• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.215-226
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• 2015

In this study, with variables the cross section area ($97m^2$, $58m^2$, $38m^2$) and the wind velocity(0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 m/s), the time of getting off train dependent on the way of itself and the width of the evacuation route was analyzed, and also fire and evacuation characteristics is reviewed by cross section area of each wind velocity. As the result, if cross section become smaller, the density of harmful gases in the tunnel increased more than the ratio of decreasing cross section area. In the case of small cross sectional area, the surrounding environment from initial fire is indicated to exceed the limit criteria suggested in performance based design. In the analysis of effective evacuation time for evacuation characteristics, the effective evacuation time was the shortest in the case of evaluating effective evacuation time by the visibility. Also, there was significant difference between the effective evacuation time on the basis of performance based evaluation and the effective evacuation time obtained by analyzing FED (Fractional effective dose), one of the analysis method obtaining the point that deaths occur, against harmful gases.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.217-231
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• 2012

The flexural behavior of HSB I-girder with a non-slender web attributed to inelastic lateral-torsional buckling under uniform bending was investigated using nonlinear finite element analysis of ABAQUS. The girder was assumed to have a compact or noncompact web in order to prevent premature bend-buckling of the web. The unbraced length of the girder was selected so that inelastic lateral-torsional buckling governs the ultimate flexural strength. The compression flange was also assumed to be either compact or noncompact to prevent local buckling of the elastic flange. Both homogeneous sections fabricated from HSB600 or HSB800 steel and hybrid sections with HSB800 flanges and SM570-TMC web were considered. In the FE analysis, the flanges and web of I-girder were modeled as thin shell elements. Initial imperfections and residual stresses were imposed on the FE model. An elasto-plastic strain hardening material was assumed for steel. After establishing the validity of the present FE analysis by comparing FE results with test results in existing literature, the effects of initial imperfection and residual stress on the inelastic lateral-torsional buckling behavior were analyzed. Finite element analysis results for 96 sections demonstrated that the current inelastic strength equations for the compression flange in AASHTO LTFD can be applied to predict the inelastic lateral torsional buckling strength of homogeneous and hybrid HSB I-girders with a non-slender web.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.151-152
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• 2003

