• Computers and Concrete
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• 제6권3호
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• pp.187-202
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• 2009

This paper focuses on the flexural behavior of RC beams externally strengthened with Carbon Fiber Reinforced Polymers (CFRP) fabric. A non-linear finite element (FE) analysis strategy is proposed to support the beam flexural behavior experimental analysis. A development system (QUEBRA2D/FEMOOP programs) has been used to accomplish the numerical simulation. Appropriate constitutive models for concrete, rebars, CFRP and bond-slip interfaces have been implemented and adjusted to represent the composite system behavior. Interface and truss finite elements have been implemented (discrete and embedded approaches) for the numerical representation of rebars, interfaces and composites.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.536-539
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• 2004

This paper focues on the flexural behavior of RC beams externally reinforced using Carbon Fiber Reinforced Plastics plates. (CFRP) A non-linear finite element (FE) analysis is proposed in order to complete the experimental analysis of the flexural behaviour of the beams. This paper is a part of a complete program aiming to set up design formulate to predict the strength of CFRP strengthende beams, particularly when premature failure through plates-end shear or concrete cover delamination occurs. An elasto-plastic behaviour is assumed for reinforced concrete and interface elements are used to model the bond and slip.

• 한국음향학회지
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• 제15권2호
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• pp.33-39
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• 1996

비선형 건마찰 감쇠를 가진 외팔보의 강제진동 응답을 건마찰 감쇠기와 가진력의 위치변화에 대하여 미끄러진 변위와 힘레벨을 수치해석하였다. 구성모드의 분석은 비선형 감쇠를 가진 계를 해석하기 위해 구속조건과 Lagrange 승수에 기초를 두고 분석하였다. 외팔보의 진동분석 결과 건마찰 감쇠기가 부착된 단순 지지된 보(beam)에서 보여진 응답특성과 유사한 특성이 나타났다.

• Structural Engineering and Mechanics
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• 제21권3호
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• pp.295-313
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• 2005

This paper evaluates the effective width of composite steel beams with precast hollowcore slabs numerically using the finite element method. A parametric study, carried out on 27 beams with different steel cross sections, hollowcore unit depths and spans, is presented. The effective width of the slab is predicted for both the elastic and plastic ranges. 8-node three-dimensional solid elements are used to model the composite beam components. The material non-linearity of all the components is taken into consideration. The non-linear load-slip characteristics of the headed shear stud connectors are included in the analysis. The moment-deflection behaviour of the composite beams, the ultimate moment capacity and the modes of failure are also presented. Finally, the ultimate moment capacity of the beams evaluated using the present FE analysis was compared with the results calculated using the rigid - plastic method.

• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.337-342
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• 2013

이번 연구에서는 de Laval nozzle를 이용하여 다양한 유체해석 모델과 프로그램을 비교하여 그 성능을 파악하였다. de Laval nozzle은 eigenvalue에 의해 eigenvector값이 '-'와 '+'값을 동시에 갖는 물리현상을 내포하고 있으며, 압력조건에 따라 내부에서 Normal shock이 발생하게 된다. 이러한 non-linearity를 현재 우리가 주로 사용하고 있는 상용프로그램(cfx, fluent)과 EDISON, 직접 코딩한 프로그램(Matlab이용)이 얼마나 잘 표현하는지 알아보았다. 그 결과 Van Leer Vector Splitting을 이용할 경우 물리현상을 제일 잘 표현 하였다. 또한 난류 유동(Turbulence flow)을 고려하게 될 경우, Mesh가 Boundary layer를 표현할 정도로 정밀하지 못하다면 제대로 된 해석 결과를 얻을 수 없었으며, Wall 근처에서 Non-slip condition에 의해 Vortex가 형성되고, 이 Vortex가 Back flow를 유도하여 해가 수렴하는데 방해를 하게 됨을 알 수 있었다. 이를 방지하기 위해서는 유동이 잘 표현될 수 있도록 적절한 Computational environment를 형성해 주는 것이 매우 중요하다.

• Journal of Positioning, Navigation, and Timing
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• 제11권1호
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• pp.29-34
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• 2022

In this paper, we analyze the Non-Holonomic Constraint (NHC) satisfaction of Inertial Navigation System (INS) for vehicular navigation according to Inertial Measurement Unit (IMU) location. In INS-based vehicle navigation, NHC information is widely used to improve INS performance. That is, the error of the INS can be compensated under the condition that the velocity in the body coordinate system of the vehicle occurs only in the forward direction. In this case, the condition that the vehicle's wheels do not slip and the vehicle rotates with the center of the IMU must be satisfied. However, the rotation of the vehicle is rotated by the steering wheel which is controlled based on the Ackermann geometry, where the center of rotation of the vehicle exists outside the vehicle. Due to this, a phenomenon occurs that the NHC is not satisfied depending on the mounting position of the IMU. In this paper, we analyze this problem based on Ackermann geometry and prove the analysis result based on simulation.

