• 대한화학회지
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• 제9권3호
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• pp.124-127
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• 1965

The surface tension of the solution of dodecylpridinium bromide was measured by the ring method over the range $25^{\circ}\; to\; 45^{\circ}C.$ The critical micelle concentration was determined from the change of the surface tension of solution with concentration. The temperature dependence of the critical micelle concentration was also investigated. The result was compared with Adderson and Taylor's data determined by the conductivity method.

• 한국지반신소재학회논문집
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• 제22권4호
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• pp.17-26
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• 2023

강연선의 손상 및 파단위험에 대하여 적극적으로 대처하기 위해서는 기존의 사후 유지관리 체계만으로는 한계가 있으며 시설물의 내구성, 안전성 저하를 정량적으로 평가 및 예측하고 시설물의 자산가치를 고려한 합리적인 유지관리 체계의 구축이 요구된다. 따라서 가설앵커에 큰 결함이 발생하기 전 사전조치가 이루어지도록 하는 선제적 유지관리 방안을 고려해볼 가치가 있다. 이를 위해 본 연구에서는 선제적 과긴장 공법을 고안하여 설계 및 현장시험을 통해 그 효과를 검토하고 신뢰성 기반 최적화 설계를 수행하여 저항계수를 산정하였다. 이때 과긴장 앵커의 흙막이 가시설 지지효과는 강연선 파단전 유효긴장력에 대한 강연선 파단후 잔존긴장력의 비를 이용하여 평가하였으며 저항계수는 각 확률변수에 대한 최적해를 Excel solver를 이용하여 구하고 이를 한계상태식에 적용하여 산정하였다. 연구결과 과긴장률이 125%~130%인 경우 강연선 파단 후에도 높은 흙막이 가시설 지지효과를 보였으며 최적화 설계결과 하중계수(γ)는 1.25, 저항계수 Φ₁, Φ₂, Φ₃은 0.7, 0.5, 0.6을 적용함이 적절한 것으로 나타났다.

• 기술발표회
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• 통권2006호
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• pp.66-72
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• 2006

The ground anchoring has been utilized over 40 years. It is growing the application of the removal ground anchor with tension force for holding earth retaining constructions in the city. It transmits tension stress of prestressed steel wire through grouting to fixed the ground that is of great advantage adjacent ground stability. Nowadays, we can find the compression dispersion anchor on many site. But, it has some problems in behavior of anchors because of impossible to tense p.c strand uniformly under the existing equipment due to different length of p c strand. Hence, motive of this research was to study the application of the newly developed tension system, that analyze and compare with the current anchoring method build on the data of in-site test and laboratory test. As a result, in case of auto back tension system, it became clear that tension pressure was equally distributed among the steal wires but the existing tension system showed sign of instability by indicating stress deflection of about 30% compare with design load. This can cause an ultimate failure of the concentrated p.c strand and a shear failure of ground.

• 한국공간구조학회논문집
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• 제16권2호
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• pp.39-45
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• 2016

Membrane structure is a system that is stabilized by maintaining a tensile state of the membrane material that originally cannot resist the bending or pressure. Also, it is a system that allows the whole membrane structure to bear external loads caused by wind or precipitation such as snow, rain and etc. Tension relaxation phenomenon can transpire to the tension that is introduced to the fabric over time, due to the innate characteristics of the membrane material. Thus, it is important to accurately understand the size of the membrane tension after the completion of the structures, for maintenance and management purposes. The authors have proposed the principle of theoretically and indirectly measuring the tension by vibrating the membrane surface with sound waves exposures against the surface, which is compartmentalized by a rectangular boundary, and by measuring the natural frequency of the membrane surface that selectively resonates. The authors of this paper measured the tension of preexisting membrane structure for its maintenance by using the developed portable measurement equipment. Through analyzing the measurement data, the authors review the points that should be improved and the technical method for the new maintenance system of membrane tension.

• Steel and Composite Structures
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• 제37권1호
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• pp.37-49
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• 2020

In this paper, free vibration finite element analysis of axially moving laminated composite beams subjected to axial tension is studied. It is assumed that the beam has a constant axial velocity and is subject to uniform axial tension. The analysis is based on higher-order theories that have been presented by Carrera Unified Formulation (CUF). In the CUF technique, the three dimensional (3D) displacement fields are expressed as the approximation of the arbitrary order of the displacement unknowns over the cross-section. This higher-order expansion is considered in equivalent single layer (ESL) model. The governing equations of motion are obtained via Hamilton's principle. Finally, several numerical examples are presented and the effect of the ply-angle, travelling speed and axial tension on the natural frequencies and beam stability are demonstrated.

