• 한국생산제조학회지
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• 제18권3호
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• pp.241-247
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• 2009

It is important to satisfy the requirements and standards for the protections of passengers in a car accident. There are lots of studies on the crushing energy absorption of a structure members in automobiles. We have studied to investigate collapse characteristics and moisture absorption movements of CFRP(Carbon Fiber Reinforced Plastics) hat shaped sectional members when CFRP laminates are under the hygrothermal environment. In particular, the absorbed energy, mean collapse load and deformation mode were analyzed for side members which absorbed most of the collision energy. Variation of CFRP interlaminar numbers is important to increase the energy absorption capability. Therefore we have made a static collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed.

• 한국생산제조학회지
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• 제18권5호
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• pp.507-513
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• 2009

It is important to satisfy the requirements and standards for the protections of passengers in a car accident. There are lots of studies on the crushing energy absorption of structure members in automobiles. We have investigated collapse characteristics and moisture absorption movements of CFRP(Carbon Fiber Reinforced Plastics) hat shaped sectional members when CFRP laminates are under the hygrothermal environment. The absorbed energy, mean collapse load and deformation mode were analyzed for side members which absorbed most of the collision energy. Therefore we have made a static collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed specimen.

• 한국전산구조공학회논문집
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• 제24권5호
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• pp.569-576
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• 2011

본 논문에서는 비선형정적해석 방법을 이용하여 기존의 연쇄붕괴 선형정적해석 절차에 수반되는 반복과정을 자동으로 수행하면서도 선형해석 결과와 동일한 결과를 나타내는 새로운 연쇄붕괴 해석절차를 제안하였다. 제안된 해석절차는 GSA 기준에 규정된 기존 선형정적해석법의 단점인 반복적 해석작업 및 그 과정에서 발생할 수 있는 시간과 오류의 가능성을 최소화하여 해석결과의 신뢰성을 확보가 있는 선형정적해석 절차이다. 제안된 해석절차를 검증하기 위하여 철근콘크리트 모멘트골조 및 철골 가새골조의 최하층 기둥부재를 제거한 후 기존 해석법과 제안 해석법을 적용하고 그 결과를 비교 분석하였다. 해석결과에 따르면 제안된 해석절차는 구조물의 붕괴여부의 판정 및 힌지 분포에 있어서 기존의 선형정적해석과 동일한 결과를 나타내었으며, 반복해석 과정이 불필요하므로 기존 해석법에 비하여 매우 짧은 시간에 해석을 수행할 수 있는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제48권2호
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• pp.207-220
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• 2013

In this study, the vulnerability of two existing asymmetric steel building frames to Progressive Collapse (PC) is assessed. The buildings have different frame systems, steel sections and number of stories (nine and six). An alternate path method (APM) with a linear static analysis (LS) is carried out according to General Services Administration (GSA) 2003 guidelines. The Demand Capacity Ratio (DCR) of each primary element (beams and columns) is given with its specific details for all frames. The results show that the nine-story building with a dual frame system (moment frame with bracing system) has a lower susceptibility and greater resistance to PC than the six-story building with a simple building frame system (gravity system with bracing system). Implementing built-up box-shaped sections for columns is a better choice than using built-up I-shaped sections because there is no weak axis for the box section.

• Steel and Composite Structures
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• 제30권3호
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• pp.253-269
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• 2019

This paper investigates the effects of the tensile catenary action on dynamic increase factor (DIF) in the nonlinear static analysis for progressive collapse of steel-frame buildings. Numerical analyses were performed to verify the accuracy of the empirical and analytical expressions proposed in the literature in cases where the catenary action is activated. For this purpose, nonlinear static and dynamic analyses of a series of steel moment frame buildings with a different number of spans and stories were carried out following the alternate path method. Different column removal scenarios were considered as separate load cases. The dynamic increase factor that approximately compensates for the dynamic effects in the nonlinear static analysis was selected so to match results from the nonlinear dynamic analysis. The study results showed that the many expressions in literature may not work in cases where the catenary stage is fully developed.

