• Journal of the Korea Concrete Institute
• /
• v.21 no.2
• /
• pp.169-178
• /
• 2009

An equation for calculating confining reinforcement amount of RC bridge columns, specified in the current bridge design codes, has been made to provide additional load-carrying strength for concentrically loaded columns. The additional load-carrying strength will be equal to or slightly greater than the resistant strength of a column against axial load, which is lost because the cover concrete spalls off. The equation considers concrete compressive strength, yield strength of transverse reinforcement, and the section area ratio as major variables. Among those variables, the section area ratio between the gross section and the core section, varying by cover thickness, is a variable which considers the strength in the compression-controlled region. Therefore, the cross section ratio does not have a large effect in the aspect of ductile behavior of the tension-controlled region, which is governed by bending moment rather than axial force. However, the equation of the design codes for calculating confining reinforcement amount does not directly consider ductile behavior, which is an important factor for the seismic behavior of bridge columns. Consequently, if the size of section is relatively small or if the section area ratio becomes excessively large due to the cover thickness increased for durability, too large an amount of confining reinforcement will be required possibly deteriorating the constructability and economy. Against this backdrop, in this study, comparison and analysis were performed to understand how the cover thickness influences the equation for calculating the amount of confining reinforcement. An equation for calculating the amount of confining reinforcement was also modified for reasonable seismic design and the safety. In addition, appropriateness of the modified equation was examined based on the results of various test results performed at home and abroad.

• Journal of the Korea Concrete Institute
• /
• v.21 no.5
• /
• pp.629-638
• /
• 2009

In this paper, the existing formulas of the step-by-step method were generalized for effective estimation of responses of complicated composite sections due to long-term deformation of concrete. The initial transformed section properties of the composite section were derived from material and section properties of concrete section and sections which confine the longterm deformation of concrete. The transformed section properties at each step were derived from the effective modulus of elasticity considered the creep coefficient variation. Improved formulas of the step-by-step method for generalized responses were derived by introducing 5 generalized parameters. The formulas can be more simplified by applying constant increment of creep coefficient at each step. The constant increment of creep coefficient at each step can also reduce computing time and make equal computing error of each step. The generalized responses for axial elastic strain of concrete section were most sensitive to the area rate of concrete section, and the ratio of the second moment of the confining section area was more sensitive than that of the concrete section. Those for elastic curvature of concrete section were most sensitive to the ratio of the second moment of concrete section area.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.976-980
• /
• 2005

자연하천과 같은 사행수로에서 발생하는 이차류는 흐름 분포를 왜곡시킴으로써, 유사이동, 하상과 제방침식, 하천의 지형변형 등에 매우 큰 영향을 미치게 된다. 또한, 이차류는 주 흐름방향에 수직으로 발생하기 때문에 자연하천에 유입된 오염물의 횡방향 혼합에도 지대한 역할을 한다. 따라서, 본 연구에서는 사행수로에서 이차류의 특성을 정량적으로 분석하고자 중심각이 $120^{\circ}$인 두 개의 만곡부로 이루어진 사행수로에서 실험을 수행하였다. 실험수로는 직사각형 단면과 자연형 단면 두 가지 형태로 제작하였으며, 자연형 단면 하상은 베타함수를 이용하여 제작하였다. 이차류의 정확한 측정을 위해 3차원 유속측정 장치인 micro-ADV를 이용하였다. 실험조건으로는 직사각형 단면과 자연형 단면에서 평균수심과 유량을 달리하여 실험을 총 12회 수행하였다. 실험결과, 직사각형 단면수로에서의 주 흐름의 최대유속선은 수로의 가장 짧은 경로를 따라 발생하였는데, 이는 Shiono와 Muto (1998)의 결과와 일치한다. 자연형 단면 수로에서의 주 흐름은 직사각형 단면 수로에서의 주 흐름 거동과 비슷한 양상을 보였다. 이것은 실제 자연하천 만곡부에서의 주흐름 거동(최대유속선이 최심선을 따라 발생)과는 상이한 결과였다. 그 첫째 원인은 실험수로의 조도가 일반적인 실제하천의 조도를 상사법칙에 맞게 계산한 값보다 작았기 때문이다. 그리고 두 번째 원인은 실험수로의 하폭대 수심비율은 실제하천의 하폭대 수심비율보다 컸기 때문인 것으로 사료된다. 이차류의 정량적인 분석을 위해 각 측정지점별로 횡방향, 수심방향 유속을 그려본 결과, 직사각형 단면에서는 하나의 셀이 존재하는 반면에 자연형 단면에서는 셀이 두개 존재함을 알 수 있었다. 이는 자연하천에서도 발견되는 현상이다. 실제 자연하천에서는 주 셀이 바깥제방 셀보다 큰 형태를 보이지만, 실험수의에서의 셀의 형태는 주 셀보다 바깥제방 셀이 더 크게 발생하는 것으로 밝혀졌다. 이는 앞서 언급한 바와 같이 조도가 작음으로 인한 것으로 판단된다. 이차류 강도를 계산한 결과, 직사각형 단면 수로의 최대값은 두 번째 만곡 유입부지점(U2)에서 가장 크게 나타났으며. 자연형 단면 수로에서 최대값은 두 번째 만곡을 조금 지난 (U4)지점에서 가장 크게 나타났다. 자연형 단면에서는 하폭 대 수심비가 커질수록 이차류강도가 크게 나왔으나, 직사각형 단면에서는 반대로 나왔다. 그리고, 자연형 단면의 이차류 강도는 직사각형 단면보다 크게 나타났다. 특히, 직사각형 단면의 이차류강도는 첫 번째 만곡부분보다 두 번째 만곡부분이 더 크게 나타나는 현상만 보였지만, 자연형 단면의 이차류 강도는 앞서 언급한 특징 외에 만곡부에서 증가하고, 직선부에서 감소하는 주기적인 형태를 보였다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.5
• /
• pp.24-31
• /
• 2021