• 해양환경안전학회지
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• 제21권6호
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• pp.778-783
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• 2015

본 연구는 해상에서의 안전사고의 경감과 국민의 생명을 보호하기 위한 목적으로 자체 연구를 수행하여 FRP의 수리공법인 Butt Joint, Lap Joint, V-Scarf Joint(12t, 16t, 20t), X-Scarf Joint(12t 16t, 20t)의 인장강도와 굽힘강도를 통해 이음방식에 따른 구조강도 특성을 실험하였다. 이음 방법에 따른 인장강도와 굽힘강도의 시험편을 종합 분석한 결과, 인장강도의 강도와 굽힘강도의 그래프 패턴은 비슷한 양상으로 증가와 감소를 하였으며, 인장강도와 굽힘강도 모두 X-Scarf-Butt Joint-V-Scarf-Lap Joint 순으로 강도가 우수하였다. 인장강도는 강도특성이 가장 우수한 X-Scarf라 하더라도 Basic Material의 57% 수준의 강도를 나타내었고 굽힘강도는 X-Scarf가 Basic Material의 77% 수준의 강도를 나타내었다. 종합적으로 Over-Lay 구분을 포함하여 X-Scarf 12t 이음이 인장강도, 굽힘강도 특성이 우수하였으며 Lap Joint가 가장 좋지 않았다. Scarf 이음시 Taper 길이에 따른 강도의 차이는 V-Scarf 이음은 Taper의 길이가 가장 큰 20t가 인장강도, 굽힘강도 특성이 우수한 반면 X-Scarf 이음은 Taper의 길이가 가장 짧은 12t가 인장강도, 굽힘강도 특성이 우수하여 상반되는 결과를 나타내었다. 선박에는 많은 Stress가 작용하여 시험편만을 가지고 실험한 본 연구와 직접적인 비교는 힘들지만, 재료의 가장 기본 특성을 인장강도와 굽힘강도 시험을 통해 확인할 수 있다. FRP 국부적인 수리 방법인 Butt Joint, Lap Joint, V-Scarf, X-Scarf 4가지의 이음방법에 따른 시험값과 모재 대비 감소되는 비율을 제시하였고 추가적으로 V-Scarf와 X-Scarf의 Taper 길이별 특성을 12t, 16t, 20t로 구분한 결과값을 제시함으로써 수리 현장에서의 위치별 특성에 맞는 수리 방법의 응용이 가능하도록 하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.290-295
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• 1992

Tendon driven method to drive one joint using two actuators is developed and implemented. While the method has advantages over conventional transmissions, it also has several drawbacks like tendon slack, elongation and endurability. In this paper, a compensation method of the intrinsic non-linearities of tendon is proposed to improve the performance of antagonistic tendon driven method. In this method, tendon tension measurement is prerequisite which is measured with strain gauge type tension sensor. The developed method is implemented on one link test bed with colocated and non-colocated position sensor.

• Journal of Advanced Marine Engineering and Technology
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• 제20권4호
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• pp.101-107
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• 1996

This test was performed on the hydraulic automatic gauge control(AGC) system of adaptive mass flow method. Fundamental purpose of this study are performance evaluation of this AGC system under the actual rolling condition. It was concluded that the response of AGC system depends on the dynamic characteristics of a reel motor or roll position. The test results are as follows : 1) The control method of reel motor current is better than than of the roll position as AGC system. 2) The more steel strip thickness of delivery side is thick, the larger the gauge deviation is large, and the more it is thin, the larger the gauge deviation rate is large. 3) Because the gauge deviation is large at acceleration and deceleration speed than steady speed, so AGC system is better to adopt over 50m/min. By applying this AGC system, not only the accurary in strip thickness were improved but also productivity was improved dramatically.

• Structural Engineering and Mechanics
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• 제65권2호
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• pp.183-190
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• 2018

The prestressed concrete (PSC) technology that was first developed by Freyssinet has significantly improved over the past century in terms of materials and structural design in order to build longer, slender, and more economic structures. The application of prestressing method in structures, which is determined by the pre-tension or post-tension processes, is also affected by the surrounding conditions such as the construction site, workforce skills, and local transportation regulations. This study proposes a prestressed concrete girder design based on a hybrid segment concept. The adopted approach combines both pre-tension and post-tension methods along a simple span bridge girder. The girder was designed using newly developed 2400 MPa PS strands and 60 MPa high-strength concrete. The new concept and high strength materials allowed longer span, lower girder depth, less materials, and slender design without affecting the lateral stability of the girder. In order to validate the applicability of the proposed hybrid prestressed segments girder, a full-scale 35 m girder was fabricated, and experimental tests were performed under various fatigue and static loading conditions. The experimental results confirmed the feasibility of the proposed long-span girder as its performance meets the railway girder standards. In addition, the comparison between the measured load-displacement curve and the simulation results indicate that simulation analysis can predict the behavior of hybrid segments girders.

• 한국안전학회지
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• 제20권1호
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• pp.62-67
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• 2005

An eccentrically-loaded single edge crack tension specimen (ESET) is similar to a compact tension(CT) specimen loaded in tension-tension. The standard ESET specimen exhibits advantages over other types of cracked specimen, such as n, single-edge crack, and middle-crack tension specimen. The details of ESET specimen configuration, test procedure, and calculations are described in ASTM E647 standard. However, a difficulty in attaching COD gage to the knife-edge on the front foe of the specimen can be found when the size of ESET specimen is small for rapid cooling and heating in thermal fatigue testing. The finite element analysis is performed for the ESET specimen with projected knife-edge on the front foe and a crack-length-compliance equation is suggested for the new specimen configuration. Calibration test are conducted with 347 stainless steel to compare the measured crack length with the calculated crack length from the suggested compliance expression. The test results showed good agreements with those of analysis.