• 한국공간구조학회논문집
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• 제22권4호
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• pp.39-48
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• 2022

The energy dissipation of inverted V-type eccentric steel braced frames can be achieved through the yielding of a slit link, through yielding of a number of strips between slits when the frame is subjected to inelastic cyclic deformation. On the other hand, the development of seismic resistance system without residual deformation is obtained by applying the superelasdtic shape memory alloy (SMA) material into the brace and link elements. This paper presents results from a systematic three-dimensional nonlinear finite element analysis on the structural behavior of the eccentric bracing systems subjected to cyclic loadings. A wide scope of structural behaviors explains the horizontal stiffness, hysteretic behaviors, and failure modes of the recentering eccentric bracing system. The accurate results presented here serve as benchmark data for comparison with results obtained using modern experimental testing and alternative theoretical approaches.

• 한국공간구조학회논문집
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• 제22권4호
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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.

• Earthquakes and Structures
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• 제25권4호
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• pp.283-296
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• 2023

This paper presents experimental and numerical studies of seismic performance on reinforced concrete (RC) wide beam (WB) joints. Two RC-WB joint specimens and one conventional RC joint specimen were fabricated using the reinforcing details of longitudinal reinforcing bars in a beam as a variable, and quasi-static cyclic loading tests were performed. The results were used to compare and analyze the load-drift ratio relationship, failure mode, and seismic performance of the specimens quantitatively. In addition, a finite element (FE) analysis of the RC-WB joint was conducted, and the rationality of the FE model was validated by comparing it with the test results. Based on the FE model, a parametric study was conducted, where the ratio of longitudinal reinforcing bars placed on the outer and inner parts of the joint (𝜌_ex/𝜌_in) was a key variable. The results showed that, in the RC-WB joint, an increase of 𝜌_ex/𝜌_in leads to more severe damage to concrete, which reduces the seismic performance of the RC-WB joints.

• Steel and Composite Structures
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• 제51권1호
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• pp.53-61
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• 2024

Aluminum foams sandwich panel (AFSP) has been used in engineering field, where cyclic loading is used in most of the applications. In this paper, the fatigue life of AFSP prepared by the bonding method was investigated through a three-point bending test. The mathematical statistics method was used to analyze the influence of different plate thicknesses and core densities on the bending fatigue life. The macroscopic fatigue failure modes and damage mechanisms were observed by scanning electron microscopy (SEM). The results indicate that panel thickness and core layer density have a significant influence on the bending fatigue life of AFSP and their dispersion. The damage mechanism of fatigue failure to cells in aluminum foam is that the initial fatigue crack begins the cell wall, the thinnest position of the cell wall or the intersection of the cell wall and the cell ridge, where stress concentrations are more likely to occur. The fatigue failure of aluminum foam core usually starts from the semi-closed unit of the lower layer, and the fatigue crack propagates layer by layer along the direction of the maximum shear stress. The results can provide a reference for the practical engineering design and application of AFSP.

• 대한전자공학회논문지SD
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• 제46권11호
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• pp.92-100
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• 2009

본 논문은 LLR-BP 복호 알고리즘을 사용하는 LDPC 복호기의 하드웨어 구조 분석하고 효율적인 복호기의 설계 방법들을 제시하였다. 또한 설계 시 복호 성능 및 하드웨어 복잡도에 영향을 미칠 수 있는 다양한 설계 이슈들을 제시하고 복호 성능의 변화를 모의실험을 통하여 분석하였다. 오류확률을 전달하는 메시지의 양자화는 정수부 3비트, 소수부 4비트를 할당하였고, 복호 성능이 저하되지 않도록 사전정보에 정수부 2비트, 소수부 4비트를 할당하였으며 LUT로 구현되는 $\Psi$(x) 함수를 조합회로인 PWL 블록으로 대체하여 하드웨어 구조의 개선에 대해 논의하였다. 복호 시간을 단축하기 위하여 중첩 스케줄링을 적용하고, 각 복호기 구조 및 설계 변수들의 제한에 따른 하드웨어 자원을 비교함으로써, 하드웨어 복잡도를 분석하였다.

• 대한전자공학회논문지SD
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• 제49권3호
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• pp.1-7
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• 2012

본 논문에서는 모바일 정보기기의 배터리 전력 관리를 제어하는 IBS(Intelligent Battery sensor), BMS(Battery Management System) 등의 PMIC(Power Management IC) 기술에 적합한 9b 2MHz 사이클릭 폴딩 ADC(Analog-to-Digital Converter)를 제안한다. 제안하는 ADC는 응용기술에 적합한 고해상도를 만족시키는 동시에 폴딩 신호처리를 사용함으로써 고속 동작이 가능하다. 또한 폴딩 블록의 하나의 단만을 반복적으로 순환하는 구조로 설계되기 때문에 전체 크기가 줄어들 뿐 아니라 전력소모도 최소화 할 수 있다. 제안하는 시제품 ADC는 0.35um 2P4M CMOS 공정으로 제작되었으며, 측정된 INL 및 DNL은 각각 ${\pm}1.5/{\pm}1.0\;LSB$ 이내로 들어온 것을 확인하였다. 또한 2MS/s 동작 속도에서 SNDR 및 SFDR 이 각각 최대 48dB, 60dB이고, 전력 소모는 3.3V 전원 전압에서 110mW 이며 제작된 ADC의 칩 면적은 $10mm^2$이다.

