• Structural Engineering and Mechanics
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• 제61권5호
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• pp.593-603
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• 2017

A high-efficiency simplified modelling approach is proposed for investigating the nonlinear responses of reinforced concrete linings of shield tunnels. Material and geometric nonlinearities are considered in the analysis of the lining structures undergoing large deformation before ultimately losing the load-carrying capacity. A beam-spring element model is developed to capture the force-transfer mechanism between lining segments and radial joints. The developed model is validated by comparing analyzed results to experimental results of a single-ring lining structure under two loading conditions: the ground overloading and the lateral unloading respectively. The results show that the lining structure under the lateral unloading due to excavation on the both sides of the tunnel is more vulnerable compared to the case of ground overloading on the top of the tunnel. A parameter study is conducted and results indicate that the lateral pressure coefficient has the greatest influence on the behaviour of the lining structure.

• Steel and Composite Structures
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• 제35권1호
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• pp.29-41
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• 2020

Cross-beams of modern through truss bridges are connected to truss chord at its nodes and between them. It results in variable rotational end restraint for cross-beams, thus variable bending moment distribution. This feature is captured in three-dimensional modelling of through truss bridge structure. However, for preliminary design or rapid assessment of service load effects such technique of analysis may not be available. So an analytical method of assessment of rotational end restraint for cross-beam of through truss bridges was worked out. Two cases - nodal cross-beam and inter-nodal cross-beam - were analyzed. Flexural and torsional stiffness of truss members, flexural stiffness of deck members and axial stiffness of wind bracing members in the vicinity of the analyzed cross-beam were taken into account. The provision for reduced stiffness of the X-type wind bracing was made. Finally, general formula for assessment of rotational end restraint was given. Rotational end restraints for cross-beams of three railway through truss bridges were assessed basing on the analytical method and the finite element method (three-dimensional beam-element modelling). Results of both methods show good agreement. The analytical method is able to reflect effects of some structural irregularities. On the basis of the obtained results the general values of rotational end restraint for nodal and inter-nodal cross-beams of railway through truss bridges were suggested.

• 한국지반신소재학회논문집
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• 제10권4호
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• pp.105-112
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• 2011

본 논문에서는 지속하중이 작용하는 보강토 구조물의 시간의존적 장기거동에 관한 수치 모델링 기법을 다루었다. 먼저 Power Law 기반의 크리프 모델을 이용하여 지오그리드와 뒤채움흙의 크리프 거동의 모델링에 대한 적용성을 검토 하였으며 나아가 보강토 교대 구조물의 장기 거동에 대한 해석에 적용하였다. 그 결과 Power Law 기반의 크리프 모델은 지오그리드와 뒤채움흙으로 구성되는 보강토 교대 구조물에 지속하중 작용시 발생하는 크리프 변형을 적절히 모사할 수 있는 것으로 검토되었으며 크리프 변형이 발생할 수 있는 뒤채움흙을 사용하는 경우 교대 벽체 및 상판기초에 허용치를 초과하는 변위가 발생할 수 있는 것으로 검토되었다. 본 연구에서 얻어진 결과의 실무적 적용 방안에 대한 내용을 기술하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.241-244
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• 2006

Recently wind turbines become large, constructed as farms and going out to offshore. Different design approach from onshore is needed for offshore wind turbine. At this paper concept and preliminary design of an offshore wind turbine of 3MW rated power are performed. The concept design started from modelling of the generator and gearbox. With these modelling the optimum specifications was acquired. Integrated type of drive train is designed with all parts are mounted on the tower top as the offshore maintenance strategy. At the preliminary stage control system, power production algorithm and safety system are designed. Load calculation is also performed. The 3MW offshore wind turbine concept/preliminary design and the process of design are obtained as results.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.903-908
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• 2006

Building energy simulation has become a useful tool for predicting cooling, heating and air-conditioning loads for facilities. It is important to provide building energy performances feed back to the mechanical and electrical system operator and engineer for energy conservation and maintenance of building. From this research, we set up the typical weather data of location, basic description of building, geometric modelling data and the specification of Installed primary HVAC system for establishing the simulation model about energy consuming that take place in multipurpose building complex. The simulation tool of building energy - EnergyPlus (DOE and BLAST based simulation S/W), it has been used and accomplished calculations and analyses for evaluating the effect of the system types and operating condition of central HVAC plant on the building energy consumption. In this paper, we offer comparison and simultaneous results those involve electricity consumption pattern and amount between actual operation versus EnergyPlus simulation to the object building during summer season.

• Geomechanics and Engineering
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• 제27권5호
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• pp.481-495
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• 2021

This article assesses and estimates the progressive failure mechanism of complex pit-rest secondary toppling of slopes that are located within the vicinity of the Gas Flare Site of Refinery No. 4 in South Pars Special Zone (SPSZ), southwest Iran. The finite element numerical procedure based on the Shear Strength Reduction (SSR) technique has been employed for the stability analysis. In this regard, several step modelling stages that were conducted to evaluate the slope stability status revealed that the main instability was situated on the left-hand side (western) slope in the Flare Site. The toppling was related to the rock column-overburden system in relation to the overburden pressure on the rock columns which led to the progressive instability of the slope. This load transfer from the overburden has most probably led to the separation of the rock column and to its rotation downstream of the slope in the form of a complex pit-rest secondary toppling. According to the numerical modelling, it was determined that the Strength Reduction Factor (SRF) decreased substantially from 5.68 to less than 0.320 upon progressive failure. The estimated shear and normal stresses in the block columns ranged from 1.74 MPa to 8.46 MPa, and from 1.47 MPa to 16.8 MPa, respectively. In addition, the normal and shear displacements in the block columns ranged from 0.00609 m to 0.173 m and from 0.0109 m to 0.793 m, respectively.