최근 NMR, MRI, x-선 등 전자파의 기술이 발전되면서 이들을 이용하여 내부품질을 검출하는 보다진보된 연구가 수행되고 있다. 관련 연구로는 자기공명영상을 이용하여 내공수삼 및 정상수삼의 내부를 촬영하여 T$_1$, T$_2$의 값을 측정하여 내부조직의 이상유무를 추정하였고, 또한 MRI에 의해 수삼의 내부품질 뿐만 아니라 연근 판정 가능성을 검토하는 등 많은 연구가 수행되고있다. 이 연구에서는 MRI 시스템을 이용하여 수삼의 내부단면 영상을 획득하여 내부결함 유무를 검출하고, 또한 동일한 수삼을 대상으로 홍삼 제조 후 내부품질의 변화 특성을 조사하고자 수행하였다. 공시재료는 충북 음성에 있는 인삼연초연구원에서 4~6년 근 된 수삼을 이용하였고, 시험 장비로는 국내 MRI 생산 전문 업체인 ISOL Tech. Co.에서 개발한 의료용 장비인 CHORUS 1.5T(자속밀도 1.5 Tesla)를 이용하였다. 슬라이스 두께/간격은 5mn/5mn, 촬영 단면수는 15장/시료, 영상영역(FOV)은 180mmx90mm, image size는 256$\times$128 pixels 그리고 TR/TE는 각각의 이완상수별로 500/13(Tl), 4,000/63(T2) 및 2,200/21(Pd)에 대한 단면영상을 얻었다. 5개의 수삼을 동시에 뇌두에서 뿌리 쪽으로 MR 단면영상을 획득하였다. 이완상수 T$_1$, T$_2$, Pd에 대해서 MR 영상을 획득하였으며, 총 15장의 단면 영상 중 내부 상태를 가장 잘 식별 할 수 있는 영상을 조사한 결과 T$_1$과 Pd에서 촬영한 영상에서는 내부상태가 잘 나타났으나, T$_2$에서 얻은 영상은 영상의 손실이 많이 발생되었다. 한편, T$_1$에 대해서 뇌두에서 뿌리쪽으로 가면서 각 위치에 따라 수삼 내부의 부패된 영상이 나타나 이에 대한 판정은 가능한 것으로 나타났다. 2000년도와 2001년도에 각각 수확.저장된 수삼을 부위별로 단면영상을 MRI로 측정하고, 그 시료를 인삼연초연구원(음성시험장)에서 홍삼으로 제조한 후 수삼 상태에서의 내부품질과 홍삼으로 제조된 후의 내부품질 변화를 조사하였다. 총 20본의 수삼을 MRI 시스템으로 영상을 획득하였고, 모든 시료에 대해서 내부조직의 상태를 관찰하였다. 수삼의 수분함량은 뇌두로부터 1cm부위를 절단하여 조사하였고, 수삼조직은 절단시 단면의 달관 조사에 의한 성적이며 홍삼품질은 제조삼의 조직상태를 절단하여 육안판별로 검사하였다. 총 20본의 수삼 중 정상은 16본 이었고, 이들은 홍삼으로 제조된 후 내공 내백 등이 혼재되어 나타났으며 정상수삼이 정상홍삼으로 나타난 경우는 5본이었고, 내백은 5본, 내공은 6본으로 조사되었다. 또한 수삼에서 4본은 썩은 부위가 포함되어있는 수삼이었는데 홍삼으로 제조되었을 때 3본은 내백으로 되었고 1 본은 수삼에서 썩은 부위가 1/4정도로 미미해서 홍삼 제조시 정상으로 나타났다. 일반적으로 홍삼 제조시 내공의 발생은 제조공정에서 나타나는 경우가 많으며, 내백의 경우는 홍삼으로 가공되면서 발생하는 경우가 있고, 인삼이 성장될 때 부분적인 영양상태의 불충분이나 기후 등에 따른 영향을 받을 수 있기 때문에 앞으로 이에 대한 많은 연구가 이루어져야할 것으로 판단된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.53-60
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• 2010

In constructing ILM(Incremental Launching Method) bridges, a launching nose is generally used in order to absorb temporary stress occurring during launching. The sectional forces of superstructure of ILM bridges, which occurs during launching, varies significantly according to the length, weight and stiffness of the launching nose. Thus in order to guarantee the safety of section of ILM bridges, the change of stress according to interaction behavior between launching nose and superstructure should be considered. However, the span division and span length are often decided based on previous cases in practice. It makes the design sections of launching nose are similar in spite of different projects. The designer's anxiety to optimize the launching nose to affect the optimum design of superstructure is also weak. In this study, an design formular to optimize the nose is proposed by using the analysis formular of nose-deck interaction and the design level of ILM bridges constructed on 00 Expressway is examined. According to the result of this study, the proposed design formulas are expected to make a significant contribution to section design that is economically efficient and at the same time guarantees the safety of the superstructure and launching noses of ILM bridges regardless of span length.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.549-559
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• 2005

A railway bridge with a double composite section is proposed to enhance the structural performance of existing two-girder bridges because the governing design parameter of railway bridges is the flexural stiffness. The concrete deck in negative moment regions is neglected in the design of continuous composite bridges assuming the concrete slab has no resistance to tension. Therefore, the flexural stiffness of the composite section in the negative moment region is reduced resulting in the increase of the depth of the steel section. In order to resolve this disadvantage, several methods are suggested and the double composite section is one of the excellent solutions for extending the span length and increasing the flexural stiffness. In this study, push-out tests on lying studs and mixed stud shear connection with lying and vertical studs were performed to investigate the behavior of the shear connection in the double composite section. Static strength of the shear connection was evaluated through the test results and numerical analyses.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.194-202
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• 2006