The soundproof tunnels have been generally designed with H-beam girders, and the high weight of H-beam may cause the excessive design of the substructure. To solve this problem, this paper proposes a new soundproof tunnel girder design composed of pipes and discontinuous plates. First, the structural behavior of the straight girder according to the design parameters was examined through finite element analysis. The arrangement and shape of the plates were determined as the design parameter, to obtain the optimal design of girder. After then, the structural behavior and buckling stability of the arched girder were subsequently evaluated. As a result of the parameter analysis, it was confirmed that the axial force acting on the girder increased and the moment decreased as the ratio of unsupported sections decreased or the number of supporting plates increased. The stress concentration on the pipe member was relieved by increasing the long axis length of the elliptical plate. Arched girder analysis showed that the structural efficiency increase as the long axis of elliptical plate increase. As a result of the buckling evaluation, the buckling threshold load of the three connected girders was about 3.7 times higher than the design load. Consequently, it was confirmed that the proposed soundproof tunnel structure design satisfies both light weight and structural safety.

• Electrical & Electronic Materials
• /
• v.3 no.2
• /
• pp.138-146
• /
• 1990

볼츠만 수송방정식에 관한 홀스타인의 식을 사용하여 온도는 273.deg.K, 상대전계의 세기가 1.leq.E/P..leq.30(V/cm Torr)인 때의 Na와 He 단일기체중을 통과하는 전자의 에너지분포함수와 수송계수를 계산하였다. 그리고 전자 이동속도의 결과치를 실험값과 비교하였으며 실험치와 계산치가 일치하도록 충돌단면적을 수정하여 계산에 적용하였다. 이러한 방법으로 Hesms 0.1[eV]-50[eV]까지 Na는 0.1[eV]-5[eV]까지의 에너지범위에서 결정된 운동량변환단면적의 값은 제한된 범위에서 Crompton 및 Nakamura의 값과 거의 일치하였다. 또한 이와 같이하여 계산된 Na와 He 단일기체의 충돌단면적을 이용하여 온도는 273.degK, 상대전계의 세기는 1.leq.E/P$_{o}$ .leq.30(V/cm Torr)의 범위에서 Na-He 혼합증기의 혼합비율을 He:Na는 99.5:0.5, 99:1, 9:1. 1:1로 변화시켜 특성에너지, 평균에너지, 전자이동속도, 전자에너지 분포함수를 게산하였다.

