• 비파괴검사학회지
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• 제21권4호
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• pp.391-397
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• 2001

비균질 적층 구조물에서의 유도초음파 전파는 이론적 분산성에 기초하여 실험적으로 규명된다. 이는 입사각도와 주파수의 적절한 선택은 적층 구조물에서의 유도초음파 발생에 중요하나는 깃을 드러낸다. 이론적 분산성은 접착층 두께와 층 두께, 물성치에 크게 의존한다. 실험적으로 분산성의 변화를 관찰하므로 비균질 적층 구조물의 접착층 두께를 측정하는 것이 가능하였다.

• Steel and Composite Structures
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• 제46권6호
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• pp.823-837
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• 2023

This paper presents the seismic performance of seven beam-column joints with an eccentricity between beam depths under cyclic loadings. The failure modes of the panel zone were divided into two types. One was the shear force failure that appeared in the entire panel zone (SFEPZ), the other was the shear force failure that appeared in the partial panel zone (SFPPZ). Seven finite element models were established using multi-scale methods. Compared with the experimental specimens, the hysteretic loops exhibited a similar trend. The multi-scale models could accurately simulate the experimental results. Furthermore, the calculation formulas of yield and plastic shear capacity of unequal-depth joints with outer annular stiffener were proposed.

• 환경위생공학
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• 제14권4호
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• pp.41-49
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• 1999

The water treatment by was performed to remove VOC and organic substances in the multi-stage ozone contactor. Ozone is mainly utilized to change the chemical structures of organic substance, of which finally has the purpose to degrad them. The removal efficiency of VOC has 20~60% at the ozone concentration of 3 ppm, in case of trichloroethylene, its efficiency is reduced by 85% at the ozone contact time of 8 min. Design factors such as the number of stage, ozone concentration, zone contact time are determined for optimal treatment in the multi-stage contactor.

• Structural Engineering and Mechanics
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• 제48권6호
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• pp.775-789
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• 2013

The current paper proposes a boundary element formulation, applicable to 2-D and 3-D elastostatics problems using a unified approach for transformations of the domain integrals into boundary integrals. The method is applicable to linear problems encompassing both finite and infinite multi-region domains allowing non-vanishing body forces. Numerical results agree quite well with the analytical solutions; while the present method offers easy formulation with less numerical efforts in comparison to FEM or some BEM which need interior points to treat arbitrary body forces. It is demonstrated that the method has the potential to have profound impact on engineering design, notably in dam-foundation interaction.

• Steel and Composite Structures
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• 제17권4호
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• pp.387-403
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• 2014

This paper presents a high accuracy Finite Element approach for delamination modelling in laminated composite structures. This approach uses multi-layered shell element and cohesive zone modelling to handle the mechanical properties and damages characteristics of a laminated composite plate under low velocity impact. Both intralaminar and interlaminar failure modes, which are usually observed in laminated composite materials under impact loading, were addressed. The detail of modelling, energy absorption mechanisms, and comparison of simulation results with experimental test data were discussed in detail. The presented approach was applied for various models and simulation time was found remarkably inexpensive. In addition, the results were found to be in good agreement with the corresponding results of experimental data. Considering simulation time and results accuracy, this approach addresses an efficient technique for delamination modelling, and it could be followed by other researchers for damage analysis of laminated composite material structures subjected to dynamic impact loading.

• Steel and Composite Structures
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• 제18권6호
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• pp.1369-1389
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• 2015

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can't be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

• Journal of Ship and Ocean Technology
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• 제4권3호
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• pp.21-32
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• 2000

In the present paper, the sloshing flow in the liquid holds of a large tanker is simulated using a numerical method. In the fluid domain, the three-dimensional Navier-Stokes equation with free surface is solved using a finite difference method, and the realistic shapes of multi holds are modeled including the internal members. The time-history of the tank motion is obtained using a time-domain program for ship motion. In order to computer the impulsive pressures on internal structures, a concept of buffer zone is adopted near the tank ceiling during impact occurrence. This study demonstrates that the global fluid motion in the multi liquid holds of ships and FPSO's can be simulated using the numerical method and the corresponding local pressure can be predicted with reasonable accuracy.

