• Smart Structures and Systems
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• 제15권3호
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• pp.665-682
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• 2015

Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

• 한국전산구조공학회논문집
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• 제20권1호
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• pp.57-63
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• 2007

본 연구는 동하중의 영향을 받는 구조물의 효율적인 구조 해석 및 최적화 수행을 위해 임계 시간의 동하중을 등가 정하중으로 변환하는 방법을 제안한다. 동하중을 등가 정하중으로 변환하기 위해서는 적절한 자유도 선정이 중요하다. 그러나, 기존 방법에서는 자유도의 선정이 임의로 이루어져서 몇 개의 자유도에 과도한 정하중이 부과되거나, 구조물의 거동에 영향력이 없는 자유도들이 선정됨으로써 신뢰성이 떨어지는 결과를 제공하기도 한다. 본 연구에서는 2단계 축소기법과의 연동을 통해 중요 자유도를 선정하고, 선정된 자유도에 등가 정하중을 부과하는 방법을 제안하다. 주자유도는 구조물의 거동에 지배적인 영향력을 갖고 있으며, 손상 탐지나 시스템 검증에서도 중요한 의미를 갖는 자유도이다. 수치예제를 통해 선정된 자유도에 등가 정하중을 분포시킨 후 동하중하의 시간 응답과 비교하여 그 신뢰성을 확인한다.

• 대한기계학회논문집A
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• 제39권3호
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• pp.311-318
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• 2015

텔레비전의 운송 중 발생 가능한 낙하상황을 설정하고, 낙하충격으로부터 텔레비전을 보호할 수 있는 텔레비전 포장재의 최적설계를 수행하였다. 텔레비전 포장재의 최적설계는 등가정하중법을 이용하여 비선형동적응답 구조최적설계를 수행하였으며, 포장재의 최적설계 과정을 본 연구에서 제안하였다. 개념설계 단계에서 등가정하중법을 적용한 위상최적설계를 수행하였으며 상세설계 단계에서 가상모델을 사용한 응력등가정하중법을 이용하여 형상최적설계를 수행하였다. 응력등가정하중은 비선형동적응답 해석의 변위장뿐만 아니라 응력반응장과 동일한 선형해석반응장을 유발하는 선형정적하중이다. 즉, 비선형동적응답 해석에서의 응력반응장을 구조최적설계에서 제한조건을 설정할 수 있는 것이다. 실제 예제를 통해 등가정하중법을 적용한 최적설계 과정의 유용성을 검증하였다. 텔레비전 포장재 낙하 테스트는 LS-DYNA 를 사용하였으며 구조최적설계는 NASTRAN 을 사용하였다.

• 대한기계학회논문집A
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• 제38권6호
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• pp.619-627
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• 2014

본 논문은 등가정하중을 이용하여 제어시스템을 포함한 구조물의 설계를 위한 최적화 방법을 제안한다. 지난 연구는 구조물과 제어시스템 최적설계를 독립적으로 분리하여 수행하였고, 구조물과 제어시스템을 동시에 최적화하여도 제어시스템의 제어변수는 정상상태에서만 최적화하여 성능을 향상시켰다. 하지만 제어변수는 모든 시간영역에서 최적화해야 한다. 즉, 제어시스템의 해석은 과도상태에서 수행해야 한다. 본 연구에서는 새로운 등가정하중을 이용하여 제어변수를 포함하는 제어시스템 구조물의 최적설계를 위한 방법을 제시하였다. 등가정하중은 동적하중이 구조물에 작용할 때 발생하는 임의 시간에서의 변위장과 동일한 변위장을 만들어내는 정하중을 의미한다. 이렇게 계산된 등가정하중을 이용하여 설계영역에서 선형정적응답 최적설계를 진행한다. 몇 가지 예제를 통해 새로운 등가정하중을 적용한 동적응답 최적설계방법의 유용성을 확인하였다.

• 항공우주시스템공학회지
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• 제16권4호
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• pp.53-59
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• 2022

액체 로켓 엔진의 연소기, 터보펌프, 가스발생기, 밸브 등 주요 구성품 조립 부위에는 고압의 고온 가스와 극저온 유체의 기밀을 위해 스태틱 실이 사용된다. 스태틱 실은 조립 부위의 상대적 움직임이 없는 기밀 부위에 적용되는데, 극저온 및 고온 환경에서의 열팽창과 수축은 조립부에서 원치 않는 누설을 야기할 수 있기에 효과적인 스태틱 실 설계가 필수적이다. 조립성 개선을 위하여 비정렬 조립이 가능한 구면 플랜지가 체결부에 사용되는데, 구면 플랜지의 회전이 가능하도록 스태틱 실 역시 기능이 추가된 다. 본 연구에서는 스태틱 실 적용 주요 부위의 모사 플랜지 시험기를 제작하여 구조 해석과 함께 기밀시험을 수행하여 설계된 스태틱 실의 구조 건전성을 확인하였다.

