• 한국강구조학회 논문집
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• 제27권5호
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• pp.455-470
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• 2015

본 연구에서는 국내에서 생산되어 사용되고 있는 원형 파형강판을 대상으로 전단 및 휨 강도를 보다 정확하게 산정하기 위한 방안을 제시하고자 하였다. 국내 설계기준 및 기존 연구에 대한 비교 분석을 통하여 기존식에 대한 한계를 분석하고, 실험 및 비선형 해석을 통하여 원형 파형강판에 대한 좌굴강도 설계식을 제안하였다. 본 연구에서 제안한 전단좌굴 감소계수와 한계 판폭두께비를 이용하여 실험 및 해석결과와 비교한 결과, 상당히 유사한 거동을 나타내었다. 본 연구의 결과는 원형 파형강판의 부재 설계 및 구조성능평가에 편리하게 적용될 수 있을 것으로 판단된다.

• 한국공간구조학회논문집
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• 제24권2호
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• pp.83-90
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• 2024

Machine learning is widely applied to various engineering fields. In structural engineering area, machine learning is generally used to predict structural responses of building structures. The aging deterioration of reinforced concrete structure affects its structural behavior. Therefore, the aging deterioration of R.C. structure should be consider to exactly predict seismic responses of the structure. In this study, the machine learning based seismic response prediction model was developed. To this end, four machine learning algorithms were employed and prediction performance of each algorithm was compared. A 3-story coupled shear wall structure was selected as an example structure for numerical simulation. Artificial ground motions were generated based on domestic site characteristics. Elastic modulus, damping ratio and density were changed to considering concrete degradation due to chloride penetration and carbonation, etc. Various intensity measures were used input parameters of the training database. Performance evaluation was performed using metrics like root mean square error, mean square error, mean absolute error, and coefficient of determination. The optimization of hyperparameters was achieved through k-fold cross-validation and grid search techniques. The analysis results show that neural networks and extreme gradient boosting algorithms present good prediction performance.

• Earthquakes and Structures
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• 제21권6호
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• pp.613-625
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• 2021

Non-seismically designed eccentric reinforced concrete beam-column joints were extensively used in existing reinforced concrete frame buildings, which were found to be vulnerable to seismic action in many incidences. To provide a fundamental understanding of the seismic performance and failure mechanism of the joints, three 2/3-scale exterior beam-column joints with non-seismically designed details were cast and tested under reversed cyclic loads simulating earthquake excitation. In this investigation, particular emphasis was given on the effects of the eccentricity between the centerlines of the beam and the column. It is shown that the eccentricity had significant effects on the damage characteristics, shear strength, and displacement ductility of the specimens. In addition, shear deformation and the strain of joint hoops were found to concentrate on the eccentric face of the joint. The results demonstrated that the specimen with an eccentricity of 1/4 column width failed in a brittle manner with premature joint shear failure, while the other specimens with less or no eccentricity failed in a ductile manner with joint shear failure after beam flexural yielding. Test results are compared with those predicted by three seismic design codes and two non-seismic design codes. In general, the codes do not accurately predict the shear strength of the eccentric joints with non-seismic details.

• 콘크리트학회논문집
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• 제29권1호
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• pp.53-64
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• 2017

강섬유 보강 초고성능 콘크리트(UHPFRC)는 높은 압축강도 뿐 아니라 강섬유 보강에 의한 뛰어난 응력분산효과로 인해 높은 인장강도를 가지며, 미세균열의 확장을 통해 균열 후에도 경화거동을 하여 구조부재가 안정적으로 외력에 저항하도록 한다. 본 연구에서는 UHPFRC 재료 인장강도를 정의함에 있어 노치가 있는 휨실험과 직접인장실험을 비교하여 실험법 및 결과 분석의 장단점을 알아보았다. I-형 보의 전단부재실험은 복부의 면내전단거동을 알아보기 위하여 전단 경간비, 유효높이, 재료인장강도를 변수로 계획하였다. 실험결과를 통해 전단보강근이 없는 UHPFRC I형 보의 균열발생 이후 전단거동의 응력 재분배효과를 정량적으로 판단하고, 균열 후 거동을 기존 전단 강도식이 잘 반영하고 있는지 검토하였다. 전단철근 보강이 없는 UHPFRC 전단부재의 경우 파괴모드는 사인장 파괴로 동일하였고, 이러한 파괴모드를 가지는 부재는 전단 경간비와 유효높이에 크게 영향을 받게 되어 부재 설계 시 이러한 변수에 대한 고려가 필요한 것으로 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.101-106
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• 2003

Recent electronic equipment becomes smaller, more functional, and more complex. According to these trends, LTCC(low temperature co-fired ceramic) has been emerged as a promising technology in packaging industry. It consists of multi-layer ceramic sheet, and the circuit has 3D structure. In this technology via hole formation plays an important role because it provides an electric path for the packaging interconnection network. Therefore via hole quality is very important for ensuring performance of LTCC product. Via holes are formed on the green sheet that consists of ceramic(before sintering) layer and PET(polyethylene Terephthalate) one. In this paper we found the correlation between hole quality and process condition such as ceramic thickness, and tool size. The shear behavior of double layer sheet by micro hole punching which is different from that of single layer one was also discussed.

