances the maximum strength and ductility of spiral columns. The lateral confinement effects will be improves ductility of high-strength concrete. The major purpose of this paper is to study on the improvements of maximum strength and strain at that point of spiral concrete columns subject to axial loads. For this purpose, this study collected the other analytical results and the experimental data that has been performed by a lot of worldwide researchers and also analyzed it statistically. As the result, the theoretical equation for predict maximum strength and strain at that point was proposed. It is based on calculation of lateral confinement pressure generated by circular reinforcement, and the resulting improvements in strength and ductility of confined concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.145-150
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• 2001

With the increase in the use of High-Strength Concrete(HSC) despite the its weakness like brittle characteristic, it is important to improve the performance of HSC columns, nowadays. Therefore, it is common to use higher strength steel in HSC for the purpose of ductility and strength improvement. This experimental study was set up to investigate the inelastic behavior of HSC(700kg/$cm^{2}$) columns subjected to combined axial and repeated lateral loads. Effects of key variables such as the volumetric ratio of transverse reinforcement, tie configuration and tie yield strength are studied in this research program. Test results indicate that inelastic response of HSC columns improve with proper confinement of core concrete. Increasing the amount of transverse reiuorement results in increased ductility.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.879-884
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• 2002

The objective of this study is to investigate the seismic capacity of the non-seismically detailed RC bridge piers before and after applying a seismic retrofitting method using stainless steel wire mesh. Total nine circular section RC piers were constructed. Different lap splice longitudinal reinforcement details were adapted for four specimens and various types of stainless steel wire mesh were applied for the remaining five specimens. Harmonic cyclic lateral load was applied on each specimen under a constant axial load. The test results indicated that the existing circular piers have low seismic capacity while the stainless steel wire mesh retrofitting method improves the seismic capacity considerably. In addition, test results revealed that the circular section piers could have a considerable amount of ductility if longitudinal bars are not lap-spliced in potential plastic hinge zone. Based on this experimental study it could be concluded that the seismic performance, that is ductility and energy absorption capacity, of the non-seismically detailed RC bridge piers would be increased by applying the stainless steel wire mesh seismic retrofitting method.

• Journal of the Korea Concrete Institute
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• v.11 no.5
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• pp.107-118
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• 1999

10 RC bridge piers have been made on a 1/3.4 scale model, and six piers of them were retrofitted with glassfiber. The have been tested in the quasi-static cyclic load so as to investigate their seismic enhancement before and after retrofitting with glassfibers. The objective of this experimental study is to investigate how to strength the ductility of reinforced concrete bridge piers which have been nonseismically designed and constructed in Korea before 1992. Important test parameters are axial load, load pattern, retrofit type. Glassfiber sheets were used for retrofitting in the plastic hinge region of concrete piers. The nonlinear behavior of bridge columns have been evaluated through their yield and ultimate strength, energy dissipation, displacement ductility and load-deflection characteristics under quasi-static cyclic loads. It can be concluded from the test that concrete piers strengthened with glassfibers have been enhanced for their ductile behavior by approximate 50%.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.453-456
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• 2003

This research is to evaluate the seismic performance of reinforced concrete bridge piers with lap-spliced longitudinal reinforcement steels in the plastic hinge region, and to develop the enhancement scheme of their seismic capacity. Six circular columns of 0.6m diameter and 1.5m height were made with two confinement steel ratios. 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 simultaneously under an axial load, P=$0.1f_{ck}A_{g}$, and residual seismic performance of damaged columns was evaluated. Test results show that RC bridge piers with lap-spliced longitudinal steels behaved with minor damage even under artificial earthquakes with 0.22g PGA, but failed at low ductility subjected to the subsequent quasi-static load test. This failure was due to the debonding of the lap splice. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region showed significant improvement both in flexural strength and displacement ductility.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.375-380
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• 2000

Experimental and numerical studies were done to investigate seismic performance of slender sheat wall with no boundary confinement. 1/3 scale-specimens that model the plastic region of long slender shear walls subjected to combined axial load and bending moment were rested to investigate strength, ductility, capacity of energy dissipation and strain distribution. The experimental results show that the slender walls fail due to early crushing in the compressive boundary, and then have very low ductility. The measured maximum compressive strain is 0.0021, which is much less then 0.004 being commonly used for estimation of ductility. The experimental results indicates that the maximum compressive strain is not a fixed value but is affected by moment gradient along the shear wall height and distance from neutral axis to the extreme compressive fiber.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.609-614
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• 1998

Lateral pressure by tied reinforcement greatly enhances the maximum strength and ductility of columns under concentric loading. The lateral confinement effects will be improves ductility of high-strength concrete. The major purpose of this paper is to study on the improvements of maximum strength and strain at the point of tied high-strength concrete columns subject to axial loads. For this purpose, this study collected the other analytical results and the experimental data that has been performed by a lot of worldwide researchers and also analyzed it statistically. As the result, the theoretical equation for predict maximum strength and strain at the point was proposed. It is based on calculation of lateral confinement pressure generate from tensile that develop in transverse reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.337-342
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• 1994

This experimental study is aiming to investigate the hysteritic behavior of high-strength R/C columns subjected to axial load and lateral load reversals. The five 1/4 scaled specimens were made of high-strength concrete with the design strength load(n=0.2f'cAg, n=0.4f'cAg) and type of transverse reinforcement. From the test results, strength and stiffness degradation of columns under higher axial load is much more serious than that under lower axial load. ductility of columns is enhansed with increasing amount of transverse reinforcement, shear strength is depended on the level of axial load.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.323-328
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• 2001

The behavior of bridge column under multi-directional loading as well as uni-directional loading need to be studied because bridge columns will be subjected to the multi-directional cyclic loading during a strong earthquake. To evaluate the capacity of columns, uni-axial cyclic loading tests and bi-axial alternate cyclic loading tests were carried out. The number of cycles of alternate bi-axial loading were determined considering the ratio of natural frequencies in two orthogonal directions. From the test results, strength degradation and ductility reduction were observed in biaxial loading conditions. Their rates were found to be more rapid in the loading pattern that was determined considering the different natural frequencies.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.81-84
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• 2006

The purpose of this study is to investigate the inelastic behavior of hollow reinforced concrete bridge piers under varying axial load. The role of the variable axial load is very important in the ductility, strength, stiffness, and energy dissipation. A computer program, named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The proposed numerical method for the inelastic behavior of hollow reinforced concrete bridge piers under varying axial load is verified by comparison with reliable experimental results.