• Steel and Composite Structures
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• 제13권3호
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• pp.239-258
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• 2012

In this paper, experimental investigations on high strength steel (HSS) stud connected steel-concrete composite (SCC) girders to understand the effect of shear connector density on their flexural behaviour is presented. SCC girder specimens were designed for three different shear capacities (100%, 85%, and 70%), by varying the number of stud connectors in the shear span. Three SCC girder specimens were tested under monotonic/quasi-static loading, while three similar girder specimens were subjected to non-reversal cyclic loading under simply supported end conditions. Details of casting the specimens, experimental set-up, and method of testing, instrumentation for the measurement of deflection, interface-slip and strain are discussed. It is found that SCC girder specimen designed for full shear capacity exhibits interface slip for loads beyond 25% of the ultimate load capacity. Specimens with lesser degree of shear connection show lower values of load at initiation of slip. Very good ductility is exhibited by all the HSS stud connected SCC girder specimens. It is observed that the ultimate moment of resistance as well as ductility gets reduced for HSS stud connected SCC girder with reduction in stud shear connector density. Efficiency factor indicating the effectiveness of high strength stud connectors in resisting interface forces is estimated to be 0.8 from the analysis. Failure mode is primarily flexure with fracturing of stud connectors and characterised by flexural cracking and crushing of concrete at top in the pure bending region. Local buckling in the top flange of steel beam was also observed at the loads near to failure, which is influenced by spacing of studs and top flange thickness of rolled steel section. One of the recommendations is that the ultimate load capacity can be limited to 1.5 times the plastic moment capacity of the section such that the post peak load reduction is kept within limits. Load-deflection behaviour for monotonic tests compared well with the envelope of load-deflection curves for cyclic tests. It is concluded from the experimental investigations that use of HSS studs will reduce their numbers for given loading, which is advantageous in case of long spans. Buckling of top flange of rolled section is observed at failure stage. Provision of lips in the top flange is suggested to avoid this buckling. This is possible in case of longer spans, where normally built-up sections are used.

• 한국구조물진단유지관리공학회 논문집
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• 제27권6호
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• pp.79-85
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• 2023

미끄럼방지포장은 도로의 부속물로서 도로 및 교통 특성으로 인해 미끄럼저항을 충분히 확보하지 못한 곳이나 도로선형의 변화가 심한 구간에서 포장의 미끄럼저항을 높여 자동차의 안전한 주행을 도모하기 위한 시설이라고 명시하고 있다. 특히, 눈, 비, 블랙아이스와 같은 기상 악천후 상황에서 미끄럼방지포장의 미끄럼저항성능은 도로교통 및 운전자의 안전에 큰 영향을 미친다. 하지만 현재 미끄럼저항성능을 측정하는 데 주로 사용되는 BPN은 시험 면적이 0.009 m²에 불과하여 전체 포장면에 대한 대표성을 나타내기 어렵기 때문에 미끄럼방지포장 유지관리를 위한 신뢰성 있는 미끄럼저항성능 평가방법이 필요한 실정이다. 본 연구에서는 지침 및 표준 조사를 통하여 BPN, SN, GN 시험의 미끄럼저항 성능평가 방법을 비교하고 현장 미끄럼저항 성능평가에 적용하고자 하였다. 또한, 미끄럼방지포장의 체계적인 유지관리를 위하여 미끄럼방지포장재 미끄럼저항 성능평가 Test-bed 및 실도로 실증 현장에 미끄럼저항성능이 다른 미끄럼방지포장을 설치하여 성능평가방법(BPN, SN, GN)별 미끄럼저항성능을 비교하였다. 실험결과, SN과 GN은 미끄럼저항성능이 비슷한 경향으로 나타났으며, GN은 BPN × 0.01 과 유사하게 도출되었다.

• 보건교육건강증진학회지
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• 제22권4호
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• pp.203-213
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• 2005

Purpose: To assess the environmental hazards of falling accident in the homes of the elderly. Method: 222 homes of the elderly were assessed by the home environmental Checklist from May to July in 2003. Results: The mean score of home environmental hazards for fall were 13.19 with the highest score being 49, ranging from 4 to 24. The bathroom was the most hazardous place in the home, porch came next bedroom, kitchen, living room and stair followed them. The floor surface such as finishes and non-skid mats was the most hazardous interior factor in the home, using bathroom came next furniture and illumination followed them. The floor surface such as finishes and non-skid mats in the bathroom, kitchen, living room and porch, illumination of bedroom and stair were the most prevalent hazards in the home of interior. Of the 49 potential hazards, bathroom grab bar was the most prevalent one with 89.9%, and non-skid rugs in the porch, bathroom and kitchen, safety of dinner table, the threshold and furniture of porch, and illumination of bedroom were prevalent more than half of the home under assessing. Men, living in the separate house or villa with stairs were in more hazardous environments. Conclusion: To reduce the potential hazards of fall accident in the home, improving hazards relating to floor surface such as slip resistance surface and mats is important specially those of the separate house or villa with stairs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.132-139
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• 2008

The blade vibration problem of bladed disk is the most critical subject to consider since it directly affects the stable performance of the engine as well as life of the engine. Especially, due to complicated vibration pattern of the bladed disk, more effort was required for vibration analysis and test. The research of measuring the vibration of the bladed disk, using NSMS(Non-intrusive stress measurement) instead of Aeromechanics testing method requiring slip ring or telemetry system with strain gauge, was successful. These testing can report the actual stresses seen on the blades; detect synchronous resonances that are the source of high cycle fatigue (HCF) in blades; measure individual blade mis-tuning and coupled resonances in bladed disks. In order to minimize the error being created due to heat expansion, the tip timing sensor is installed parallel to the blade trailing edge, yielding optimal result. Also, when working on finite element analysis, the whole bladed disk has gone through three-dimensional analysis, evaluating the family mode. The result of the analysis matched well with the test result.