• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.681-693
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• 2007

Construction techniques for continuous steel bridges were applied to steel-concrete double composite box girder bridges. Concrete depth and length at the bottom of the steel box in the negative moment region were determined by plastic moment region and negative moment region of the double composite section, respectively. Construction methods, such as crane lifting method, free cantilever method, and incremental launching method were used for the analysis of the construction stage. Two cases of the construction phase were considered and analyzed for the stress resultant of double composite girders. The behavior of the nose-deck elastic system was examined by three-dimensionless parameters, such as the nose length, the unit weight of the launching nose, and the flexural stiffness of the nose. The adoption of the launching nose has become an effective solution in the incremental launching of steel-concrete double composite box girder bridges.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.118.1-118.1
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• 2016

포항가속기연구소 PLS-II 저장링에 설치 운용을 위한 타원편광 언듈레이터(EPU114)용 초고진공 진공 챔버는 전체를 기계가공 후 용접하여 제작하는 기존의 방식을 바꾸어 알루미늄 압출 공법을 적용한 진공 챔버의 개발과 본제품 제작을 완료하였다. 압출 공법을 이용한 초고진공용 진공 챔버 제작은 기계가공 및 용접비용의 절감과 동일 형상의 진공 챔버를 상대적으로 쉽게 대량 생산을 할 수 있는 장점이 있다. 알루미늄 압출형 초고진공 진공 챔버의 기계, 진공 특성을 달성하기 위하여 정밀금형 제작기술, 특수압출기술, 표면처리기술 등이 필수적이다. 본 발표에서는 초고진공 진공 챔버 개발을 위하여 적용된 압출 공법의 소개와 함께 압출 공법이 적용된 타원편광 언듈레이터(EPU114)진공 챔버의 제작, 초고진공 진공달성, 설치 등의 과정을 내용으로 한다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.450-453
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• 2011

압출공법(incremental launching method)은 교대 배후에 거더 제작장소를 설치하고, 콘크리트를 이어쳐서 교량거더를 제작하고, 이것을 잭(jack)으로 밀어내는 가설방법이다. 이 공법에 의해 시공되는 교량의 상부단면은 시공 중에 지간의 중앙부와 지점부에 일시적이나마 모두 위치하게 된다. 따라서 단면들은 자중에 의해 발생되는 최대 정모멘트와 최대 부모멘트, 그리고 최대 전단력을 모두 경험하게 되는 구조적 특성을 가지고 있다. 한편 거더의 캔틸레버 작용을 감소시키기 위하여 거더의 선단에 압출추진코(launching nose)를 부착시킨다. 상부단면에 발생하는 이 일시적인 응력의 크기는 압출추진코의 단면특성에 따라 달라진다. 본 논문에서는 압출추진코와 상부단면의 상호작용에 관한 해석식의 정확성을 유지하고, 활용도를 높이기 위해서 압출추진코를 유사등단면(강성;등단면, 중량;변단면)으로 가정하여 단순화된 해석식을 제안하였고, 압출추진코의 단면이 등단면으로 가정한 기존 해석식의 정확성을 향상시키기 위해서 다이아프램의 중량을 집중하중으로 치환시켜 변형된 등단면 해석식을 제안하였다. 그리고 제안된 2개의 해석식의 정확성과 활용성을 판단하기 위해 실제 ILM교량 설계자료들을 통해 전산구조해석 프로그램과, 기존 해석식들과 비교 분석 하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.404-407
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• 2009

ILM(incremental launching method) 교량공법은 품질확보에 효과적인 프리스트레스 콘크리트 교량공법으로 인정받고 있다. 이 공법에 의해 시공되는 교량의 상부단면은 시공 중에 지간의 중앙부와 지점부에 일시적이나마 모두 위치하게 된다. 앞선 연구에서 압출 중인 ILM 교량의 상부단면에 발생하는 단면력의 변화를 간편하게 예측할 수 있는 해석식을 개발하였다. 그리고 개발된 해석식을 이용하여 매개변수들의 변화에 따른 상호작용의 영향을 분석하여 많은 대안들이 검토되는 초기 설계단계에 유용한 설계식도 제안하였다. 본 논문에서는 압출중인 ILM 교량의 상부단면에 발생하는 단면력을 효과적으로 제어위해 유도된 해석식을 이용하여 현재 국내 공용중인 ILM 교량의 설계수준을 검토하였고, 상부구조의 최적설계를 위한 방안을 제시하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.1-10
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• 1992

Since the structural system of a prestressed concrete bridge erected by Incremental Launching Method is varying continuosly during construction, the main girder bears alternating stress resultants different from those under a service load condition. The magnitude of these stress resultants depends on span lengths, nose length and stiffness ratios between girder and nose. A parametric study is performed for various span lengths, nose lengths and stiffness ratios. In order to analyze structural systems varying at every launching step two programs are developed; a pre-processor which automatically produces a data file for each stage and a main-processor which can summarize the results of all stages. From the results, the relationships between optimum nose length and stiffness ratio are proposed for various span lengths.