• Structural Engineering and Mechanics
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• 제84권5호
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• pp.651-664
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• 2022

A precise prediction of the ultimate bond strength between rebar and surrounding concrete plays a major role in structural design, as it effects the load-carrying capacity and serviceability of a member significantly. In the present study, Gaussian models are employed for modelling bond strength of ribbed steel bars embedded in concrete. Gaussian models offer a non-parametric method based on Bayesian framework which is powerful, versatile, robust and accurate. Five different Gaussian models are explored in this paper-Gaussian Process (GP), Variational Heteroscedastic Gaussian Process (VHGP), Warped Gaussian Process (WGP), Sparse Spectrum Gaussian Process (SSGP), and Twin Gaussian Process (TGP). The effectiveness of the models is also evaluated in comparison to the numerous design formulae provided by the codes. The predictions from the Gaussian models are found to be closer to the experiments than those predicted using the design equations provided in various codes. The sensitivity of the models to various parameters, input feature space and sampling is also presented. It is found that GP, VHGP and SSGP are effective in prediction of the bond strength. For large data set, GP, VHGP, WGP and TGP can be computationally expensive. In such cases, SSGP can be utilized.

• Advances in nano research
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• 제13권4호
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• pp.351-368
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• 2022

Recently, promising structural technologies like multi-function, ultra-load bearing capacity and tailored structures have been put up for discussions. Finite Element (FE) modelling is probably the best-known option capable of treating these superior properties and multi-domain behavior structures. However, advanced materials such as Functionally Graded Material (FGM) and nanocomposites suffer from problems resulting from variable material properties, reinforcement aggregation and mesh generation. Motivated by these factors, this research proposes a unified shape function for FGM, nanocomposites, graded nanocomposites, in addition to traditional isotropic and orthotropic structural materials. It depends not only on element length but also on the beam's material properties and geometric characteristics. The systematic mathematical theory and FE formulations are based on the Timoshenko beam theory for beam structure. Furthermore, the introduced element achieves C1 degree of continuity. The model is proved to be convergent and free-off shear locking. Moreover, numerical results for static and free vibration analysis support the model accuracy and capabilities by validation with different references. The proposed technique overcomes the issue of continuous properties modelling of these promising materials without discarding older ones. Therefore, introduced benchmark improvements on the FE old concept could be extended to help the development of new software features to confront the rapid progress of structural materials.

• 조명전기설비학회논문지
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• 제21권3호
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• pp.62-68
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• 2007

최근 전력 전자 응용 기기의 사용증가로 비선형 특성 부하에 의한 고조파가 상당히 발생하고 있으며, 이에 의한 영향으로 배전시스템의 변압기 열화, 소자의 고장, 통신 간섭 등의 여러 가지 문제를 발생시키고 있다. 따라서 배전 시스템에서의 고조파 수준과 전달특성을 정확하게 분석하기 위하여 배전시스템의 효과적인 실측정과 모델링에 관한 연구가 필요한 실정이다. 본 논문에서는 고조파 관리기준 IEC61000-3-6 토대로 배전 시스템의 고조파 특성을 해석하기 위하여 공통 결합점(Point of Common Coupling : PCC)을 선택하였다. 실 배전 시스템의 PCC 지점에서 고조파 전압, 전류를 측정하여, 고조파 분포, 비선형 부하 성분 및 고조파 전압, 전류 왜형률 (Voltage/Current Total Harmonic Distortion: VTHD/ITHD)을 분석하였다. 또한 정상상태에서 고조파 임피던스, 전압, 전류을 해석을 통하여 실 배전시스템을 효과적이고 정확하게 모델링 되었을 확인하였다. 또한 고조파 전류원 발생시에 고조파 전압, 전류를 비교 분석하여 고조파 전달특성을 조사하였다.

• 한국지반공학회지:지반
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• 제12권5호
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• pp.127-136
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• 1996

초 경량재인 E.P.S(20~30kg/m3)를 성토재로 사용하여 부족한 지지력과 침하에 대한 안정 성을 확보하는 방법이 최근 많이 사용되고 있다. 국내에서는 1993년 인천의 연약지반상 교대 됫채움재로 이 공법이 처음 사용된 이래 점차 활용이 늘어나고 있는 실정이다. 그러나 아직까지 EPS를 성토 재료로 사용한 지반에서 EPS의 거동을 예측하기 위한 합리적인 수치해석 모델이 제시되어 있지 않고 일축압축강도 및 크리프시험 결과에 따른 설계강도만이 제안되어 있는 실정이다. 따라서 본 연구에서는 성토재료로 사용된 EPS의 수치해석 모델을 제시하기 위하여 성토재로 사용되는 여러 종류 밀도의 EPS에 대해 구속압을 변화시키면서 삼축압축시험을 실시하였다. 삼축압축시험 결과를 분석하여 EPS의 축방향 변형률-응력 관계와 이의 도함수 그리고 포아송비를 밀도와 구속압에 의한 함수식으로 나타낼 수 있었다. 이 관계로부터 EPS의 거동을 예측하기 위한 비선형모델을 제안하였다.