• Computers and Concrete
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• 제34권5호
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• pp.611-623
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• 2024

Concrete shear walls have a wide range of applications as one of the primary lateral load-bearing elements in the construction industry. Implementation constraints often lead to the use of lap-spliced Rebar for these walls. The presence of lap-splice allows for longitudinal reinforcement slippage in the lap-spliced region, which, if it occurs, can result in reduced ductility and undesirable seismic performance of the wall. To further investigate this matter, 32 wall models with variations in longitudinal reinforcement diameter, lap-splice length, percentage of transverse reinforcement, and debonded rebar were numerically and analytically studied using finite element analysis. The selected models were subjected to gravity and cyclic lateral loads, considering bond strength and slippage in the lap-spliced region. By comparing the obtained results, including hysteresis curves, ductility, energy dissipation, reinforcement strain, and crack propagation, with continues rebars wall, it was demonstrated that the presence of lap-spliced Rebar for longitudinal reinforcement causes slippage in the lap-spliced region and reduces the structural ductility. Additionally, the results showed that in walls with lap-spliced Rebar, the use of debonding method compensates for the weakness caused by reinforcement slippage, leading to the restoration of ductility and improvement in seismic performance of the wall while ensuring resistance.

• 한국지반공학회지:지반
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• 제12권3호
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• pp.35-48
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• 1996

보강토구조물은 흙과 보강재 사이에 큰 변형이 발생하며 보강토구조물의 파괴양상도 보강재의 미끄러짐이나 변형에 의해 지배되며, 때때로 보강재의 재료의 파괴보다는 미끄러짐에 의해 보강토구조물이 파괴되므로 큰변형이 발생하는 흙-보강재의 모델링이 필요하다. 고형 및 액체폐기물 매립장에 쓰이는 라인너 시스템은 매립장의 경사와 쓰레기하중에 의해 큰 변형이 발생하게 된다. 이러한 큰 변형의 문제는 기존의 접촉요소로써 모델링하는데 많은 제약 이 따른다. 본 논문에서는 이러한 흙과 토목섬유보강사이의 큰 만행을 모델링할 수 있는 접촉은소를 제안하였으며, 그 이론과 그 모델의 적용성에 대하여 논하였다.

• 콘크리트학회논문집
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• 제28권4호
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• pp.419-426
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• 2016

이 연구에서는 다양한 콘크리트를 갖는 전단계면에서의 전단마찰거동에 대한 횡보강근 및 압축응력의 영향을 평가하였다. 12개 직접전단실험체로부터 균열진전, 전단하중-상대 미끄러짐 관계, 균열발생시 전단응력, 최대전단내력 및 횡보강근의 전단저항력 등이 측정되었다. 실험결과 동일 전단하중에서 상대 미끄러짐 제어에 대한 횡보강근 배근형상 및 콘크리트 압축강도의 영향은 미미하였다. 작용 압축응력의 증가와 함께 콘크리트의 전단전달력을 증가하는 반면, 횡보강근의 전단전달력은 감소하였는데, 횡보강근의 전단저항은 배근형태에 의해 영향을 받지 않았다. AASHTO-LRFD, Mattock 및 Hwang and Yang의 모델은 콘크리트의 전단마찰내력을 과소평가하였다. 반면, Hwang and Yang의 모델은 실험결과와의 비교에 대한 평균과 표준편차 값이 각각 1.02과 0.23으로서 기존 모델에 비해 다양한 변수의 영향을 적절히 고려하면서 콘크리트의 전단마찰내력을 잘 예측하였다.

• Computers and Concrete
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• 제20권2호
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• pp.215-227
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• 2017

A finite element model (FEM) for predicting early-age behavior of reinforced concrete (RC) bridge deck slabs with fiber-reinforced polymer (FRP) bars is presented. In this model, the shrinkage profile of concrete accounted for the effect of surrounding conditions including air flow. The results of the model were verified against the experimental test results, published by the authors. The model was verified for cracking pattern, crack width and spacing, and reinforcement strains in the vicinity of the crack using different types and ratios of longitudinal reinforcement. The FEM was able to predict the experimental results within 6 to 10% error. The verified model was utilized to conduct a parametric study investigating the effect of four key parameters including reinforcement spacing, concrete cover, FRP bar type, and concrete compressive strength on the behavior of FRP-RC bridge deck slabs subjected to restrained shrinkage at early-age. It is concluded that a reinforcement ratio of 0.45% carbon FRP (CFRP) can control the early-age crack width and reinforcement strain in CFRP-RC members subjected to restrained shrinkage. Also, the results indicate that changing the bond-slippage characteristics (sand-coated and ribbed bars) or concrete cover had an insignificant effect on the early-age crack behavior of FRP-RC bridge deck slabs subjected to shrinkage. However, reducing bar spacing and concrete strength resulted in a decrease in crack width and reinforcement strain.

