• 소성∙가공
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• 제7권1호
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• pp.49-58
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• 1998

In this paper the bending collapse characteristics of 6XXX series aluminum rectangular tubes were studied with a pure bending collapse test rig which could apply the pure bending moment without imposing additional shear and tensile forces. Under the pure bending moment, there occured three kinds of bending collapse modes-local buckling delayed buckling and tensile failure-depending on the a, b, t (depth width thickness) and material properties. Experimental results are compared with the results of finite element method and other methods.

• 산업기술연구
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• 제20권B호
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• pp.131-138
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• 2000

In this paper, we would like to develop the bending collapse specific equation of aluminum members which are usually used in light-weight vehicle or electromobiles. The result of the developed equation are compared with that of test and finite element methods as the moment-rotational angle curves. Three types of aluminum members are tested with the pure bending collapse test rig. PAM-CRASH and ABAQUS program are used for finite element analysis. As the result the developed bending collapse governing equation is accurate in estimating the yield moment and the maximum moment. Especially, in the case of the local buckling and the delayed buckling, the developed equation is better effective than F.E.M.

• 대한기계학회논문집A
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• 제28권4호
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• pp.402-409
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• 2004

The purpose of this study is to investigate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear three-dimensional finite element analyses were performed to obtain the collapse moment of elbow containing various wall thinning defects located at intrados and extrados under two loading modes (closing and opening modes) with internal pressure. From the results of analysis, the effect of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependence of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

• 대한조선학회논문집
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• 제28권1호
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• pp.117-124
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• 1991

본 논문에서는 편면 보강판의 압축 강도 해석 시, 유한 요소법의 비경제성을 극복하기 위하여, 붕괴 양식을 가정하고, 각 붕괴 양식에 대해 압축 강도를 구하였다. 최종 강도는 탄성 대변형 해석 곡선과 소성 붕괴를 가정하여 얻은 소성 해석 곡선과의 교점으로 택하였다. 기존의 연구와는 달리 소성 붕괴선의 형상을 변경시켜 최소의 강도 값을 주는 교점을 최종 강도로 택하였다. 최소 강비는 가정한 붕괴 양식의 교점으로 부터 얻어질 수 있다. 탄성 해석에서는 좌굴 파형을 가정하고, 보강재의 비대칭으로 인한 편심 모우멘트를 고려하였으며, 평형 조건식은 Rayleigh-Ritz법을 이용하여 유도하였다. 소성 해석 시에는 고성 붕괴선을 가정하여 소성 붕괴 조건식을 유도하였다. 좌굴과 최종 강도 계산 결과를 유한 요소법에 의한 결과와 비교한 결과, 양호한 일치를 보였다.

• Steel and Composite Structures
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• 제26권5호
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• pp.635-647
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• 2018

In order to improve the efficiency of the Reinforced Concrete, RC, structures against progressive collapse, this paper proposes a procedure using alternate path and specific local resistance method to resist progressive collapse in intermediate RC frame structures. Cap truss consists of multiple trusses above a suddenly removed structural element to restrain excessive collapse and provide an alternate path. Steel strut is used as a brace to resist compressive axial forces. It is similar to knee braces in the geometry, responsible for enhancing ductility and preventing shear force localization around the column. In this paper, column removals in the critical position at the first story of two 5 and 10-story regular buildings strengthened using steel strut or cap truss are studied. Based on nonlinear dynamic analysis results, steel strut can only decrease vertical displacement due to sudden removal of the column at the first story about 23%. Cap truss can reduce the average vertical displacement and column axial force transferred to adjacent columns for the studied buildings about 56% and 61%, respectively due to sudden removal of the column. In other words, using cap truss, the axial force in the removed column transfers through an alternate path to adjacent columns to prevent local or general failure or to delay the progressive collapse occurrence.

• Earthquakes and Structures
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• 제5권3호
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• pp.277-296
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• 2013

Margin of safety against potential of progressive collapse is among important features of a structural system. Often eccentricity in plan of a building causes concentration of damage, thus adversely affects its progressive collapse safety margin. In this paper the progressive collapse of symmetric and asymmetric 3-story reinforced concrete ordinary moment resisting frame buildings subjected to the earthquake ground motions are studied. The asymmetric buildings have 5%, 15% and 25% mass eccentricity. The distribution of the damage and spread of the collapse is investigated using nonlinear time history analyses. Results show that potential of the progressive collapse at both stiff and flexible edges of the buildings increases with increase in the level of asymmetry in buildings. It is also demonstrated that "drift" as a more easily available global response parameter is a good measure of the potential of progressive collapse rather than much difficult-to-calculate local response parameter of "number of collapse plastic hinges".

