• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.284-291
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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 400mm diameter and 2,000mm height. Test parameters are different transverse reinforcement and loading pattern. These piers were tested under lateral load reversals with the axial load of $0.1f_{ck}A_g$. 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.

• Steel and Composite Structures
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• v.18 no.4
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• pp.971-983
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• 2015

To promote greater acceptance and use of composite RCS systems, a two-bay two-story frame specimen with improved composite RCS joint details was tested in the laboratory under reversed cyclic loading. The test revealed superior seismic performance with stable load versus story drift response and excellent deformation capacity for an inter-story drift ratio up to 1/25. It was found that the failure process of the frame meets the strong-column weak-beam criterion. Furthermore, cracking inter-story drift ratio and ultimate inter-story drift ratio both satisfy the limitation prescribed by the design code. Additionally, inter-story drift ratios at yielding and peak load stage provide reference data for Performance-Based Seismic Design (PBSD) approaches for composite RCS frames. An advantage over conventional reinforced concrete and steel moment frame systems is that the displacement ductility coefficient of the RCS frame system is much larger. To conclude, the test results prove that composite RCS frame systems perform satisfactorily under simulated earthquake action, which further validates the reliability of this innovative system. Based on the test result, some suggestions are presented for the design of composite RCS frame systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.862-873
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• 2007

Energy dissipation devices can be considered as an alternative for the seismic performance enhancement of existing structures based on the strengthened seismic design code. In this study, seismic response mitigation effects of friction dampers are investigated through the shaking table test of a full scale 3 story building structure. Frist, the bilinear force-displacement relationship of a structure-brace-friction damper system and the effect of brace-friction damper on the increase of frequency and damping ratio are identified. Second, frequency, displacement, and torque dependent characteristics of the friction damper are investigated by using harmonic load excitation tests. Finally, the shaking table tests are performed for a full scale 3 story steel frame. System identification results using random signal excitation indicated that brace-friction damper increased structural damping ratio and frequency, and El Centro earthquake test showed that brace-friction damper reduced the peak displacement and acceleration significantly. In particular, it was observed that the damping effect due to friction damper becomed obvious when the structure was excited by more intensive load causing frequent slippage of the friction dampers.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.712-715
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• 2004

Five RC piers were tested under a constant axial load and a cyclically reversed horizontal load to investigate the behavior of RC piers used in the high-strength concrete and the high-strength rebars. Seismic design of piers were conducted under the same design, according to the current Korean Bridge Design Standard. The parameters of the test were concrete compressive strength and steel strength, steel ratio. The test results indicated that RC piers of the high-strength concrete and high-strength rebars exhibited ductile behavior and seismic performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.5-8
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• 2004

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of four one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The constant vertical axial stresses applied are 0, 0.84 and 1.80MPa, while the amount of reinforcements in horizontal and vertical directions are $0\%,\;0.08\%\;and\;0.18\%$ respectively. Test results obtained for each specimen include cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Structural Engineering and Mechanics
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• v.27 no.2
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• pp.149-172
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• 2007

An experimental study of five full-scale coupling beam specimens has been conducted to investigate the seismic behavior of strengthened RC coupling beams by bolted side steel plates using a reversed cyclic loading procedure. The strengthened coupling beams are fabricated with different plate thicknesses and shear connector arrangements to study their respective effects on load-carrying capacity, strength retention, stiffness degradation, deformation capacity, and energy dissipation ability. The study revealed that putting shear connectors along the span of coupling beams produces no significant improvement to the structural performance of the strengthened beams. Translational and rotational partial interactions of the shear connectors that would weaken the load-carrying capacity of the steel plates were observed and measured. The hierarchy of failure of concrete, steel plates, and shear connectors was identified. Furthermore, detailed effects of plate buckling and various arrangements of shear connectors on the post-peak behavior of the strengthened beams are discussed.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.561-572
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• 2019

In the design criterion for the nuclear power plant piping system, the limit state of the piping against an earthquake is assumed to be plastic collapse. The failure of a common piping system, however, means the leakage caused by the cracks. Therefore, for the seismic fragility analysis of a nuclear power plant, a method capable of quantitatively expressing the failure of an actual piping system is required. In this study, it was conducted to propose a quantitative failure criterion for piping system, which is required for the seismic fragility analysis of nuclear power plants against critical accidents. The in-plane cyclic loading test was conducted to propose a quantitative failure criterion for steel pipe elbows in the nuclear power plant piping system. Nonlinear analysis was conducted using a finite element model, and the results were compared with the test results to verify the effectiveness of the finite element model. The collapse load point derived from the experiment and analysis results and the damage index based on the stress-strain relationship were defined as failure criteria, and seismic fragility analysis was conducted for the piping system of the BNL (Brookhaven National Laboratory) - NRC (Nuclear Regulatory Commission) benchmark model.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.263-272
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• 2003

Scaled model tests were carried out to investigate a seismic behavior of reinforced concrete piers with hollow-rectangular section that were not detailed for seismic load. Additional lateral reinforcing bars were not provided that might be required for confinement against earthquake load. Two kinds of reinforcement details were considered for the longitudinal reinforcing bars: lap-spliced and continuous. In the lap-spliced model all longitudinal bars were lapped at the same height in a bottom plastic hinge zone. In the other model all longitudinal bars extended continuously throughout the height. The constructed models were subjected to quasi-static cyclic lateral loading in the presence of the constant vertical load. Limited ductile behavior was observed in the test of lap-spliced model and more ductile behavior was observed in the test of a continuous longitudinal reinforcement model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.552-558
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• 2016

A control rod drive mechanism(CRDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod within a reactor core to control the reactivity of the core. The CRDM for Jordan Research and Training Reactor with 5MW power has been designed and fabricated based on the HANARO’s experience through KAERI and DAEWOO consortium. This paper describes the seismic test results to demonstrate the operability, the drop performance and the structural integrity of CRDM during or after seismic excitations. The seismic tests are carried out under 5 OBE and 1 SSE loads at three Test Rigs simulating the reactor structure and the pool top. From the tests, the CRDM is smoothly driven without a malfunction of stepping motor under OBE load. The pure drop time under OBE and SSE loads is measured as 1.169s and 1.855s to meet the design requirement. Also, it is found that the CRDM maintains the structural integrity without a change of the function and natural frequency before and after seismic loads.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.1
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• pp.21-28
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• 2021

The main purpose of this study is to assess the safety of the fixed anchorages subjected to the seismic motion for an operating facilities in the actual power plant. Thus, the experimental study was conducted to investigate the load response in the event of an actual seismic to the anchorages of a nonstructural components. Since there are economic and spatial constraints to study nonstructural components that actually have various forms, alternative test specimens of steel frames with mass were built and the shaking table test was carried out. In order to evaluate the dynamic characteristics and seismic performance, the natural frequency of the target structure was identified through the shaking table test and then the load response characteristics of the anchorage were evaluated by generating an artificial seismic effect like actual seismic. Finally, the structural stiffness was reinforced by fixing the steel frame to the test specimen using bolts, thereby reducing the load transmitted to the anchorage. It will be carried out on the reliability verification of the experiments and areas that have not been carried out due to the site conditions through the analytical approach in the future.