• Journal of Korean Association for Spatial Structures
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• v.22 no.4
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• pp.23-30
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• 2022

It is effective to apply hybrid damping device that combine separate damping device to cope with various seismic load. In this study, HRS hybrid damper(hybrid rubber slit damper) in which high damping rubber and steel slit plate are combined in parallel was proposed and structural performance tests were performed to review the suitability for seismic performance. Cyclic Loading tests were performed in accordance with criteria presented in KDS 41 17 00 and MOE 2019. As a result of the test, the criteria of KDS 41 17 00 and MOE2019 was satisfied, and the amount of energy dissipation increased due to the shear deformation of the high-damping rubber at low displacement. Result of performing the RC frame test, the allowable story drift ratio was satisfied, and the amount of energy dissipation increased in the reinforced specimen compared to the non-reinforced specimen.

• Steel and Composite Structures
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• v.44 no.6
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• pp.899-912
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• 2022

To study the seismic performance of the all-steel buckling-restrained brace (BRB) using the novel soft steel LY315 for core member, a total of three identical BRBs were designed and a series of experimental and numerical studies were conducted. First, monotonic and cyclic loading tests were carried out to obtain the mechanical properties of LY315 steel. In addition, the parameters of the Chaboche model were calibrated based on the test results and then verified using ABAQUS. Second, three BRB specimens were tested under cyclic loads to investigate the seismic performance. The failure modes of all the specimens were identified and discussed. The test results indicate that the BRBs exhibit excellent energy dissipation capacity, good ductility, and excellent low-cycle fatigue performance. Then, a finite element (FE) model was established and verified with the test results. Furthermore, a parametric study was performed to further investigate the effects of gap size, restraining ratio, slenderness ratio of the yielding segment, and material properties of the core member on the load capacity and energy dissipation capacity of BRBs.

• Structural Engineering and Mechanics
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• v.67 no.3
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• pp.233-244
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• 2018

This study aims at evaluating the performance of repairing technique with CFRPs in recovering cyclic performance of damaged columns in flexure in terms of structural response parameters such as strength, dissipated energy, stiffness degradation. A 2/3 scaled substandard reinforced concrete frame was constructed to represent the substandard RC buildings especially in developing countries. These substandard buildings have several structural deficiencies such as strong beam-weak column phenomenon, improper reinforcement detailing and poor material properties. Flexural plastic hinges occurred at the columns ends after testing the substandard specimen under both constant axial load and reversed cyclic lateral loading. Afterwards, the damaged columns were externally wrapped with CFRP sheets both in transverse and longitudinal directions and then retested under the same loading protocol. In addition, ambient vibration measurements were taken from the undamaged, damaged and the repaired specimens at each structural repair steps to identify the effectiveness of each repairing step by monitoring the change in the natural frequencies of the tested specimen. The ambient vibration test results showed that the applied repairing technique with external CFRP wrapping was proved to recover stiffness of the pre-damaged specimen. Moreover, the lateral load capacity of the pre-damaged substandard RC frame was restored with externally bonded CFRP sheets.

• Steel and Composite Structures
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• v.6 no.4
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• pp.303-317
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• 2006

The connection with combined cross diaphragm is developed for the connection of square CFT column and steel beam and proposed to be used for the frame with asymmetric span length. The structural characteristics of this connection lie in the penetration of the beam flange in the direction of major axis through the column for the smooth flow of stress. The purpose of this study is to analyze the dynamic behavior and stress flow of suggested connection and to evaluate the resistance to shock of connection. Four T-type CFT column-to-beam specimens; two with combined cross diaphragm and the others with interior and through diaphragms, the existing connection types, were made for cyclic load test guided by the load program of ANSI/AISC SSPEC 2002. The results show that the proposed connection is more efficient than existing ones in terms of strength, stress flow and energy absorption and satisfies the seismic performance required in the region of weak/moderate earthquakes.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.269-274
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• 2004

The performance of a newly designed wastewater treatment process equipped with an anaerobic and two intermittent aeration tanks operated alternately was investigated. During the experimental period, several types of cyclic operating schedules with different aeration and non aeration time were examined for the optimization. At all modes, the removals of organic matter and SS were highly achieved. With respect to T-N removal, however, the cycle length for aeration on/off affected the efficiencies. At the optimal operating mode, the ORP bending point indicating the disappearance of nitrate was observed. Considering the influent wastewater characteristics and cyclic operating schedules, it can be suggested that T-P removal is much more BOD/T-P ratio and/or its load dependant rather than the aeration on/off time. The results obtained from pilot-scale test showed the competitive advantage of this alternating process through an omission of nitrate recycle and operational flexibility against influent load variations when comparing with other continuous flow processes.