• 한국지반공학회논문집
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• 제21권8호
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• pp.13-26
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• 2005

모래의 aging현상은 점성토에 비하여 무시할 정도로 매우 작아서 1980년대 초까지는 거의 연구되지 않았다. 그러나 퇴적이나 교란 후 시간경과에 따라 관입저항치의 증가가 관찰되면서 현장시험을 중심으로 모래의 aging 효과에 대하여 활발한 조사가 이루어졌고, 최근에는 현장시험뿐만 아니라 실내시험에서도 여러 연구자들에 의해 모래의 aging 효과가 규명되어지고 있다. 본 연구에서는 모래의 비배수 반복전단거동에 대한 aging효과를 살펴보기 위해 낙동강 모래를 이용하여 상대밀도$(D_r)$, 압밀응력비$(K_c)$ 그리고 압밀시간을 달리하여 비배수 반복삼축압축시험을 실시하였다. 시험결과, 비배수 반복전단강도$(R_f)$는 압밀시간에 따라 증가한다는 사실을 확인할 수 있었다. 본 시험결과에서 나타난 aging 에 따른 $R_f$ 증가율을 이용하여 낙동강 모래지반의 지진규모별 비배수 반복전단강도의 현장적용 범위를 제안하였다.

• Steel and Composite Structures
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• 제37권3호
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• pp.323-339
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• 2020

In steel framed-tube structures (SFTSs), the plastic hinges at beam-ends cannot be adequately improved because of the large cross sections of spandrel beams, which results in the lower ductility and energy dissipation capacities of traditional SFTSs. To address this drawback, high-strength steel fabricated SFTSs with bolted web-connected replaceable shear links (HSFTS-SLs) have been proposed. In this system, shear links use conventional steel and are placed in the middle of the deep spandrel beams to act as energy dissipative components. In this study, 2/3-scaled HSFTS-SL specimens were fabricated, and cyclic loading tests were carried out to study the seismic performance of both specimens. The finite element models (FEMs) of the two specimens were established and the numerical results were compared with the test results. The results showed that the specimens had good ductility and energy dissipation capacities due to the reliable deformation capacities. The specimens presented the expected failure modes. Using a shorter shear link can provide a higher load-carrying capacity and initial elastic lateral stiffness but induces lower ductility and energy dissipation capacity in HSFTS-SLs. The performance of the specimens was comparable to that of the original sub-structure specimens after replacing shear links. Additionally, the expected post-earthquake recoverability and resilience of the structures could be achieved by replacing shear links. The acceptable residual interstory drift that allows for easy replacement of the bolted web-connected shear link was 0.23%. The bolted web-connected shear links had reliable hysteretic responses and deformation capacities. The connection rotation had a notable contribution to total link rotation. The results of the numerical analysis run for the proposed FEMs were consistent with the test results. It showed that the proposed FEMs could be used to investigate the seismic performance of the HSFTS-SL.

• Earthquakes and Structures
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• 제15권5호
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• pp.499-511
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• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• Advances in concrete construction
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• 제8권4호
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• pp.257-267
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• 2019

This paper presents the results of cyclic loading tests on new high-strength concrete (HC) short columns. The seismic performance and deformation capacity of three reinforced high-strength concrete filled Polyvinyl Chloride tube (RHC-PVCT) short columns and one reinforced high-strength concrete (RHC), under pseudo-static tests (PSTs) with vertical axial force was evaluated. The main design parameters of the columns in the tests were the axial compression ratio, confinement type, concrete strength, height-diameter ratio of PVCT. The failure modes, hysteretic curves, skeleton curves of short columns were presented and analyzed. Placing PVCT in the RHC column could be remarkably improved the ultimate strength and energy dissipation of columns. However, no fiber element models have been formulated for computing the seismic responses of RHC-PVCT columns with PVT tubes filled with high-strength concrete. Nonlinear finite element method (FEM) was conducted to predict seismic behaviors. Finite element models were verified through a comparison of FEM results with experimental results. A parametric study was then performed using validated FEM models to investigate the effect of several parameters on the mechanical properties of RHC-PVCT short columns. The parameters study indicated that the concrete strength and the ratio of diameter to height affected the seismic performance of RHC-PVCT short column significantly.