• 콘크리트학회논문집
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• 제28권5호
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• pp.555-562
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• 2016

이 연구의 목적은 부드러운 면의 시공줄눈을 가지는 콘크리트 경계면에서의 횡보강근의 전단전달력을 평가하는 것이다. 횡보강근의 배근은 전단마찰 면에 수직으로 배근한 그룹(V-type)과 $45^{\circ}$의 X형으로 교차배근 한 그룹(X-type)으로 나누었다. 전단마찰면에서 횡보강근비는 V형 철근배근의 경우 0.0045~0.0135로, X형 철근의 경우 0.0064 및 0.0045이다. 소성론의 상계치 이론(upper-bound theorem)을 기반으로 한 일체화된 콘크리트의 전단마찰모델을 수정하여, 부드러운 면의 시공줄눈을 갖는 콘크리트의 전단마찰내력을 평가하였다. 실험결과, 시공줄눈이 있는 두 부재사이의 전단마찰 내력에 대한 콘크리트 단위용적중량의 영향은 미미하였다. 시공줄눈에서 상대 미끄러짐 제어 및 전단마찰내력에 대해서는 X형 배근이 V형 배근에 비해 다소 유리하였다. 부드러운 면을 갖는 시공줄눈의 전단마찰내력에 대한 실험결과와 제안모델에 의한 예측값의 비들의 평균과 표준편차는 각각 1.07과 0.14로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.139-147
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• 1999

Six reinforced concrete shear wall, constructured with fully rigid, slit, and infilled types, were tested under both vertical and cyclic loadings. Experimental programs were carried out to evaluate the seismic performance of such test specimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility, under load reversals. All the specimens were modeled in one-third scale size. Based on the test results, the following conclusions can be made. For the diagonal reinforced slit and infilled shear wall specimens, it was found that the failure mode shows very effective crack control and crushing due to slippage prevention of boundary region and reduction of diagonal tension rathar than the brittle shear and diagonal tension failure. The ductility of specimens designed by the diagonal reinforcement for the slit and infilled shear wall was increased 1.72~1.81 times in comparison with the fully rigid shear wall frame. Maximum horizontal load-carrying capacity of specimens designed by the diagonal reinforcement ratio the slit and infilled shear wall was increased respectively by l.14 times and l.49 times in comparison with the standard fully rigid shear wall frame.

• 대한토목학회논문집
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• 제8권1호
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• pp.33-40
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• 1988

흙과 보강재 사이의 거동을 측정하는 수단으로서 hollow cylinder type의 샘플 내에 보강재를 인장방향으로 삽입하여 주위압력을 일정하게 유지한 가운데 축력(軸力)을 감소시키는 소위 삼축인장시험을 실시하였다. 인장특성(引張特性)(extensibility)이 상이(相異)한 3종류의 보강재를 사용한 결과 파괴변형율(failure strain), 최대강도후의 응력강소(loss of post-peak strength), 변형모양(deformation mode) 등이 보강재에 따라 각각 독특하였고, 파괴의 양상은 breakage 또는 pull-out 이 발생하였으며, 보강재단(補强材端)의 고정여부에 따라 보강효과가 영향을 받음이 확인되었다. 따라서 보강토해석 및 설계시 흙 및 보강재 자체의 강도(强度)와 더불어 보강재의 인장특성(引張特性)과 경계조건(境界條件)이 매우 중요한 고려요소임을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.683-688
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• 1999

The purpose of this study is to develop and evaluate the structural performance of various shear walls, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. under load reversals. For the diagonal reinforced slit and infilled shear wall specimens, it was found that the failure mode shows very effective crack control and crashing due to slippage prevention of boundary region and reduction of diagonal tension rather than the brittle shear and diagonal tension failure. The ductility of specimens designed by the diagonal reinforcement for the slit and infilled shear wall was increased 1.72~1.81 times in comparison with the fully rigid shear wall frame. Maximum horizontal load-carrying capacity of specimens designed by the diagonal reinforcement ratio the slit and infilled shear wall was increased respectively by 1.14 times and 1.49 times in comparison with the standard fully rigid shear wall frame.

• Steel and Composite Structures
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• 제37권1호
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• pp.15-26
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• 2020

The top-and-seat angles with double web angles are commonly used in the design of beam-to-column joints in Asian and North American countries. The seismic behavior analysis of these joints with large cross-section size of beam and column (often connected by four or more bolts) is a challenge due to the effects from the relatively larger size of stiffened angles and the composite action from the adjacent concrete slab. This paper presents an experimental investigation on the seismic performance of exterior composite beam-to-column joints with stiffened angles under cyclic loading. Four full-scale composite joints with different configuration (only one specimen contain top angle in concrete slab) were designed and tested. The joint specimens were designed by considering the effects of top angles, longitudinal reinforcement bars and arrangement of bolts. The behavior of the joints was carefully investigated, in terms of the failure modes, slippage, backbone curves, strength degradation, and energy dissipation abilities. It was found that the slippage between top-and-seat angles and beam flange, web angle and beam web led to a notable pinching effect, in addition, the ability of the energy dissipation was significantly reduced. The effect of anchored beams on the behavior of the joints was limited due to premature failure in concrete, the concrete slab that closes to the column flange and upper flange of beam plays an significant role when the joint subjected to the sagging moment. It is demonstrated that the ductility of the joints was significantly improved by the staggered bolts and welded longitudinal reinforcement bars.

• 콘크리트학회지
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• 제3권2호
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• pp.115-121
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• 1991

보-기둥 접합부에서 보의 축방향 철근의 슬립은 정하중 및 동하중 하에서 철근 콘크리트 골조를 손상시키는 중요한 요인중 하나이다. 이 논문은 이형철근의 국부 부착-슬립 특성에 관한 콘크리트강도 및 보강철근에 대해 실행된 실험결과를 요약하였다. 실험결과로부터 부착할렬균열(bond splitting crack)이 기둥은 축방향 철근에 의해 제어되는 한 횡방향 보강철근이 국부부착거동에 직접적인 영향을 미치지 않으며 극한부착강도는 콘크리트강도의 콘크리트강도의 제곱근에 비례해 증가함을 알 수 있었다. 이를 근거로 압축강도에 따른 보강철근 내부의 콘크리트와 이형철근의 국부 부착 응력-슬립 상관관계를 나타내는 실험모델을 유도하였다.