• 전기학회논문지P
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• 제61권4호
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• pp.180-185
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• 2012

Tidal power is one of new and renewable energy sources. The seawater is stored inside a tidal embankment built at the mouth of a river or bay, where tides ebb and flow. The water turbine-generators produce power by exploiting the gap in the water level between the water outside and inside the embankment. Tidal power plant is a large plant that is installed on the sea. And then, the facility's operations and a separate control system for monitoring and maintenance is required. However, this plant predictive control of building systems and technologies have been avoided the transfer of technology from advanced global companies. Accordingly, the control system for core technology development and localization is urgently needed. This paper presents modeling and simulation using by PSS/E about generator, governor, exciter, and power system stabilizer for control system in Sihwa tidal power plant to improve the efficiency and develope of core technology. And the dynamic characteristics of governor and exciter were analyzed.

• Steel and Composite Structures
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• 제32권1호
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• pp.67-77
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• 2019

Pushover analysis captures the behavior of a structure from fully elastic to collapse. In this analysis, the structure is subjected to increasing lateral load with constant gravity one. Neglecting the effects of the higher modes and the changes in the vibration characteristics during the nonlinear analysis are the main obstacles of the proposed lateral load patterns. To overcome these drawbacks, whereas some methods have been presented to achieve updated lateral load distribution, these methods are not precisely capable to predict the response of structures, precisely. In this study, a new method based on optimization procedure is developed to obtain a lateral load pattern for which the difference between the floor displacements of pushover and Nonlinear Dynamic Analyses (NDA) is minimal. For this purpose, an optimization problem is considered and the genetic algorithm is applied to calculate optimal lateral load pattern. Three special moment resisting steel frames with different dynamic characteristics are simulated and their optimal load patterns are derived. The floor displacements of these frames subjected to the proposed and conventional load patterns are acquired and the accuracy of them is evaluated via comparing with NDA responses. The outcomes reveal that the proposed lateral load distribution is more accurate than the previous ones.

• Steel and Composite Structures
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• 제37권1호
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• pp.99-115
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• 2020

This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO₂) subject to seismic load. In order to control the foundation smartly, a piezoelectric layer covered the foundation. The weight of the building by a column on the foundation is assumed with an external force in the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori-Tanaka law is utilized for calculating the equivalent mechanical characteristics of the concrete foundation. The Kevin-Voigt model is adopted to take into account the structural damping. The concrete structure is modeled by a thick plate and the governing equations are deduced using Hamilton's principle under the assumption of higher-order shear deformation theory (HSDT). The differential quadrature method (DQM) and the Newmark method are applied to obtain the seismic response. The effects of the applied voltage to the smart layer, agglomeration and volume percent of SiO₂ nanoparticles, damping of the structure, geometrical parameters and soil medium of the structure are assessed on the dynamic response. It has been demonstrated by the numerical results that by applying a negative voltage, the dynamic deflection is reduced significantly. Moreover, silica nanoparticles reduce the dynamic deflection of the concrete foundation.

• Earthquakes and Structures
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• 제16권6호
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• pp.655-664
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• 2019

Behavior factor of a structure plays a crucial role in designing and predicting the inelastic responses of it. Recently, irregular buildings have been interested in many designers. To design irregular structures, recognizing the inelastic behavior of them is necessary. The main objective of this study is to determine the behavior factor of irregular Reinforced Concrete Moment Resisting Frames (RCMRFs) via nonlinear Incremental Dynamic Analysis (IDA). To do so, first, several frames are designed according to the regulations of the Iranian national building code. Then the nonlinear incremental dynamic analysis is performed on these structures and the behavior factors are achieved. The acquired results are compared with those obtained using pushover analysis and it is shown that the behavior factors acquired from the nonlinear incremental dynamic analysis are somewhat larger than those obtained from pushover analysis. Eventually, two practical relations are proposed to predict the behavior factor of irregular RCMRFs. Since these relations are based on the simple characteristics of frames such as: irregularity indices, the height and fundamental period, the behavior factor of irregular RCMRFs can be achieved efficiently using these relations. The proposed relations are applied to design of four new irregular RCMRFs and the outcomes confirm the accuracy of the aforementioned relations.

• 한국강구조학회 논문집
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• 제22권5호
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• pp.445-453
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• 2010

최근 추진되는 노후화된 저층형 건물의 리모델링의 대부분이 국내기준인 KBC2005의 내진성능에 미치지 못하는 실정이다. 이에 보강을 통한 신축건물과 견줄 수 있는 성능확보에 대한 연구가 많이 이루어지고 있으나, 실제건물의 진동계측을 통해 보강효과를 검증하는 연구는 상대적으로 매우 미흡한 실정이다. 또한 실물 구조물에 대하여 파괴 직전까지의 큰 손상 후에 진동계측을 통한 동적특성에 대한 연구도 매우 미약한 실정이다. 따라서 본 연구는 3층 철근콘크리트조 건물에 강판벽을 보강한 후 엑츄에이터로 하중을 주어 건물에 손상을 준 후에 손상 전 후의 진동 계측을 통하여 동적특성을 파악하였다. 진동계측을 통하여 보강효과를 확인할 수 있었다. 또한 80mm의 수평변위를 준 결과 구조물의 파괴 직전 손상 전 후에 장변과 단변의 고유진동수는 각각 20.85%, 5.77% 감소하였고, 감쇠율은 각각 53.9%, 23.15% 감소하였다.