• Geomechanics and Engineering
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• 제13권2호
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• pp.301-318
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• 2017

Based on the existing research results, a three-dimensional failure mechanism of tunnel face was constructed. The dynamic seismic effect was taken into account on the basis of quasi-static method, and the nonlinear Mohr-Coulomb failure criterion was introduced into the limit analysis by using the tangent technique. The collapse pressure along with the failure scope of tunnel face was obtained through nonlinear limit analysis. Results show that nonlinear coefficient and initial cohesion have a significant impact on the collapse pressure and failure zone. However, horizontal seismic coefficient and vertical seismic proportional coefficient merely affect the collapse pressure and the location of failure surface. And their influences on the volume and height of failure mechanism are not obvious. By virtue of reliability theory, the influences of horizontal and vertical seismic forces on supporting pressure were discussed. Meanwhile, safety factors and supporting pressures with respect to 3 different safety levels are also obtained, which may provide references to seismic design of tunnels.

• 한국정밀공학회지
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• 제18권7호
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• pp.120-126
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• 2001

The widely used spot welded section members of vehicles are structures which absorb most of the energy in a front-end collision. In front-end collision, sufficiently absorbed in the front parts, the impact energy does not reach the passengers. Simultaneously, the frame gets less damaged. This structures have to be very stiff, but collapse progressively to absorb the kinetic energy as expected. In the view of stiffness, the double-hat shaped section member is stiffer than the hat shaped section member. In progress of collapse, the hat shaped section member is collapsing progressively, but the double-hat shaped section member does not due to stiffness. An analysis on the hat shaped section member was previously completed. This paper concerns the collapse characteristic of the double-hat shaped section member. In the program system presented in this study, an explicit finite element code, LS-DYNA3D is adopted for simulating complicate collapse behavior of double hat shaped section members with respect to spot weld pitches. And comparing with the results from the quasi-static and impact experiment, the simulation has been verified.

• 한국생산제조학회지
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• 제21권6호
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• pp.865-870
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• 2012

CFRP of the advanced composite materials as structure materials for vehicles has a widely application in lightweight structural materials of air planes, ships and automobiles because of high strength and stiffness compared with conventional materials. This study is to investigate the energy absorption characteristics and collapse mode of CFRP single and double hat shaped structural member under the axial static collapse test. The CFRP single and double hat shaped structural members stacked at different angles (${\pm}15^{\circ}$, ${\pm}45^{\circ}$, ${\pm}90^{\circ}$, $90^{\circ}/0^{\circ}$ and $0^{\circ}/90^{\circ}$ where the direction on $0^{\circ}$ coincides with the axis of the member). The axial static collapse tests were carried out for each member. Collapse mode and energy absorption characteristics of the each member were analyzed.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.647-660
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• 2018

The Incremental Dynamic Analysis (IDA) procedure is currently known as a robust tool for estimation of seismic collapse capacity. However, the procedure is time-consuming and requires significant computational efforts. Recently some simplified methods have been developed for rapid estimation of seismic collapse capacity using pushover analysis. However, a comparative review and assessment of these methods is necessary to point out their relative advantages and shortcomings, and to pave the way for their practical use. In this paper, four simplified pushover analysis-based methods are selected and applied on four regular RC intermediate moment-resisting frames with 3, 6, 9 and 12 stories. The accuracy and performance of the different simplified methods in estimating the median seismic collapse capacity are evaluated through comparisons with the results obtained from IDAs. The results show that reliable estimations of the summarized 50% fractile IDA curve are produced using SPO2IDA and MPA-based IDA methods; however, the accuracy of the results for 16% and 84% fractiles is relatively low. The method proposed by Shafei et al. appears to be the most simple and straightforward method which gives rise to good estimates of the median sidesway collapse capacity with minimum computational efforts.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.375-380
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• 2007

The goal of this paper is to develop a rational static method which consider efficiently the dynamic effect of the gravity load following sudden removal of element. For this goal this paper introduce the equivalent load for element stiffness which is a preceding research result and will develop equivalent static analysis which will be able to predict the maximum behavior considering dynamic effect. Some examples are provided to verify it. Equivalent static analysis is compared with the analysis method which is recommended by the GSA2003 guidelines and the time-history analysis which is the most accurate for dynamic behavior.