• 한국안전학회지
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• 제27권6호
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• pp.115-121
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• 2012

This paper, being the second in a two-part series, presents the robust performance of the proposed design method which can enhance a reliability-based design optimization(RBDO) under the uncertainties of probabilistic models. The robust performances of the solutions obtained by the proposed method, described in the Part 1, are investigated through the parametric studies. A 10-bar truss example is considered, and the uncertain parameters include the number of data observed, and the variations of applied loadings and allowable stresses. The numerical results show that the proposed method can produce a consistent result despite of the large variations in the parameters. Especially, even with the relatively small data set, the analysis results show that the exact probabilistic model can be successfully predicted with optimized design sections. This consistency of estimating appropriate probability model is also observed in the case of the variations of other parameters, which verifies the robustness of the proposed method.

• Earthquakes and Structures
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• 제12권4호
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• pp.409-423
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• 2017

This paper proposes a quick and simplified method to describe masonry vaults in global seismic analyses of buildings. An equivalent macro-element constituted by a set of six trusses, two for each transverse, longitudinal and diagonal direction, is introduced. The equivalent trusses, whose stiffness is calculated by fully modeled vaults of different geometry, mechanical properties and boundary conditions, simulate the vault in both global analysis and local analysis, such as kinematic or rocking approaches. A parametric study was carried out to investigate the influence of geometrical characteristics and mechanical features on the equivalent stiffness values. The method was numerically validated by performing modal and transient analysis on a three naves-church in the elastic range. Vibration modes and displacement time-histories were compared showing satisfying agreement between the complete and the simplified models. This procedure is particularly useful in engineering practice because it allows to assess, in a simplified way, the effectiveness of strengthening interventions for reducing horizontal relative displacements between vault supports.

• Structural Engineering and Mechanics
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• 제15권2호
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• pp.181-198
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• 2003

Six large scale models of conventionally reinforced concrete coupling beams with span/depth ratios ranging from 1.17 to 2.00 were tested under monotonically applied shear loads to study their nonlinear behavior using a newly developed test method that maintained equal rotations at the two ends of the coupling beam specimen and allowed for local deformations at the beam-wall joints. By conducting the tests under displacement control, the post-peak behavior and complete load-deflection curves of the coupling beams were obtained for investigation. It was found that after the appearance of flexural and shear cracks, a deep coupling beam would gradually transform itself from an ordinary beam to a truss composed of diagonal concrete struts and longitudinal and transverse steel reinforcement bars. Moreover, in a deep coupling beam, the local deformations at the beam-wall joints could contribute significantly (up to the order of 50%) to the total deflection of the coupling beam, especially at the post-peak stage. Finally, although a coupling beam failing in shear would have a relatively low ductility ratio of only 5 or even lower, a coupling beam failing in flexure could have a relatively high ductility ratio of 10 or higher.

• Wind and Structures
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• 제29권3호
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• pp.177-194
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• 2019

While establishing adequate load paths in the light-frame wood structures is critical to maintain the overall structural integrity and avoid significant damage under extreme wind events, the understanding of the load paths is limited by the high redundant nature of this building type. The objective of the current study is to evaluate the system effects and investigate the load paths in the wood structures especially the older buildings for a better performance assessment of the existing building stock under high winds, which will provide guidance for building constructions in the future. This is done by developing building models with configurations that are suspicious to induce failure per post damage reconnaissance. The effect of each configuration to the structural integrity is evaluated by the first failure wind speed, amajor indicator beyond the linear to the nonlinear range. A 3D finite-element (FE) building model is adopted as a control case that is modeled using a validated methodology in a highly-detailed fashion where the nonlinearity of connections is explicitly simulated. This model is then altered systematically to analyze the effects of configuration variations in the model such as the gable end sheathing continuity and the gable end truss stiffness, etc. The resolution of the wind loads from scaled wind tunnel tests is also discussed by comparing the effects to wind loads derived from large-scale wind tests.