• Structural Monitoring and Maintenance
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• 제7권3호
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• pp.167-193
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• 2020

In this paper, the behavior of interior steel fiber reinforced concrete beam - column joints (BCJs) under cyclic loading is investigated. An experimental program including tests on twelve reinforced concrete (BCJs) specimens under cyclic loading was carried out. The test specimens are divided into two groups having different geometry: group (G1) (symmetrical BCJs specimens) and group (G2) (nonsymmetrical BCJs specimens). The parameters considered in this study are the steel fibers (SFs) content by volume of concrete (V_f), the spacing of shear reinforcement at the joint region, and the area of longitudinal flexural reinforcement. Test results show that the addition of 0.5% SFs with stirrups spacing S=S_max has effectively enhanced the overall performance of BCJs with respect to energy dissipation, ductility ratio, spreading and width of cracks. The failure of specimens is governed mainly by the formation of a plastic hinge at the face column and outside the beam-column junction. Secondary shear cracks were also observed in the beam-column junctions.

• Steel and Composite Structures
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• 제21권4호
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• pp.775-789
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• 2016

This paper presents the flexural behavior & ultimate strength performance of innovative light weight sandwich panels of size $3{\times}1.2m$ with two different solidity ratios viz. 0.5 and 0.33 under out of plane bending load. From the experimental studies, it is observed that the flexural strength and the stiffness are increased by about 46% and five folds for lesser solidity ratio case. From the measured strains of the shear connectors, full shear transfer between the concrete wythes is observed. The yielding occurred approximately at 4% and 0.55% of the ultimate deformation for 100 mm & 150 mm thick panels, which shows the large ductility characteristics of the panels. From the study, it is inferred that the light weight sandwich panels behave structurally in a very similar manner to reinforced concrete panels. Further from the numerical study, it is observed that the numerical values obtained by FE analysis are in good agreement with the experimental observations.

• 소성∙가공
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• 제13권1호
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• pp.65-71
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• 2004

Recent electronic equipment becomes smaller, more functional, and more complex. According to these trends, LTCC(low temperature co-fired ceramic) has been emerged as a promising technology in packaging industry. It consists of multi-layer ceramic sheet, and the circuit has 3D structure. In this technology via hole formation plays an important role because it provides an electric path for the packaging interconnection network. Therefore via hole qualify is very important for ensuring performance of LTCC product. Via holes are formed on the green sheet that consists of ceramic(before sintering) layer and PET(polyethylene terephthalate) one. In this paper we found the correlation between hole quality and process condition such as PET thickness and ceramic thickness. The shear behavior of double layer sheet by micro hole punching which is different from that of single layer one was also discussed.

• Advances in materials Research
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• 제5권4호
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• pp.299-318
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• 2016

Analytical investigations were performed of a longitudinal crack representing a cylindrical surface in circular shafts loaded in torsion with taking into account the non-linear material behavior. Both functionally graded and multilayered shafts were analyzed. It was assumed that the material is functionally graded in radial direction. The mechanical behavior of shafts was modeled by using non-linear constitutive relations between the shear stresses and shear strains. The fracture was studied in terms of the strain energy release rate. Within the framework of small strain approach, the strain energy release rate was derived in a function of the torsion moments in the cross-sections ahead and behind the crack front. The analytical approach developed was applied to study the fracture in a clamped circular shaft. In order to verify the solution derived, the strain energy release rate was determined also by considering the shaft complimentary strain energy. The effects were evaluated of material properties, crack location and material non-linearity on the fracture behavior. The results obtained can be applied for optimization of the shafts structure with respect to the fracture performance. It was shown that the approach developed in the present paper is very useful for studying the longitudinal fracture in circular shafts in torsion with considering the material non-linearity.

• 한국전산구조공학회논문집
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• 제22권1호
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• pp.105-115
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• 2009

휨거동을 하는 전단벽을 대상으로 동일한 총 단면적을 갖는 1개의 전단벽과 마찰형 감쇠기로 연결된 전단벽의 내진성능을 수치해석을 통해 비교하였다. KBC 2005 설계스펙트럼을 근거로 축소 조절한 7개의 지진파를 입력하중으로 마찰형 감쇠기가 설치된 전단벽의 평균응답을 분석하였다. 마찰형 감쇠기의 중요한 설계변수인 기준 마찰력인 슬립하중은 각층의 마찰형 감쇠기 위치에 생기는 수직방향 전단력의 총합의 5, 10, 20, 30, 60, 90%값으로 하여 슬립이 특정한 층에 편중되지 않도록 하였다. SeismoSturct 프로그램을 이용해 비선형시간이력 해석을 수행하여 밑면 전단력, 에너지 소산량, 1층 벽체곡률, 최상층변위 측면에서 마찰 감쇠기의 제진성능을 분석하였다. 기준마찰력의 30%이하 수준의 총 마찰력을 갖는 마찰 감쇠기가 우수한 제진성능을 보였다.