• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1310-1316
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• 2008

Bi-layer and tri-layer structures of electro-active paper(EAPap) using conductive polyaniline(PANI) coating were investigated to improve bending displacement of cellulose EAPap. Two different counter ions, perchlorate($CIO_4^-$) and tetrafluoroborate($BF_4^-$), are used as dopant ions in the PANI processing. The actuation performances of hi-layer and tri-layer structure are evaluated in terms of tip displacement, blocked force, strain energy density and power output density. The actuation performance of the tri-layer actuator was better than the hi-layer structure, and the maximum displacement and blocked force of tri-layer $CIO_4^-$ doped-PANI-EAPap were 13.2 mm and 0.15 mN, respectively. Also the power output of the actuator is similar to the required power of biological muscle application.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1012-1017
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• 2008

In this study, We examine closely the capacity spectrum method which a kind of displacement-based method evaluated by displacement of structure as an alternative to the load-based analysis method. The displacement-based method can easily review the strength of structure, seismic performance, ductility. Seismic performance by using capacity spectrum method is divided into design response spectrum and capacity spectrum. We can diagram design response spectrum by deciding the design seismic factor depending on performance target, site classification, seismic level, return period as UBC-97. Capacity spectrum is a load-displacement curve obtained by Push-over analysis considering the geometric parameter and the material parameter. We execute the seismic performance evaluation by using the capacity spectrum method to reinforced concrete pier which has been seismic design. As a result, We confirmed that there is a yield point and a ultimate point close by design response spectrum of UBC-97.

• Structural Engineering and Mechanics
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• 제83권2호
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• pp.135-151
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• 2022

The generalized displacement method is a nonlinear solution scheme that follows the equilibrium path of the structure based on the development of the generalized displacement. This method traces the path uniformly with a constant amount of generalized displacement. In this article, we first develop higher-order generalized displacement methods based on multi-point techniques. According to the concept of generalized stiffness, a relation is proposed to adjust the generalized displacement during the path-following. This formulation provides the possibility to change the amount of generalized displacement along the path due to changes in generalized stiffness. We, then, introduce higher-order algorithms of variable generalized displacement method using multi-point methods. Finally, we demonstrate with numerical examples that the presented algorithms, including multi-point generalized displacement methods and multi-point variable generalized displacement methods, are capable of following the equilibrium path. A comparison with the arc length method, generalized displacement method, and multi-point arc-length methods illustrates that the adjustment of generalized displacement significantly reduces the number of steps during the path-following. We also demonstrate that the application of multi-point methods reduces the number of iterations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.281-284
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• 2008

구조물의 성능을 나타내는 성능평가에 있어 구조물의 재료 및 구조적 특성이 구조물의 성능에 미치는 영향을 분석하기 위해 고유치 해석과 비선형 정적해석을 수행하였다. 구조물의 성능에 영향을 주는 성능영향인자는 구조물의 재료적 특성과 관련하여 콘크리트 강도, 종방향 주철근, 횡구속 철근에 대하여, 구조적 특성과 관련하여 형상비, 축하중에 대하여 총 5가지로 정의하였다. 성능영향인자의 변화에 따른 분석 결과, 콘크리트 강도 증가에 따른 항복변위는 동일하지만 최대 기저전단력은 증가하였고 종방향 주철근 증가에 따른 항복변위와 최대 기저전단력은 모두 증가하였으며, 횡구속 철근 증가에 따른 항복변위와 최대 기저전단력의 변화량은 미비하였다. 형상비 증가에 따른 구조물의 항복변위는 증가하고, 최대 기저전단력은 감소하며, 축하중 증가에 따른 구조물의 항복변위와 최대 기저전단력은 감소하였다.

• Smart Structures and Systems
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• 제15권2호
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• pp.335-353
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• 2015

Previous long-term measurements of the Uldolmok tidal current power plant showed that the structure's natural frequencies fluctuate with a constant cycle-i.e., twice a day with changes in tidal height and tidal current velocity. This study aims to improve structural health monitoring (SHM) techniques for offshore structures under a harsh tidal environment like the Uldolmok Strait. In this study, lab-scale experiments on a simplified offshore structure as a lab-scale test structure were conducted in a circulating water channel to thoroughly investigate the causes of fluctuation of the natural frequencies and to validate the displacement estimation method using multimetric data fusion. To this end, the numerical study was additionally carried out on the simplified offshore structure with damage scenarios, and the corresponding change in the natural frequency was analyzed to support the experimental results. In conclusion, (1) the damage that occurred at the foundation resulted in a more significant change in natural frequencies compared with the effect of added mass; moreover, the structural system became nonlinear when the damage was severe; (2) the proposed damage index was able to indicate an approximate level of damage and the nonlinearity of the lab-scale test structure; (3) displacement estimation using data fusion was valid compared with the reference displacement using the vision-based method.