• 한국해안·해양공학회논문집
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• 제23권2호
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• pp.147-153
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• 2011

연안역 파랑제어 구조물의 설계와 연안역 관리에 있어서 안전성문제 뿐만 아니라 환경문제는 가장 중요한 요인 중 하나이다. 본 연구에서는 파랑을 효율적으로 제어할 뿐만 아니라 연안역 보존에도 유리한 구조물로써 다원주 군파일을 제안하였다. 이 구조물의 침식방지효과를 파악하기위하여 수리모형실험을 수행하였다. 본 연구에서는 콘크리트를 사용한 기존의 파제제와 다원주 군파일을 이용한 구조물을 동일 평면배치 상에 두고 실험을 하여 침식방지효과를 분석하였다. 다원주 군파일 구조물을 설치했을 경우 구조물 양끝단에서의 침식현상은 줄어들었으며, 구조물 배후의 퇴적경향은 뚜렷하게 나타남을 확인할 수 있었다.

• Smart Structures and Systems
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• 제15권1호
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• pp.99-117
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• 2015

The Stonecutters Bridge (SCB) in Hong Kong is the third-longest cable-stayed bridge in the world with a main span stretching 1,018 m between two 298 m high single-leg tapering composite towers. A Wind and Structural Health Monitoring System (WASHMS) is being implemented on SCB by the Highways Department of The Hong Kong SAR Government, and the SCB-WASHMS is composed of more than 1,300 sensors in 15 types. In order to establish a linkage between structural health monitoring and maintenance management, a Structural Health Rating System (SHRS) with relevant rating tools and indices is devised. On the basis of a 3D space frame finite element model (FEM) of SCB and model updating, this paper presents the development of an SHR-oriented 3D multi-scale FEM for the purpose of load-resistance analysis and damage evaluation in structural element level, including modeling, refinement and validation of the multi-scale FEM. The refined 3D structural segments at deck and towers are established in critical segment positions corresponding to maximum cable forces. The components in the critical segment region are modeled as a full 3D FEM and fitted into the 3D space frame FEM. The boundary conditions between beam and shell elements are performed conforming to equivalent stiffness, effective mass and compatibility of deformation. The 3D multi-scale FEM is verified by the in-situ measured dynamic characteristics and static response. A good agreement between the FEM and measurement results indicates that the 3D multi-scale FEM is precise and efficient for WASHMS and SHRS of SCB. In addition, stress distribution and concentration of the critical segments in the 3D multi-scale FEM under temperature loads, static wind loads and equivalent seismic loads are investigated. Stress concentration elements under equivalent seismic loads exist in the anchor zone in steel/concrete beam and the anchor plate edge in steel anchor box of the towers.

• 한국가스학회지
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• 제16권4호
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• pp.16-22
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• 2012

용접기술의 발달과 더불어 기계, 교량, 선박 그리고 가스설비 등의 제작공정을 위하여 용접의 이용이 증가하고 있다. 따라서 그들의 용접 구조물 제작을 위하여 높은 생산성과 안전설계를 고려하는 용접 법을 개발하는 것이 요구되고 있다. 본 연구에서는 재료 두께, 용접층수, 하중 방향 그리고 토우부의 노치 반경과 관련하여 완전 용입 십자형 필릿 용접부의 피로강도 및 피로수명의 특성에 대하여 기초적으로 고찰하였다. 대부분의 피로파괴는 십자형 필릿 용접의 토우부에서 발생하였다. 피로강도 및 피로수명은 토우 부의 노치 반경과 플랭크 각에 의한 응력집중의 영향을 받고 있다. 토우부의 금속이 다층 용접에 의하여 어닐링 되고 확산 되었으며 그 결과 침상 페라이트 조직이 형성되어 피로강도와 피로수명을 향상시켰다.