• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.180-189
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• 1994

An approximate method of normal coordinate idealization for use in nonlinear R /C frames has been developed. Normal coordinate apporaches have been used for nonlinear problems in the past, but they are not recerved wide acceptance because of the need for eigenvector computation in each time step. The proposed method circumvents the eigenvector recalculation problem by evaluating a limited number of sets of mode shapes in performing the dynamic analysis. Then some of the predetermined sets of eigenvectors are used in the nonlinear dynamic repeatedly. The method is applied to frame structures with ductile R /C elements. The plastic hinge zones are modeled with hysteres~s loops which evince degrading stiffness and pinching effects. Effxiencies and accuracies of the method for this application are presented.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.421-432
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• 2002

In this study the modal characteristics and responses of an asymmetric structure with added viscoelastic dampers were investigated for design parameters such as eccentricity of stiffness and added dampers, the loss factor of the damping materials used. For modal characteristics, variation of the quantities such as natural frequencies, modal damping ratios, modal participation factors, and dynamic amplification factors were observed, and displacements at flexible and stiff edges, and at center of mass were obtained. Based on the results, the problem of the optimum damper distribution to minimize the torsional effects was addressed, and the proposed method for optimum damper distribution was applied to a multi-story structure to verify the applicability Finally the effect of viscous and viscoelastic dampers were compared by varying the loss factor of the viscoelastic material.

• Composites Research
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• v.19 no.2
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• pp.13-19
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• 2006

In this paper, parametric study was carried out to design sandwich structures for EDM machines controlling stacking sequence, stacking thickness of composites and rib configuration. Sandwich structures which are dealt with in this paper are composed of fibre reinforced composite for skin material and foam or resin concrete for core materials. The sandwich column has cruciform rib to enhance bending stiffness of the structure and the bed has several vertical ribs to resist the normal forces and vibration. The design parameters such as rib thickness and stacking sequence were controlled to enhance the system robustness. Finite element analysis was also carried out to verify the variation of static and dynamic stiffness of the structures according to the variation of the parameters. Vibration tests were performed to verify the natural frequencies and damping ratios of the manufactured composite structures. The appropriate shape and configuration conditions for micro-EDM machine structures are proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.19-30
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• 2009

The primary objective of the present study was to attempt to quantify the effect of the existing codes for CFT composite section on initial section flexural stiffness, based on the measured vibration frequency of CFT truss girders. The formulae for the initial flexural stiffness of the composite sections in the different codes are compared with the free vibration test results. The results of the free vibration test on the CFT truss girders are in good agreement with the analysis results when used in ACI formulae. The free vibration analysis of CFT truss girders for different f/L ratios was conducted to determine how the natural frequency of the CFT truss girder is affected by different f/L ratios. The presence of the f/L ratios in CFT truss girders alters its frequencies of vibration because of the global stiffness of the CFT girders. The frequency in horizontal modes decreases as the f/L ratio increases. However, the frequency in vertical modes increases as the f/L ratio increases.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.13-22
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• 2001

지진하중을 받는 다경간 단순형교의 낙교방지대책으로 적용되는 cable restrainer를 적절하게 설계하기 위해서는 restrainer의 보강효과에 대한 분석이 우선적으로 이루어져야한다. 본 연구에서는 단순지지 다경간 교량시스템을 중심으로 restrainer로 보강된 교량의 보강효과와 다양한 교량의 영향 요소를 고려할 수 있는 단순화된 해석모형을 개발하였으며, 이를 바탕으로 대상교량의 인접 진동계간의 상대거리, 충돌력, 하부교각으로 전달되는 전단역과 휨모멘트의 변화 등의 동적거동특성을 조사하여 restrainer의 보강효과를 분석하였다. 또한, restrainer의 여유길이 변화, 강성변화, 그리고 restrainer 길이변화에 따른 응답특성을 분석하였다.

• Journal of the Korean Geotechnical Society
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• v.29 no.5
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• pp.5-17
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• 2013

This study investigates the effect of thermal stress on axial load and pile settlement of PHC energy piles. A series of numerical analyses were performed by controlling major influencing parameters such as pile arrangement, pile spacing, end-bearing condition, soil condition and pile cap stiffness. It is found that the characteristics of pile-load transfer are significantly affected by seasonal operation mode (i.e., cooling and heating) throughout the year. Also, the axial load under thermal loading increases with increasing the pile spacing. The settlement of the pile in sand is larger than that in clay because of the thermal stress generated. It is also found that thermal stress highly influences on the end-bearing pile, corner pile and rigidity of pile cap.

• 한국도로학회:학술대회논문집
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• 2010.03a
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• pp.255-260
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• 2010

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.1-11
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• 1993

Precast/Prestressed concrete segmental bridges with moderate range of span length normally have a constant section height for economic segment manufacturing. Inside sectional dimension is often controlled for design of non-prismatic section between supports when variable stiffness is required. It is usual, in the preliminary design stage, to adopt trial bridge sections by past experience or by approximately estimated member forces. Three bridge models of different member stiffness have been selected to investigate flexural stiffness effects on member forces for preliminary design stage. The selected bridge stiffness has been determined by the flexibility index from review of the practically usable sections.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.177.1-182
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• 2002

본 연구는 합성교량의 경우 브라켓이나 가로보에 사용되고 비합성교량의 경우 연결재로 사용되는 스랩앵커를 Push-Out Test를 하여 실험으로 얻은 특성을 실제 소수주형모델에 적용하여 FEM해석을 통하여 거동특성을 파악 하고자 한다. 일반적으로 전단연결재 실험의 경우 콘크리트 슬래브와 강재 주형 사이에 직접 길이 방향 전단력을 작용시킬 수 있을 뿐 아니라 실험의 편리함 때문에 주로 Push-out 실험이 많이 이용되고 있다. 본 실험에서는 BS-5400에 제시된 바에 근거하여 실험체를 제작하였다. 이 실험을 통하여 탄성구간에서의 강성(k) 값을 알아내어 3D FEM 해석에 적용한다. 이때 콘크리트 바닥판과 강재와의 연결을 축 방향으로는 특정한 강성 값을 넣을 수 있는 Joint Element를 사용하여 연결시키고, 1경간 단순지지와 2경간 연속교에 대하여 연구를 수행하는데, 1경간 단순지지의 경우에는 Joint Element에 여러 강성 값과 실험을 통해 얻은 강성 값을 적용하여 합성거동을 파악하고 강성 값에 따른 합성정도를 규명하고자 한다. 또한 2경간 연속교에서는 슬랩앵커의 강성 값을 적용하여 많이 문제시되고 있는 내부지점부에 슬랩앵커를 사용하였을 때 슬래브의 인장응력이 어떤 변화양상을 나타내는지 파악 하고자한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.67-74
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• 2010

A variation of temperature acting on a RC roof slab causes a change of stress in concrete since it expands during summer and is compressed during winter. This behavior repeats annually and makes an affection to the structural capacity of member for both serviceability and ultimate level. In this paper, a cyclic temperature loading variation is calculated by analyzing the weather data of Korea for 20 years. In addition, an experimental work is planned to find the long term effect of temperature variation. Six RC slab are made with same dimension. Test parameters are loading duration (10, 20, 30 year) and whether it has pre-damage or not. Observation of stiffness variations according to cyclic loading period shows that the serious stiffness drop happens after 10 year's cyclic loading at summer while after 30 year's loading at winter. From the fracture test about slabs damaged by long term cyclic loading, however, the capacity of member such as initial stiffness and maximum strength were not changed except yield strength according to the period of long term cyclic loading. The yield strength tends to decrease after 20 year's cyclic loading.