• Steel and Composite Structures
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• 제18권6호
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• pp.1557-1568
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• 2015

The nonlinear static analysis of structure, which is under the effect of lateral loads and provides the capacity curve of the structure, is defined as a push-over analysis. Ordinarily, by using base shear and the lateral displacement of target point, the capacity curve is obtained. The speed and ease of results interpretation in this method is more than that of the NRHA responses. In this study, the nonlinear static analysis is applied on the semi-rigid steel gabled frames. It should be noted that the members of this structure are analyzed as a prismatic beam-column element in two states of semi-rigid connections and supports. The gabled frame is modeled in the OpenSees software and analyzed based on the displacement control at the target point. The lateral displacement results, calculated in the top level of columns, are reported. Furthermore, responses of the structure are obtained for various support conditions and the rigidity of nodal connections. Ultimately, the effect of semi-rigid connections and supports on the capacity and the performance point of the structure are presented in separated graphs.

• Wind and Structures
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• 제31권4호
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• pp.373-380
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• 2020

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluid-structure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

• Smart Structures and Systems
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• 제6권4호
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• pp.363-372
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• 2010

Accurate peak response estimation of a seismically excited structure with frictional damping system (FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated the peak response of the structure with FDS by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In case that earthquake excitation is defined probabilistically, corresponding response of the structure with FDS becomes to have probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake excitation generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Coefficients of the proposed PDF are obtained by regression of the statistical distribution of the time history responses. Finally, the correlation between the resulting PDFs and statistical response distribution is investigated.

• 한국가스학회지
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• 제14권5호
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• pp.7-12
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• 2010

본 논문은 H빔과 강화 콘크리트에 의해 건설된 LNG 저장탱크의 외부탱크에 대한 응력 및 변위거동 안전성을 유한요소법으로 해석하였다. 외부탱크의 바닥면 콘크리트 구조물 중심부에 0.2g의 가진력을 가하였다. FEM 계산결과에 의하면, von Mises 최대응력은 돔루프 구조물의 가장자리 부근에서 발생하고, 최대변위 거동량은 돔루프의 중심부에서 형성되고 있음을 알 수 있다. 여기서 제시한 해석결과에 의하면, H빔의 개수가 증가할수록 집중응력과 변위거동량은 완만하게 증가한다는 사실이다. 이것은 강화 콘크리트 구조물의 강성도가 H빔의 강성도에 비해 대단히 높기 때문에 H빔의 개수가 돔루프의 안전성에 큰 영향을 미치지 못한다는 것이다. 따라서 0.2g 정도의 가진력을 가할 경우는 H빔의 자중량을 고려하여 개수를 60개 이하로 제한하는 것이 바람직하다.

• Smart Structures and Systems
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• 제21권2호
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• pp.207-223
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• 2018

In this inquisition, a passive damper namely Stockbridge Damper (SBD) has been introduced to the field of vibration control of Offshore Wind Turbine (OWT) to reduce the earthquake excitations. The dynamic responses of the structure have been analyzed for three recorded earthquakes and the responses have been assessed. To find an optimum SBD, the parameters of damper have been optimized using Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) and Particle Swarm Optimization (PSO). The influence of the design variables of SBD such as the diameter of messenger cable, the length of messenger cable and logarithmic decrement of the damping has been investigated through response variables such as maximum displacement, RMS displacement and frequency amplitude of structure under an artificially generated white noise. After that, the structure with optimized and non-optimized damper has been analyzed with under the same earthquakes. Moreover, the comparative results show that the structure with optimized damper is 11.78%, 18.71%, 11.6% and 7.77%, 7.01%, 10.23% more effective than the structure with non-optimized damper with respect to the displacement and frequency response under the earthquakes. The results show that the SBD can obviously affect the characteristics of the vibration of the OWT and RSM based on BBD and PSO approach can provide an optimum damper.