• 연구논문집
• /
• s.29
• /
• pp.123-130
• /
• 1999

Flow divider valve, a kind of hydraulic control valve to divide the flow from one input line to two output line uniformly, should be able to keep the constant flow to output lines despite of the change load or supply pressure. Having 5-10% flow diving error in commercial hydraulic products is one of main source of the accumulated error caused hydraulic system problem and demands the development of flow divider valve to control flow more accurately, In this paper, the dynamic characteristics of flow divider valve are investigated by the numerical estimation of the spool motion considered the external supply force. The optimum design of flow divider valve are proposed to reduce the flow diving error. For the dynamic characteristics analysis, the change of sectional area of fixed and variable orifice, and spool are studied when the input signal is accepted to a constant load.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.1
• /
• pp.36-44
• /
• 2019

The purpose of this study is to evaluate the structural performance of press-formed type asymmetric column to beam connections of steel-PC composite module frames. Most of the column sections of the joints making up the modular frame use a closed square steel section. The column-beam connection using the closed column section has difficulty in reducing the workability and securing the fire resistance. In order to overcome this disadvantage, concrete is filled in the asymmetrical open type cross section of the steel plate by press forming. A total of four specimens were fabricated to investigate the structural performance of press formed type asymmetric column to beam connections. The experimental results show that the structural performance and behavior of the asymmetric columns are different depending on whether the asymmetric column cross section is composited or the column width thickness ratio. The structural performance of the press formed type asymmetric column to beam connection was evaluated by comparing the experimental results with the theoretical formulas.

• The Journal of the Korea Contents Association
• /
• v.15 no.8
• /
• pp.53-68
• /
• 2015

This study analyzed online word-of-mouth information using content analysis to help practical categorization of two-sided eWOM. A total of 402 online consumer reviews on search goods and experience goods were collected. Descriptive characteristics(information direction, length of review line) and content structural characteristics(product benefit types, information presentation methods) were used as analysis criteria. The study results are as follows. First, the types of two-sided e-WOM direction were made of positive/negative, negative/positive, positive/negative/ positive, and negative/positive/negative. Second, the length of two-sided eWOM was longer than the length of one-sided eWOM and blended type accounted for the highest proportion both one-sided and two-sided eWOM at the aspect of product benefit. Third, holistic presentation method was overwhelmingly high in one-sided eWOM, whereas blended and analytic presentation methods were somewhat high in two-sided eWOM. Fourth, holistic presentation method was high in search goods, whereas blended and analytic presentation methods were high in experience goods. Based on these results, implications for two-sided e-WOM study and further research issues were discussed.

• Journal of Korean Association for Spatial Structures
• /
• v.9 no.3
• /
• pp.93-100
• /
• 2009

As interest in latest cultural heritance is increased, an importance about conservation of dilapidated cultural building asset is risen. Most of cultural building asset used wood by main material and conservation repair about corrosion and damage by deterioration of these cultural building asset considers cultural value of member and the basis principle is the archetype maintenance. Accordingly, conservation processing method that use synthetic is embossed. This paper experimented with reinforcement sectional area ratio, direction of section, length, strength of synthetic resins as variable and manufactures total 14 specimens as experimental study about compression reinforcement performance of circular section wood that strengthen by synthetic resins. The result of this paper has shown that adequate strengthen is more efficient than new member and the most important authenticity in strengthen and repair of cultural heritance can be ensured.

• Magazine of the Korea Concrete Institute
• /
• v.14 no.1
• /
• pp.19-22
• /
• 2002

건축공학과를 졸업하고 구조설계 실무 분야로 진출하는 이의 비율이 3~5%라는 비공식 통계가 있다. 이 통계 숫자가 말하듯이 건축구조설계업은 건축공학과 졸업자가 택하는 소수의 직업군에 속한다. 재학시에는 콘크리트 구조, 강구조 및 여타 구조 과목을 해당 분야를 전공한 교수진으로부터 각각 배우지만 실무에서는 맡겨진 프로젝트에 의해 구조 형식이 결정되고 스스로의 노력과 회사 내 시스템을 통해 해결해야 하므로 구조 형식 전반에 걸친 프로패셔널(professional)이 되어야 한다. 콘크리트에 대한 전문지식도 학교에서는 콘크리트의 기본 사항, 수직 및 수평 부재의 단면 설계 연습 등을 통해 기본적인 단계의 지식을 습득한다. 그러나 실무에서는 구조 시스템, 콘크리트 프레임의 거동 및 수많은 부재의 단면 설계 등과 같이 포괄적인 지식이 주종을 이룬다.(중략)