• Steel and Composite Structures
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• v.32 no.2
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• pp.199-212
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• 2019

This paper presents an investigation on seismic behavior of out-of-code Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns made up of high-strength (HS) steel tubes (yield strength $f_y{\geq}690MPa$). Eight Q690 circular HCFTST columns with various diameter-to-thickness (D/t) ratios, concrete cylinder compressive strengths ($f_c$) and axial compression ratios (n) were tested under the constant axial loading and reversed cyclic lateral loading. The obtained lateral load-displacement hysteretic curves, energy dissipation, skeleton curves and ductility, and stiffness degradation were analyzed in detail to reflect the influences of tested parameters. Subsequently, a simplified shear strength model was derived and validated by the test results. Finally, a finite element analysis (FEA) model incorporating a stress triaxiality dependent fracture criterion was established to simulate the seismic behavior. The systematic investigation indicates the following: compared to the D/t ratio and axial compression ratio, improving the concrete compressive strength (e.g., the HS thin-walled steel tube filled with HS concrete) had a slight influence on the ductility but an obvious enhancement of energy dissipation and peak load; the simplified shear strength model based on truss mechanism accurately predicted the shear-resisting capacity; and the established FEA model incorporating steel fracture criterion simulated well the seismic behavior (e.g., hysteretic curve, local buckling and fracture), which can be applied to the seismic analysis and design of Q690 circular HCFTST columns.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.9-14
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• 2017

In the present work, a mechanical performances under cyclic loading in RC (Reinforced Concrete) beams with normal steel and FRPH (Fiber Reinforced Plastic Hybrid) bar are investigated. For the work, RC beam members with $200{\times}200{\times}2175mm$ of geometry and 24 Mpa of design strength are prepared, and 4-point-bending tests are performed for evaluation of cracking, yielding, and ultimate loads. Through static loading test, 48.9kN and 36.0 kN of yielding loads are measured for normal RC and FRPH beam, respectively. They have almost same ultimate load of 50.0 kN. Typical tension hardening behavior is observed in FRPH beam, which is caused by the behavior of FRPH bar with tension hardening. In cyclic loading conditions, FRPH beam has more smaller crack width and scattered crack pattern, and it shows more elastic recovery than normal RC beam. The energy dissipation ratio in FRPH beam is 0.83, which is greater than 0.62 in normal RC beam and it shows more effective resistance to cyclic loadings.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.93-102
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• 2013

This paper describes the experimental study on the structural behavior of the vertical plane connection between a reinforced concrete wall and a steel plate concrete wall under out-of-plane flexural loads. The specimen was tested under a dynamic test with the use of cyclic loads. As a result of the test, ductile failure mode of vertical bars was shown under a push load and the failure load was more than that of the nominal strength of the specimen. However, the shear failure mode of the connection was confirmed in case of a pull test and thus demonstrates a need for a shear reinforcement.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.823-832
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• 2004

The purpose of this research is to investigate the flexure-shear behavior of bridge columns under seismic loads. Four full scale circular reinforced concrete columns were tested under cyclic lateral load with constant axial load. The selected test variables are aspect ratio(1.825, 2.5, 4.0), transverse steel configuration, and longitudinal steel ratio. Volumetric ratio of transverse hoop of all the columns is 0.0023 in the plastic hinge region. It corresponds to $24\%$ of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. The columns showed flexural failure or flexure-shear failure depending on the test variables. Failure behavior and seismic performance are investigated and discussed in this paper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.267-275
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• 2012

This paper describes the experimental study on the structural behavior of the joint plane between a RC(Reinforced Concrete) wall and a SC(Steel Plate Concrete) wall under out-of plane flexural loads and in-plane shear loads. The test specimens were produced with L and I shape to assess efficiently flexural and shear behavior of the structures. In order to consider dynamic loads such as earthquake, cyclic loading tests were carried out. As results of the out-of plane flexural tests, ductile failure mode of vertical bars was shown under a push load and the failure load was more than nominal strength of the specimen. And the latter test was performed to verify the variation which was composition presence of horizontal bars in the SC member. The test results showed that capacity of the specimens was more than their nominal strength regardless of composition presence of horizontal bars.