• Structural Engineering and Mechanics
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• 제75권2호
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• pp.229-237
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• 2020

The steel slit shear wall (SSSW), made by cutting vertical slits in a steel plate, is increasingly used for the seismic protection of building structures. In the domain of thin plate shear walls, the out-of-plane buckling together with the potential fracture developed at slit ends at large lateral deformation may result in degraded shear strength and energy dissipation, which is not desirable in view of seismic design. To address this issue, the present study proposed a new type of SSSW made by intentionally introducing initial out-of-plane folding into the originally flat slitted plate. Quasi-static cyclic tests on three SSSWs with different amplitudes of introduced out-of-plane folding were conducted to study their shear strength, elastic stiffness, energy dissipation capacity and buckling behavior. By introducing proper amplitude of out-of-plane folding into the SSSW fracture at slit ends was eliminated, plumper hysteretic behavior was obtained and there was nearly no strength degradation. A method to estimate the shear strength and elastic stiffness of the new SSSW was also proposed.

• 한국지반신소재학회논문집
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• 제9권4호
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• pp.75-84
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• 2010

본 연구에서는 띠형 섬유보강재의 인장특성, 크리프 변형, 내시공성 및 내구성을 평가하기 위한 일련의 장기성능 평가시험을 수행하였다. 또한 시험결과를 바탕으로 장기설계인장강도 산정을 위한 강도감소계수를 평가하였다. 먼저, 크리프 변형 특성을 평가하기 위해 단계 등온법과 시간-온도 중첩법을 이용하였으며, 크리프 감소계수는 1.6을 적용하는 것이 바람직한 것으로 평가되었다. 다음으로 입도 조정된 화강풍화토를 성토재로 사용하여 수행한 내시공성 시험 결과, 보강재의 강도특성에 영향을 미치는 원사의 손상이 거의 없는 것으로 확인되어, 장기설계인장강도에 큰 영향을 미치지 않을 것으로 분석되었다. 마지막으로 내구성 평가 결과, 내화학성, 내미생물 및 내후성을 고려한 강도감소계수는 1.1을 적용하는 것이 합리적인 것으로 평가되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.513-516
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• 2008

최근 건설경기의 침체 및 원자재가 상승 그리고 후분양제의 시행 등으로 인해 공사기간 단축에 의한 공사비 절감에 대한 요구가 증가하고 있다. 공사기간 단축을 위한 방안으로 조강 콘크리트를 사용하여 양생기간을 단축시키는 방법이 일반적으로 사용되어지나 기존의 조강시멘트나 조강혼화제를 사용할 경우 고가의 재료비용이 소요될 뿐 아니라, 콘크리트의 초기 수화열 증가 및 작업성 저하 등의여러 가지 문제가 발생되고 있다. 본 연구에서는 조강형 결합재와 혼화제를 사용한 콘크리트의 현장에 적용하여 거푸집 탈형 시기를 앞당김으로써 공기단축에 의한 공사비 절감을 달성하고자 한다. 조강형 결합재와 혼화제를 사용한 콘크리트의 현장 적용성을 확인하기 위하여 기존의 조강시멘트와 조강혼화제를 사용한 콘크리트와 함께 경시변화시험 및 응결시간 측정시험 그리고 압축강도시험 등의 비교 시험을 실시하였다.

• 한국염색가공학회지
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• 제22권2호
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• pp.101-109
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• 2010

The objective of this study is to investigate the characteristics of natural indigo dyeing of cotton fabric. Reduction and dyeing were carried out by one-step process using an infrared dyeing machine at the liquor ratio of 1:100, and subsequently oxidation and washing in water were followed. Dye uptake was increased with the increase of indigo concentration. Over the full range of dyeing tests, the dyeing condition was optimized to $40^{\circ}C$ for 40min. For most of dye concentrations, the cotton fabrics showed mainly PB color. Maximum K/S value was shown at 4g/L of sodium hydrosulfite concentration and the color strength increased with the increase of dye concentration. Value(lightness) decreased with the increase of dye uptake irrespective of mercerization or reduction method, while the mercerized cotton showed two times higher dye uptake than the untreated cotton. Whereas hue of the untreated cotton showed large decrease of P character(5.6~3.5 PB) with the increase of dye uptake, that of the mercerized cotton increased P character(4.7~5.5 PB). Irrespective of mercerization, value and chroma decreased with the increased of dye uptake. In addition, the untreated showed lower chroma than the mercerized cotton. In the case of traditional reduction, hue of the untreated cotton was changed very little with the increase of dye uptake. For hydrosulfite reduction, P character decreased with the increase of dye uptake. The difference of hue value was small with the change of reduction method(hydrosulfite reduction or traditional fermentation). Color character was not influenced by the changed maximum absorption wavelength. Washing fastness showed 4~4/5 shade change rating without any staining. And dry rubbing fastness was good at low color strength. The bacterial reduction ratios of dyed cotton fabric were also increased.

• Composites Research
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• 제23권1호
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• pp.23-30
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• 2010

거더, 가로보와 콘크리트 상판 등을 포함한 대부분의 교량시스템은 특별직교이방성 판으로 거동한다. 일반적으로 이러한 경계조건을 갖는 단면 혹은 불규칙한 단면을 갖는 시스템은 해석적 해를 구하기가 복잡하다. 본 논문에서는 복합 재료로 만들어진 양변 단순지지된 슬래브교량의 설계적 방법을 제시하고자 한다. 복합재료로 이루어진 교량을 설계하기 위하여, 단면은 가장 경제적이면서 응력에 유리한 폼코어 형태를 채택하였고, 응력을 산출함에 있어서는 유한차분법 프로그램을 이용하였다. 본 논문에서는 치수가 증가됨에 따른 인장강도 감소율을 고려하였다. 파괴강도 해석은 본 논문에서 제시하고 있는 인장강도의 감소를 고려하여 제시하였다. 또한 이러한 경우에 대한 수치해석을 수행하였다.

