• 한국정밀공학회지
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• 제19권12호
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• pp.127-133
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• 2002

The objective of this study is to investigate fatigue life and fatigue crack propagation behavior The experiment of fatigue life for MMC have been carried out for the stress ratio R＝0.1 at 20Hz. Fatigue lift limit of AC4CH alloy is about 70 ㎫ and Fatigue limit of MMC has been increment to 120 ㎫, therefore, fatigue limits of MMC is about 71 % higher than that of AC4CH alloy Crack propagation tests on half-size CT specimen of thickness 12.5mm were conducted by using sinusoidal waveform. The crack length was monitored by compliance method. Test conditions were at 0.1 and 0.05 of load ratio at 10Hz of loading frequency and test load was 2.3kN. The effects of stress ratio on the fatigue crack propagation behavior for MMC was discussed within the Paris law. As the results of this study, Fatigue crack propagation increased with increasing the load ratio.

• 한국정밀공학회지
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• 제17권4호
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• pp.163-172
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• 2000

The postbuckling behavior and progressive damage of composite laminated cylindrical shell under uniform external pressure were investigated by nonlinear finite element method programming. For the finite element analysis, nine-node 3-D degenerated elements were utilized, and arc-length method including line search was adopted for the iteration and load-increment along postbuckling equilibrium path. As results. buckling load, postbucking behavior, and progressive failure f3r various composite laminated cylindrical shells were discussed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.109-116
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• 2000

This paper presents the results of investigation on the effects of surface loading on the performance of soil-reinforced segmental retaining walls using the finite element method of analysis. A parametric study was performed by varying location of surface loading. The results of the analyses indicate that the increment of the reinforcement tensile load due to the presence of surface load may be significantly over-estimated when using the conventional approach. Furthermore, the external stability should be carefully examined when a surface loading is present just outside the reinforced soil zone. The implications of the findings from this study to current design approaches are discussed in detail.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.327-334
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• 2001

This paper presents a non-linear analysis procedure for plane frame structures by finite element formulation with assumptions of Timoshenko beam theory. Finite element displacement method based on Lagrangian formulation is used and two-noded and isoparametric line element is adopted to represent finite element model. The layered approach is used for the elasto-plastic analysis of the plane frame structures with rectangular and I cross sections. A load incremental method combined with the tangent stiffness and the initial stiffness methods for each load increment is used for the solution of non-linear equations. Numerical examples are presented to investigate the behavior and the accuracy of the elasto-plastic non-linear application and the results of this study are compared with other solutions using the concept of plastic hinge.

• 한국구조물진단유지관리공학회 논문집
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• 제11권5호
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• pp.123-134
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• 2007

본 논문은 기존 강합성 교량의 내하력 향상을 목적으로 외부 긴장재의 초기 긴장력 결정 방법을 제시하였다, 외부 긴장력은 콘크리트 슬래브 재시공 전과 후에 각각 적용하였다. 활하중에 의하여 발생하는 증가 프리스트레스력을 고려한 내하율식을 제안하여 긴장재 개수와 초기 긴장력의 결정 과정을 제시하였다. 기존 강합성 교량의 내하율 향상에 적용하여 그 타당성을 입증하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.681-688
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• 2000

This study presented the new method for evaluating the coefficient of consolidation by using inflection point method which was based on the fact that time factor, T corresponding to the inflection point of a semilogarithmic plot of a time curve is fixed and equals to T ＝ 0.405 at 70% consolidation. In the proposed method, the next load increment is applied as soon as the necessary time required to identify the inflection point. Thus, the coefficient of consolidation may be easily evaluated. The time required to complete the testing using this rapid consolidation method could be as low as 1.5-3 hours compared with 1 or 2 weeks in the case of the conventional consolidation test.