• 한국항공운항학회지
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• 제23권1호
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• pp.24-29
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• 2015

In order to increase endurance flight efficiency of long endurance electric powered UAV, main wing of UAV should have high aspect ratio and low structural weight. Since a spar which consists of thin and slender structure for weight reduction can cause catastrophic failure during the flight, it is important to develop verification method of structural integrity of the spar with the light weight design. In this paper, process of structural analysis using non-linear finite element method was introduced for the verification of structural integrity of the spar. The static strength test of the spar was conducted to identify structural characteristic under the static load. Then, the experimental result of the spar was compared to the analytical result from the non-linear finite element analysis. It was found that the developed process of structural analysis could predict well the non-linear structural behavior of the spar under ultimate load.

• Structural Engineering and Mechanics
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• 제49권5호
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• pp.631-644
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• 2014

Seismic assessment and retrofitting of existing structure is a complicated work that typically requires more sophisticated analyses than performing a new design. Before the implementation of a Code for seismic design of buildings (GBJ 11-89), not enough attention has been paid on seismic performance of structures and a great part of the existing reinforced concrete structures built in China have been poorly designed according to the new version of the same code (GB 50011-2010). This paper presents a case study of seismic assessment of a non-seismically designed reinforced concrete building in China. The structural responses are evaluated using the nonlinear static procedure (the so-called pushover analysis), which requires its introduction within a process that allows the estimation of the demand, against which the capacity is then compared with. The capacity of all structural members can be determined following the design code. Based on the structural performance, suitable retrofitting strategies are selected and implemented to the existing system. The retrofitted structure is analyzed again to check the effectiveness of the rehabilitation. Different types of retrofitting strategy are discussed and classified according to their complexity and benefits. Finally, a proper intervention methodology is utilized to upgrade this typical low-rise non-ductile building.

• 한국안전학회지
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• 제25권3호
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• pp.91-99
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• 2010

In this study, the advanced numerical algorithm is developed which can performed the static and dynamic stochastic finite element analysis by considering the effect of uncertainties included in the member stiffness of steel cable-stayed bridges and seismic load. After conducting the linear and nonlinear initial shape analysis, the advanced numerical algorithm is the assessment tool which can performed structural the response analysis considering the static linearity and non-linearity of before or after induced intial tensile force, and examined the reliability assessment more efficiently. The verification of the developed numerical algorithm is evaluated by analyzing the regression analysis and coefficient of correlation using the direct monte carlo simulation. Also, the dynamic response characteristic and coefficient of variation of the steel cable-stayed bridge is calculated by considering the uncertainty of random variables using the developed numerical algorithm. In addition, the quantitative structural safety of the steel cable-stayed bridges is evaluated by conducting the reliability assessment based upon the dynamic stochastic finite element analysis result.

• Earthquakes and Structures
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• 제6권4호
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• pp.335-350
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• 2014

Historical masonry mosques are the most important structures of Islamic societies. To estimate the static and dynamic behavior of these historical structures, an examination of their restoration studies is very important. In this study, Kara Mustafa Pasha Mosque, which was built as a domed mosque by Kara Mustafa Pasha between 1666-1667 in Amasya, Turkey, has been analyzed. This study investigates the structural behavior and architectural features of the mosque. In order to determine specific mechanical properties, compression and three-point bending tests were conducted on materials, which have similar age and show similar properties as the examined mosque. Additionally, a three-dimensional finite element model of the mosque was developed and the structural responses were investigated through static and dynamic analyses. The results of the analyses were focused on the stresses and displacements. The experimental test results indicate that the construction materials have greatly retained their mechanical properties over the centuries. The obtained maximum compression and tensile stresses from the analyses have been determined as smaller than the materials' strengths. However, the stresses calculated from dynamic analysis might cause structural problems in terms of tensile stresses.

• 품질경영학회지
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• 제45권3호
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• pp.365-377
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• 2017

Purpose: In the A rotorcraft, the division of a long yaw control rod was studied to improve the heat treatment capability. The purpose of this study was to analyze whether division of yaw control rod affects quality reliability in the A rotorcraft and analyze whether it secured flight safety. Methods: The structural static test and the vibration durability test on the split shape of yaw control rod were carried out in order to examine and verify the existing structural analysis results. Results: Structural static test results showed that there were no cracks and vibration durability test results showed that there was no damage or breakage on the split yaw control rod. Conclusion: This study showed that the quality reliability was confirmed and thus the flight safety of the A rotorcraft was secured. And it is expected that the split technique of the yaw control rod will contribute to the development of the rotorcraft industry in the future.