• 한국안전학회지
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• 제21권2호
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• pp.89-97
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• 2006

Recently, experimental and theoretical studies about nonlinear behavior of large concrete structures are in progress. The purpose of this study is to describe the nonlinear behavior of a concrete specimen under compression using several plastic models and to choose the best plastic model for later use in numerical analyses of concrete structures. ABAQUS is a general-purpose FEM program and we tested all suitable embedded material models for concrete. To verify the effectiveness of nonlinear analyses, results were compared with uniaxial and triaxial compression test results.

• Structural Engineering and Mechanics
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• 제21권6호
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• pp.699-712
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• 2005

The response of a plate-column system having five-degree-of-freedom supported by an elastic foundation and subjected to static lateral load, harmonic ground motion and earthquake motion is studied. Two Winkler foundation models are assumed: a conventional model which supports compression and tension and a tensionless model which supports compression only. The governing equations of the problem are obtained, solved numerically and the results are presented in figures to demonstrate the behavior of the system for various values of the system parameters comparatively for the conventional and the tensionless Winkler foundation models.

• Computers and Concrete
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• 제1권1호
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• pp.77-98
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• 2004

This paper presents a numerical model for simulating the nonlinear response of reinforced concrete (RC) shear walls subject to cyclic loadings. The material behavior of cracked concrete is described by an orthotropic constitutive relation with tension-stiffening and compression softening effects defining equivalent uniaxial stress-strain relation in the axes of orthotropy. Especially in making analytical predictions for inelastic behaviors of RC walls under reversed cyclic loading, some influencing factors inducing the material nonlinearities have been considered. A simple hysteretic stress-strain relation of concrete, which crosses the tension-compression region, is defined. Modification of the hysteretic stress-strain relation of steel is also introduced to reflect a pinching effect depending on the shear span ratio and to represent an average stress distribution in a cracked RC element, respectively. To assess the applicability of the constitutive model for RC element, analytical results are compared with idealized shear panel and shear wall test results under monotonic and cyclic shear loadings.

• 한국정보처리학회논문지
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• 제6권10호
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• pp.2838-2844
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• 1999

The motion-based video segmentation provides a powerful method of video compression, because it defines a region with similar motion, and it makes video compression system to more efficiently describe motion video. In this paper, we propose the Modified Fuzzy Competitive Learning Algorithm (MFCLA) to improve the traditional K-menas clustering algorithm to implement the motion-based video segmentation efficiently. The segmented region is described with the affine model, which consists of only six parameters. This affine model was calculated with optical flow, describing the movements of pixels by frames. This method could be applied in the low bit rate video transmission, such as video conferencing system.

• Smart Structures and Systems
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• 제22권6호
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• pp.643-662
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• 2018

One of the methods for investigation of mechanical behavior of materials is numerical simulation. For simulation, its need to model behavior is close to real condition. PFC is one of the rock mechanics software that needs calibration for models simulation. The calibration was performed based on simulation of unconfined compression test and Brazilian test. Indeed the micro parameter of models change so that the UCS and Brazilian test results in numerical simulation be close to experimental one. In this paper, the effect of four micro parameters has been investigated on the uniaxial compression test and Brazilian test. These micro parameters are friction angle, Accumulation factor, expansion coefficient and disc distance. The results show that these micro parameters affect the failure pattern in UCS and Brazilian test. Also compressive strength and tensile strength are controlled by failure pattern.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.780-785
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• 2005

This paper aims to consider an overall benefit-duration optimization (OBDO) problem for the sake of maximizing owner's economic benefits, whilst considering influences of schedule compression incurred opportunity income on the profitability of a large-scale construction project. Unlike previous schedule optimization models and techniques that have focused on project duration or cost minimization, with greater weight on contractors' interests, OBDO facilitates owner's economic benefits through overall benefit-duration optimization. In this paper, the objective function of OBDO model is formulated. An example is illustrated to prove the feasibility and practicability of the overall benefit-duration optimization problem. The significance of employing OBDO model and future research work are also described.

• Steel and Composite Structures
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• 제47권1호
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• pp.121-134
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• 2023

This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.

• Composites Research
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• 제36권4호
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• pp.253-258
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• 2023

교통수단의 발전은 이동이 불편한 장애인들의 이동권 보장을 실현하였지만 차량사고시 발생할 수 있는 장애인 탑승객의 안전 향상은 일반 승객좌석에 비해 낮다고 할 수 있다. 특히 갑자기 발생할 수 있는 후방 추돌 사고의 경우 장애인 탑승객의 머리와 목 부상에 취약한 것이 현실이다. 이에 본 연구에서는 휠체어 운송 차량의 후방 추돌 시 차량내 장애인 탑승객의 머리와 목 상해지수 개선을 위해 headrest를 관상면으로 3등분한 multi-layer headrest foam이 제안되었다. 간이 모델을 통한 저속 후방 추돌 해석을 통해 foam의 다양한 압축 특성을 부여하기 위한 stress scale factor의 범위가 선정되었으며, 해당 범위를 parameter로 지정하여 GA최적화가 수행되었다. 최적화결과를 통해 layer의 압축 특성에 따른 HIC와 NIC간의 상간관계 분석이 이뤄졌으며, HIC는 Front layer, NIC는 Mid layer의 압축 특성에 가장 민감하게 반응하였고 Rear layer의 압축 특성은 가장 낮게 나타났다. Validation model에 일반headrest와 최적화된 multi-layer headrest를 각각 배치하여 저속 후방 추돌 sled test 해석을 수행하였으며, 일반headrest대비 multi-layer headrest에서의 HIC와 NIC가 낮게 도출되었다. multi-layer headrest에서의 압축 거동 역시 명확하게 나타나 multi-layer headrest가 일반headrest대비 머리와 목의 상해지수 개선에 효과적인 것이 검증되었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.707-708
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• 2012

• Earthquakes and Structures
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• 제14권3호
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• pp.273-283
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• 2018

Previous experimental researches indicate that reinforced concrete beam-column joints play an important role in the mechanical properties of moment resisting frame structures, so as to require proper design. In order to get better understanding of the beam-column joint performance, a rational model needs to be developed. Based on the former considerations, two typical models for calculating the shear carrying capacity of the beam-column joint including the inelastic reinforced concrete joint model and the softened strut-and-tie model are selected to be introduced and analyzed. After examining the applicability of two typical models mentioned earlier to interior beam-column joints, several adjustments are made to get better predicting of the test results. For the softened strut-and-tie model, four adjustments including modifications of the depth of the diagonal strut, the inclination angle of diagonal compression strut, the smeared stress of mild steel bars embedded in concrete, as well as the softening coefficient are made. While two adjustments for the inelastic reinforced concrete joint model including modifications of the confinement effect due to the column axial load and the correction coefficient for high concrete are made. It has been proved by test data that predicted results by the improved softened strut-and-tie model or the modified inelastic reinforced concrete joint model are consistent with the test data and conservative. Based on the test results, it is also not difficult to find that the improved beam-column joint model can be used to predict the joint carrying capacity and cracks development with sufficient accuracy.