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.209-216
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• 2006

For evaluation of building performance, a nonlinear dynamic capacity of the building is a key parameter. In this study, an reinforced concrete special moment resisting frame building was chosen to study the process of determining the nonlinear dynamic capacity. The building, which was designed by IBC 2003 representing new codes, was composed of special moment resisting frames in the perimeter and internal frames inside the building. The capacity, which is inter-story drift capacity, consists of two categories, local and global collapses. Global collapse capacity was determined by incremental dynamic analysis. Local collapse capacity was determined by the same method except for utilizing damage index. In audition to this, it was also investigated that the effect of including internal frames designed by gravity load in the analysis. Results showed that the damage index is a useful tool for determining local collapse. Furthermore, including the internal frames with special frames in the analysis is very important in determining the capacity of a building so both must be considered at the same time.

• 대한기계학회논문집A
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• 제28권10호
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• pp.1483-1491
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• 2004

To assess the integrity of the pipeline is the most important problem to be solved first of all for prevention of any fracture accident of the pipeline. As a result of exerting such efforts, a number of plastic collapse assessment equations have been suggested, however, the scope of using or applying such assessment equations has not been exactly defined. In this study, the case that a surface crack existed in the circumferential direction in the external side of the natural gas pipeline and a bending load was applied to the pipeline was analytically identified as the most critical condition, and a plastic collapse assessment equation fur it was suggested. The flow stress of the API X65 linepipe was defined through the experiment conducted on SENT specimens. Also, a local assessing criterion of a 3-dimensional crack behavior considering not only the crack depth but also the crack length was suggested. Finally, a plastic collapse assessment equation for the API X65 linepipe was developed by performing the 3-dimensional finite element analysis.

• 한국분무공학회지
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• 제25권2호
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• pp.60-67
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• 2020

Despite its benefit in engine thermal efficiency, gasoline-direct-injection (GDI) engines generate substantial particulate matter (PM) emissions compared to conventional port-fuel-injection (PFI) engines. One of the reasons for this is that the spray collapse caused by the spray-to-spray interaction forms the locally rich fuel-air mixture and increases the fuel wall film. Previous studies have investigated the spray collapse phenomenon through the macroscopic observation of spray behavior using laser optical techniques, but it is somewhat difficult to understand the interaction between sprays that is initiated in the near-nozzle region within 10 mm from the nozzle exit. In this study, the spray structure, droplet size and velocity data were obtained using an X-ray imaging technique from the near-nozzle to the downstream of the spray to investigate the spray-to-spray interaction and discuss the effects of spray collapse on local droplet size and velocity distribution. It was found that as the ambient density increases, the spray collapse was promoted due to the intensified spray-to-spray interaction, thereby increasing the local droplet size and velocity from the near-nozzle region as a result of droplet collision/coalescence.

• 화약ㆍ발파
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• 제29권2호
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• pp.1-12
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• 2011

외부폭발, 화재, 충돌, 지진, 태풍과 같은 비정상 하중에 의한 고층빌딩의 연쇄붕괴(progressive collapse) 해석에 관련된 많은 연구가 진행되고 있다. 특히 그러나 실규모의 고층건물을 대상으로 한 손상 및 붕괴에 실험은 현실상 불가능한 실정이다. 본 연구에서는 구조물 발파해체분야에서 적용되는 ELS 소프트웨어를 이용하여 외부폭발에 의한 고층 RC 구조물의 국부손상 및 연쇄붕괴시뮬레이션을 수행하였다. 현관으로부터 1m, 2m, 5m, 10m, 15m 이격되어 폭약 1,500kg이 폭발한 것을 가정하여, 이격거리에 따른 국부손상과 이에 따른 연쇄붕괴현상을 파악하였다. 특히 기폭시나리오에 따라 구조물 지지부재의 일부를 제거하여 구조물의 붕괴를 유도하는 발파해체기법을 국부손상-연쇄붕괴 전이과정 연구에 적용하였다.