• Journal of Korean Society of Steel Construction
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• v.28 no.1
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• pp.35-42
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• 2016

This paper presents the structural analysis of two-span structures constructed by incremental launching method to traverse the existing facilities. The structure with a relatively short launching span can not be secure the structural stability caused by excessive deflection and overturning prior to reaching the maximum strength, because the length of the other span is different or the rear structure is not continuous. In order to estimate the stability of the construction stages of deflection and the overturning, the structural analysis was carried out. The parameters of the analysis is launching span ratio of the launching nose and the upper structure, weight ratio and so on. From the analysis result, the effects of parameters were investigated and a deflection formula of the launching nose and the condition of the overturning of structure were proposed.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.729-734
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• 2015

This research developed a new deep-bore, cup-shape, large forging process by combining die forging and free forging methods. In the proposed process, a preform for cup-shape large forging is produced by die forging, and a product with a deep bore is finally manufactured using an open die forging method, which is generally produced using a backward extrusion process. Finite element analysis results showed a higher effective strain distribution with a smaller forging load using the proposed method compared to the backward extrusion method. The production of a prototype with good internal quality using a small press capacity verified the proposed method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.139-150
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• 2006

ILM(incremental launching method) bridge is one of the prestressed concrete bridge construction methods widely adopted owing to its effectiveness for the quality control. The sections of the launched superstructure pass every position of the bridge spans. This launching process causes the bridge sections to be experienced in the quite different stress states with the stress state occurred after construction completely. Due to the self weight of sections, particularly, the superstructure sections(deck) experience maximum positive and negative moment as well as maximum shear force during launching process. To minimize the temporarily caused sectional forces, launching nose is generally used in the construction method. Therefore, the magnitude of this sectional forces should be checked for the safety of super structure in construction and it is dependent on the structural characteristics of launching nose. In this study, the simplified formulas to analyze the sectional force occurred by the nose-deck interaction in ILM construction are developed. The considering parameters are the span length ratio, stiffness ratio and weight ratio between the launching nose and the super structure. In particular, the developed formulas can consider the tapered sectional shape of launching nose and the diaphragm wall in the superstructure. Additionally, the sensitivity analysis is performed to analyze the effects of nose-deck interaction according to the design parameters.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.496-504
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• 1998

The eccentric extrusion and bending process for the forming of the curved rectangular hollow tube is newly developed. Generally the bending process of hollow tube is the secondary process followed by the extrusion process of the hollow tube from the round billet. So many defects such as wrinkling and the difference of wall thickness can be happened during the secondary bending process. In order to avoid the defects the new process named as "the eccentric extrusion and bending process" is suggested and applied to the U-bending of rectangular hollow tube. In this paper the kinematically admissible velocity field between the dies surface and the internal plug boundary surface s developed for the curving velocity. By the using of this curving velocity field the curvature of extruded products can be calculated with the parameters such as eccentricity dies length friction constant aspect ratio.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.245-258
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• 2012

ILM(incremental launching method) is a way of construction, installing a girder producing spot behind the abutment, making the bridge girder infilled with concrete continuously and launching with using by jack. The superstructure of the bridge constructed by this method is temporarily located on the center of the span and the supporting points under construction. Therefore, the sections are structurally undergone maximum positive moment, maximum negative moment, and maximum shear force arising from self weight. On the other hand, launching nose is attached to the front of the girder to decrease the cantilever effect. The magnitude of this temporary stress creating on the upper section is dependent upon the launching nose's characteristics. This study has proposed an analysis formula simplified on the assumption that the launching nose section is a quasi-equivalent section(rigid; equivalent section, weight; tapered section) in order to ensure the accuracy of the analysis formula and improve its usage with reference to the interaction between the launching nose and the upper section; and a prismatic analysis formula modified by displacing a diaphragm's weight by a concentrated load in order to improve the accuracy of the existing analysis formula that assumes the launching nose section as the equivalent section. To judge the accuracy and usage of two analysis formulas proposed, we have compared and analyzed computational structural analysis programs and existing analysis formulas based on actual ILM bridge data. As a result, all of two reveal the superior accuracy and also their usage has been improved by the simplification of analysis formulas.