In the present study, stiffness prediction methodologies for flat-plate structures were evaluated in comparison with the experimental results on the full-scale slab-column connections of flat-plate structures. The methodologies are as follows: the methodology proposed by Jacob S. Grossman and the methodology proposed by Choi & Song. The former does not predict the stiffness change of the slab-column connection due to the change in the column section shape and the latter overestimates the stiffness when edge length of the column section in the loading direction is long. In the present study, the equation to calculate the effective width of slabs was modified to reflect the effect of the change in the column section shape.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.99-107
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• 2018

The objective of the present study is to propose a reliable shape of supplementary V-ties in the section jacketing approach for seismic strengthening of reinforced concrete columns. A total of 24 pull-out specimens were prepared. The test parameters selected with regard to bond strength of V-ties were the shape of V-ties, embedment length of V-tie legs, and compressive strength of concrete. The measured bond strength of V-ties with different shapes were compared with that of the conventional V-ties and predictions using CEB-FIP equation. Ultimately, V-ties with pressed end-details at their legs could be recommended for the supplementary lateral reinforcement of strengthening columns with jacketing thickness less than the embedment length [= max (75mm, $6d_b$)] of conventional V-ties, where $d_b$ is the diameter of the reinforcing bar used for V-ties.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.335-344
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• 2004

A general composite section of precast and cast-in-place concrete with prestressed and nonprestressed reinforcements was analyzed to calculate residual stresses and loss of prestressing force caused by internal constraints of concrete long-term deformation. From the analytical results, equations to design additional prestressing force and to evaluate resistant moment of the composite section were proposed. The equations shows that the additional prestressing force can be over-estimated if the loss rate of the first prestressing force is over-estimated from the lumped sum of a design code. The analytical procedure with the proposed equations has been applied to a composite section using the AASHTO Type 5 girder. The loss rates of the additional prestressing force appling to the precast concrete girder was less than those appling to the composite girder. However, the resistant moment of the additional prestressing force on the composite girder was much larger than that on the precast concrete girder. The additional prestressing force appling to the composite section was very effective for strengthening of the prestressed concrete composite girder.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.121-129
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• 2010

The purpose of this study is to present the resonable guideline of asphalt concrete pavements in apartment complex. To achieve this purpose was performed review of domestic and foreign guidelines, investigation of main distresses of asphalt concrete pavement, and structural analysis for the investigated cross-sections of the pavements in apartment complex. According to results of structural analysis, this study presented the standard cross-section of the pavement with subbase of 20cm, asphalt base of 5cm, and surface of 5cm in apartment complex. In urban areas, traffic is generally opened after asphalt base course is placed because of civil complaint by dust. Surface course is placed after all of work are completed. Considering these conditions, this study also presented the standard cross-section of the pavement with subbase of 20cm, asphalt base of 7cm, and surface of 5cm for urban areas that expect civil complaints by dust.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.347-357
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• 2013

Recently, In recognition of outstanding structural performance the use of Concrete Filled steel Tube(CFT) columns has been increased. Research is ongoing that effective use of cross-sectional because steel strength development and rising prices. In this Lab, suggests new shape by Thin steel plates bent to be L-channel welded to form square steel tube to maximize efficiency of the cross section. In addition, since the rib placed at the center of the tube width acts as an anchor; higher load capacity of buckling is acceptable. we have developed New shape welded built-up square tube for broader usability which were bent to be L-shaped and thin Plate each unit member were welded. In order to apply the new shape built-up square columns, we predicted structure behavior, stress distribution with parameter Width thickness ratio. The experimental results presented in standards and even exceed the b/t of the rib anchors installed in the role due to exert enough strength and deformation to improve performance was favorable.