• 한국전산구조공학회논문집
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• 제23권5호
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• pp.525-533
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• 2010

Newmark방법과 같은 직접시간적분법은 시간증분 구간 사이에서 하중이 변하더라도 하중값을 그 시간 구간에서 일정한 하중으로 사용하기 때문에 일정진폭하중과 같은 연속적인 하중함수를 불연속적인 하중함수로 가정하고 수치계산을 수행한다. 따라서 이러한 하중함수의 근사에 따른 오차로 인하여 정확한 수치결과를 계산할 수 없다. 이에 반해, Gurtin의 변분식 에 기초한 유한요소방정식은 하중함수를 시간이력에 대하여 합성적분하여 계산한다. 따라서 시간증분 구간에서 하중이 변하더라도 연속적인 하중함수의 곡선을 따라 가면서 계산하기 때문에 신뢰할 수 있는 수치결과를 구할 수 있다. 본 논문에서는 1차원 막대의 자유단에서 일정진폭하중을 받는 문제를 수치해석하여 Gurtin방법이 Newmark방법 보다 일정진폭하중을 받는 문제에 더 적합한 방법임을 보인다. 또한, Gurtin방법이 일정한 하중을 받는 문제보다 일정진폭하중을 받는 문제에 더 효과적인 방법임을 보인다. Gurtin방법을 FORTRAN으로 프로그래밍하여 해석한 수치결과와 해석용 소프트웨어인 ADINA의 Newmark방법에 의한 수치결과를 비교하여 제시된 수치해의 정확성과 타당성을 검증한다.

• 한국지반공학회논문집
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• 제35권5호
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• pp.43-51
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• 2019

현재 국내에서는 비탈면의 안정성 확보를 위해 그라운드 앵커공법을 적용하고 있다. 그라운드 앵커는 시간이 지남에 따라 노후화 및 환경적 영향에 의한 부식, 릴렉세이션, 크립 등으로 긴장력 감소현상이 발생하며, 이로 인해 앵커의 긴장력은 설계앵커력 이하로 감소할 가능성을 내포하고 있다. 이에 국내에서는 정기적인 점검 시 또는 이상 징후가 발생한 앵커를 대상으로 리프트오프 시험을 수행하여 앵커의 잔존긴장력을 확인하고 있으나, 현재 국내 리프트오프 시험기준(국토해양부, 2010)은 수행 및 평가방법이 자세히 명시되어 있지 않은 실정이다. 이에 본 연구에서는 선행연구들을 바탕으로 하중 재하 제하 사이클, 하중 증분방법, 긴장재 긴장 방법 등을 고려하여 리프트오프 시험을 수행하였으며 현장에서의 시공성과 시간적 제한을 고려하여 효율적인 리프트오프 시험 및 평가방법 개선안을 제시하였다.

• 소성∙가공
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• 제11권1호
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• pp.84-89
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• 2002

This study is concerned with the analysis of the forming characteristics of radial-forward extrusion. Angle between radial and forward extrusion, gap height, and friction factor are considered as important design factors to affect forming characteristics in radial-forward extrusion. The rigid-plastic finite element method is adopted to analyze the effects of design factors on forming loads. The incremental rates of loads are nearly constant except the deformation zone from radial to forward extrusion. The smaller angle induces lesser force increment, therefore forming load increases as the angle increases. Maximum load also increases as gap-height decreases and friction factor increases.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.215-218
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• 1995

This paper presents an experimental study on the strength and deformation of concrete-filled circular steel short columns. Six specimens of concrete-filled circular short columns were tested under concentric compressive load. For comparsion, three specimens of circular steel short columns were also loaded to failure. The ultimate strength, ductility, and confinement mechanism of columns were compared. In the comparison, the effect of witch-thickness ratio and concrete compressive strength on the behavior of colimns were examed. As a result, the axial load verse axial average strain relationship of concrete-filled circular steel columns was very stable, because of interactions between the concrete and steel, the strength are 13% and 30% larger than the strength extimated by simply superimposed method of the concrete and steel. The ratio of the circumferential to longitudinal strain increment, both measured on the steel suface, was 0.28 up to the longitudinal strain of 0.1%, increases from 0.3 to 0.8 between the strain of 0.1% to 0.3%, and 0.8 beyond the strain of 0.3%