• Steel and Composite Structures
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• 제42권3호
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• pp.299-313
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• 2022

Steel-concrete-steel composite structures with bidirectional webs (SCSBWs) are used in large-scale projects and exhibit good mechanical performances and constructional efficiency. The shear behaviors of SCSBW deep beam members in key joints or in locations subjected to concentrated forces are of concern in design. To address this issue, experimental program is investigated to examine the deep-beam shear behaviors of SCSBWs, in which the cracking process and force transfer mechanism are revealed. Compared with the previously proposed truss model, it is found that a strut-and-tie model is more suitable for describing the shear mechanism of SCSBW deep beams with a short span and sparse transverse webs. According to the experimental analyses, a new model is proposed to predict the shear capacities of SCSBW deep beams. This model uses strut-and-tie concept and introduces web shear and dowel action to consider the coupled multi mechanisms. A stress decomposition method is used to distinguish the contributions of different shear-transferring paths. Based on case studies, a simplified model is further developed, and the explicit solution is derived for design efficiency. The proposed models are verified using experimental data, which are proven to have good accuracy and efficiency and to be suitable for practical application.

• Steel and Composite Structures
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• 제43권5호
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• pp.565-579
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• 2022

This study investigated the yielding capacity and performance of seismic dampers constructed with steel ring plates using numerical and analytical approaches. This study aims to provide an analytical relationship for estimating the yielding capacity and initial stiffness of steel ring dampers. Using plastic analysis and considering the mechanism of plastic hinge formation, a relation has been obtained for estimating the yielding capacity of steel ring dampers. Extensive parametric studies have been carried out using a nonlinear finite element method to examine the accuracy of the obtained analytical relationships. The parametric studies include investigating the influence of the length, thickness, and diameter of the ring of steel ring dampers. To this end, comprehensive verification studies are performed by comparing the numerical predictions with several reported experimental results to demonstrate the numerical method's reliability and accuracy. Comparison is made between the hysteresis curves, and failure modes predicted numerically or obtained/observed experimentally. Good agreement is observed between the numerical simulations and the analytical predictions for the yielding force and initial stiffness. The difference between the numerical models' ultimate tensile and compressive capacities was observed that average of about 22%, which stems from the performance of the ring-dampers in the tensile and compression zones. The results show that the steel ring-dampers are exhibited high energy dissipation capacity and ductility. The ductility parameters for steel ring-damper between values were 7.5 to 4.1.

• Current Optics and Photonics
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• 제7권4호
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• pp.419-427
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• 2023

The structural design of an optical-telescope assembly (OTA) for satellite laser ranging (SLR) is conducted in two steps. First, the results of a parametric study of the major design variables (e.g. dimension and shape) of the OTA part are explained, and the detailed structural design of the OTA is derived, considering the design requirements. Among the structural-shape concepts of various OTAs, the Serrurier truss concept is selected in this study, and the collimation of the telescope according to the design variables is extensively discussed. After generating finite-element models for different structural shapes, self-gravity analyses are performed. To minimize the deflection and tilt of the mirror and frame for the OTA under the limited design requirements, a parametric study is conducted according to design variables such as the shapes of the upper and lower struts and the spider vane. The structural features found in the parametric study are described. Finally, the OTA structure is designed in detail to maintain the optical alignment by balancing the gravity deflections of the upper and lower trusses using the optimal combination of the parameters. Additionally, thermal analysis of the optical telescope design is evaluated.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2409-2421
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• 2011