• Steel and Composite Structures
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• 제51권3호
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• pp.225-241
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• 2024

For several reasons, cold-formed steel (CFS) beams are often manufactured with holes. Nevertheless, because of holes, the reduction in the web area causes a decrease in the bending strength. Edge stiffeners are presently added around the holes to improve the bending strength of flexural members. Therefore, this research studies CFSZ-beams with stiffened holes and investigates how edge stiffener affects bending strength and failure modes. Nonlinear analysis was carried out using ABAQUS software and the developed finite element (FE) model was verified against tests from previous studies. Using the verified FE model, a parametric study of 104 FE models was conducted to investigate the influence of key parameters on bending strength of Z- sections. The results indicated that the effect of holes is less noticeable in very thin Z-sections. Moreover, adding edge stiffeners around the holes improves the flexural capacity of Z-beams and sometimes restores the original bending capacity. Because the computational techniques used to solve the CFS buckling mode with stiffened holes are still unclear, a numerical method using constrained and unconstrained finite strip method (CUFSM) software was proposed to predict the elastic distortional buckling moment for a wide variety of CFSZ-sections with stiffened holes. A numerical method with two procedures was applied and validated. Upon comparison, the numerical method accurately predicted the distortional buckling moment of CFS Z-sections with stiffened holes.

• 대한기계학회논문집A
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• 제38권6호
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• pp.669-676
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• 2014

국내 승용차용 삼원촉매담체의 경우 배기가스 변환 효율이나 압력 강하 등은 엔진 효율 측면에서 만족되고 있지만 열적 내구성은 요구 내구 수명을 만족시키지 못하여 차량정비현장에서 상당한 파손사고가 발견되고 있다. 본 논문에서는 이러한 현상의 원인을 밝히기 위하여 국내 승용차용 삼원촉매담체에서 발생되는 열응력을 온도측정자료와 단순한 열응력 모델을 이용하여 구하였으며 열피로 성능은 확정론적 강도가 아닌 확률과 크기 및 피로 인자를 고려한 확률론적 설계 강도로 평가함으로서 확정론적 설계 강도에 의한 열피로 성능 평가 방법을 극복하였다.

• Steel and Composite Structures
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• 제12권5호
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• pp.379-393
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• 2012

Many steel bridge infrastructures in the world are getting older, and a large number of these structures are in need of maintenance, rehabilitation or replacement. Most of them are subjected to corrosion due to exposure to aggressive environmental conditions and inadequate maintenance, causing reduction of their carrying capacities. In order to have an adequate bridge management, it is of paramount importance to develop an efficient, accurate and rapid condition assessment method which can be used to make reliable decisions affecting the cost and safety. Therefore, a simple and accurate method of calculating remaining yield and tensile strength by using a concept of representative effective thickness with correlation of initial thickness and maximum corroded depth is proposed in this study, based on the results of many tensile coupon tests of corroded plates obtained from a steel plate girder with severe corrosion, used for about 100 years. Furthermore, a strength reduction diagram which will be very useful for bridge inspection engineers to make rational decisions about the maintenance management of aged steel bridge infrastructures is presented.

• 대한물리치료과학회지
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• 제21권1호
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• pp.53-58
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• 2014

Background : The purpose of this study is to identify the level of positive influence on the pain and the gripping power in patients with tennis elbow by comparing the TENS treatment method and the kinesio taping therapy with good accessibility among the kinesio taping therapy and electrical therapy. Methods : Targeting the patients diagnosed with tennis elbow, the subjects were categorized in groups of four, each of electrical therapy group and kinesio tape therapy group where the degree of pain reduction through VAS before and after the treatment of each group and the measurement of the degree of gripping power increase using the gripping power measurement tool as well as the pain reduction changes and gripping power increase before and after the treatment between the two groups were compared. Result : As a result, the electrical therapy group and the kinesio tape group were able to obtain the results of pain reduction and gripping power increase through VAS before and after the treatment, but for all pain reduction and gripping power increase, it had no statistically significant changes(p>.05). In addition, in the changes of pain reduction and changes of gripping power increase before and after the treatment, there were no statistically significant differences between the electrical therapy group and the kinesio tape group(p>.05). Conclusion : Based on the results so far, it is thought that the kinesio taping therapy can positively influence the pain reduction of patients with tennis elbow and increase of gripping power.

• 터널과지하공간
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• 제22권2호
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• pp.120-129
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• 2012

최근 친환경적 광산 개발에 대한 사회적 요구에 따라 갱외 시설물도 갱내화하는 경향이 있다. 지하 광산 구조물은 보통 높이보다 폭이 큰 공간을 필요로 하기 때문에 안정성 평가가 중요하다. 본 연구에서는 강도감소법을 이용하여 안전율을 분석하고, 강도감소법과 다변량 회귀분석을 조합하여 지하 광산 구조물의 규모 결정을 위한 수치해석적 설계의 접근방법을 수행하였다. 설계 매개변수는 암반의 전단강도와 측압계수 그리고 지하 광산 구조물의 폭과 설치심도이다. 지하 광산 구조물의 안정성은 입력된 매개변수의 서로 다른 조건하에서 강도 감소법으로 계산된 안전율의 개념으로 평가되었으며, 다양한 다변량 회귀분석을 통해 안전율에 대한 적합한 함수를 얻었다. 최종적으로 최적의 회귀모델을 사용하여 지하 광산 구조물의 규모 결정에 있어서의 초기 설계 정보를 제공하는 도표를 제안했다.