• Earthquakes and Structures
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• 제7권2호
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• pp.201-216
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• 2014

In this paper the vulnerability of the confined masonry buildings is evaluated analytically. The proposed approach includes the nonlinear dynamic analysis of the two-story confined masonry buildings with common plan as a reference structure. In this approach the damage level is calculated based on the probability of exceedance of loss vs a specified ground motion in the form of fragility curves. The fragility curves of confined masonry wall buildings are presented in two levels of limit states corresponding to elastic and maximum strength versus PGA based on analytical method. In this regard the randomness of parameters indicating the characteristics of the building structure as well as ground motion is considered as likely uncertainties. In order to develop the analytical fragility curves the proposed analytical models of confined masonry walls in a previous investigation of the authors, are used to specify the damage indices and responses of the structure. In order to obtain damage indices a series of pushover analyses are performed, and to identify the seismic demand a series of nonlinear dynamic analysis are conducted. Finally by considering various mechanical and geometric parameters of masonry walls and numerous accelerograms, the fragility curves with assuming a log normal distribution of data are derived based on capacity and demand of building structures in a probabilistic approach.

• Steel and Composite Structures
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• 제21권1호
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• pp.93-107
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• 2016

Seismic fragility analysis is a probabilistic decision-making framework which is widely implemented for evaluating vulnerability of a building under earthquake loading. It requires ingredient named probabilistic model and commonly developed using statistics requiring collecting data in large quantities. Preparation of such a data-base is often costly and time-consuming. Therefore, in this paper, by developing generic seismic drift demand model for regular-multi-story steel moment resisting frames is tried to present a novel application of the probabilistic decision-making analysis to practical purposes. To this end, a demand model which is a linear function of intensity measure in logarithmic space is developed to predict overall maximum inter-story drift. Next, the model is coupled with a set of regression-based equations which are capable of directly estimating unknown statistical characteristics of the model parameters.To explicitly address uncertainties arise from randomness and lack of knowledge, the Bayesian regression inference is employed, when these relations are developed. The developed demand model is then employed in a Seismic Fragility Analysis (SFA) for two designed building. The accuracy of the results is also assessed by comparison with the results directly obtained from Incremental Dynamic analysis.

• The Journal of Asian Finance, Economics and Business
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• 제6권3호
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• pp.41-53
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• 2019

Building a target capital structure is one of the most important decisions in corporate financial management. The purpose of this article is to identify the determinants of capital structure and adjustment mechanism toward the target leverage. The partial adjustment model was applied on a sample of 306 non-financial companies listed on Vietnam stock exchange market during the period of 2008-2017. By the fixed effect model estimation method, the research results have discovered the factors of growth opportunities, firm size, tangible fixed assets and firm's unique characteristics have a positive effect on the target capital structure of enterprises. Besides, profitability and dividend payment have a negative effect on the target capital structure of enterprises. Accordingly, the research results show that the average adjustment speed toward target leverage of the firms is 90.03%. Research results also demonstrate firms have higher or lower debt ratio than the target debt ratio, capital surplus or capital deficit also have an impact on the adjustment rate toward the target capital structure. The research results are consistent with the Dynamic Trade-off Theory. From this result, this article has provided policy implications for non-financial companies listed on Vietnam's stock market in building a reasonable target capital structure according to operating timeline to maximize enterprise value.

• 조명전기설비학회논문지
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• 제25권8호
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• pp.70-81
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• 2011

In this paper, a multi-agent control system for DC-coupled photovoltaic (PV), fuel cell (FC), ultracapacitor(UC) and battery hybrid power system is studied for commercial buildings & apartment buildings microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. A multi-agent system based-power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build the multi-agent control system with pragmatic design, and a dynamic model proposed for a PV/FC/UC/battery bank hybrid power generation system. A dynamic simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Stateflow. Simulation results are also presented to demonstrate the effectiveness of the proposed multi-agent control and management system for building microgrid.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.133-134
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• 2020

The equation of end bearing capacity is applied differently depending on the type of pile, construction method, and load characteristics considering the construction standards. The bearing capacity equation of the design standard is presented in various ways according to the design conditions such as construction method and ground condition, etc. but, It does not reflect the ground strength according to the SPT-N value of weathered rock. This study analyzed the trend of allowable tip bearing capacity by pile diameter through about 480 dynamic loading tests conducted for the construction/quality management of piles for the last 6 years since 2015. The equation for the ultimate end bearing capacity per unit area according to the SPT-N value is presented. The proposed formula of ultimate end bearing capacity per unit area can be applied in the range of 15,000kN/m2 to 30,000kN/m2. The proposed formula, which complements the existing formula, enables pile design and construction/quality management.