본 논문에서는 지진하중에 의한 1경간 1층 강재골조구조에 대한 하이브리드 실험을 수행하였다. 오른쪽 기둥 1개소와 상부의 트러스요소 또는 보요소는 수치해석모형으로, 왼쪽기둥 1개소는 물리적 부분구조모형으로 선택하여 요소의 성능 및 거동을 평가하였다. 실험은 1자유도 또는 3자유도만을 고려하여 실시간으로 하이브리드 실험을 수행하였으며, 이를 위한 제어 알고리즘은 MATLAB/Simulink를 이용한 방법과 OpenSees, OpenFresco와 xPCTarget를 이용하는 방법으로 나누어 수행하였다. 그리고 수치해석모형과 물리적 부분구조모형의 실시간 데이터 통신을 위하여 SCRAMNet을 사용하였다. 파이버단면을 이용한 구조해석이 가능한 OpenSees를 사용하여 수치해석을 실시하였으며, 실시간 하이브리드 실험결과를 이와 비교하였다. 단순한 구조모형을 이용하여 제어시스템의 유효성을 검증하고자 실시간 하이브리드 실험이 실시되었으며, 추후 심각한 비선형성을 갖거나 복잡한 구조물의 하이브리드 실험으로 확장할 예정이다.

• 한국전산구조공학회논문집
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• 제19권2호
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• pp.161-169
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• 2006

본 연구에서는 효과적인 인터넷 기반 구조해석 플랫폼을 개발하기 위하여 컴포넌트 모델을 제시하였다. 구조해석의 특성상 복잡한 알고리즘을 수행해야 하므로 다수 사용자에 대한 원활한 서비스를 위해 서버 연산 보다는 X-Internet을 이용한 클라이언트 연산을 실시하였다. 기존 상용 해석프로그램들의 사용자 편의적인 인터페이스에 부합되도록 Smart Client를 이용하여 윈도우 기반 인터페이스를 구축하였으며, 개발된 플랫폼의 재사용 및 확장성을 고려하여 컴포넌트 기반 프로그래밍을 함으로써 수정 및 변화에 능동적인 대처가 가능하게 하였다. 컴포넌트는 분할-단순화의 기법을 적용하여 전체 시스템을 표현하였고, 상위 컴포넌트와 하위 컴포넌트, 컴포넌트와 객체간의 관계에는 공통 인터페이스를 사용함으로써 라이브러리간의 연결을 명확히 구분하였다. 설계검토를 XML WebService를 사용하여 이기종 플렛폼과의 데이터 통신을 실시함으로써 차후의 통합 CAE에서의 데이터 교환의 기틀을 제시하였다. 2차원 트러스 구조물의 정적해석 및 설계검토를 수행하여 개발한 플랫폼의 효율성을 검증하였다.

• Structural Engineering and Mechanics
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• 제34권6호
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• pp.719-738
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• 2010

The aim of this paper concerns with the nonlinear analysis of cable-stayed bridges including the vibration effect of cable stays. Two models for the cable stay system are built up in the study. One is the OECS (one element cable system) model in which one single element per cable stay is used and the other is MECS (multi-elements cable system) model, where multi-elements per cable stay are used. A finite element computation procedure has been set up for the nonlinear analysis of such kind of structures. For shape finding of the cable-stayed bridge with MECS model, an efficient computation procedure is presented by using the two-loop iteration method (equilibrium iteration and shape iteration) with help of the catenary function method to discretize each single cable stay. After the convergent initial shape of the bridge is found, further analysis can then be performed. The structural behaviors of cable-stayed bridges influenced by the cable lateral motion will be examined here detailedly, such as the static deflection, the natural frequencies and modes, and the dynamic responses induced by seismic loading. The results show that the MECS model offers the real shape of cable stays in the initial shape, and all the natural frequencies and modes of the bridge including global modes and local modes. The global mode of the bridge consists of coupled girder, tower and cable stays motion and is a coupled mode, while the local mode exhibits only the motion of cable stays and is uncoupled with girder and tower. The OECS model can only offers global mode of tower and girder without any motion of cable stays, because each cable stay is represented by a single straight cable (or truss) element. In the nonlinear seismic analysis, only the MECS model can offer the lateral displacement response of cable stays and the axial force variation in cable stays. The responses of towers and girders of the bridge determined by both OECS- and MECS-models have no great difference.