• Earthquakes and Structures
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• 제1권4호
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• pp.411-425
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• 2010

The effect of dead loads on dynamic responses of uniform elastic beams is examined by means of a governing equation which takes into account initial bending stress due to dead loads. First, the governing equation of beams which includes the effect of dead loads is briefly presented from the author's paper (Takabatake 1990). In the formulation the effect of dead loads is considered by strain energy produced by conservative initial stresses produced by the dead loads. Second, the effect of dead loads on dynamical responses produced by live loads in simply supported beams and clamped beams is confirmed by the results of numerical computations with the Galerkin method and Wilson-${\theta}$ method. It is shown that the dynamical responses, like dynamic deflections and bending moments produced by dynamic live loads, are decreased in a heavyweight beam when the effect of dead loads is included. Third, an approximate solution for dynamic deflections including the effect of dead loads is presented in closed-form. The proposed solution shows good in agreement with results of numerical computations with the Galerkin method and Wilson-${\theta}$ method. Finally, a method reflecting the effect of dead loads for dynamic responses of beams on the magnitude of live loads is presented by an example.

• 대한기계학회논문집B
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• 제37권12호
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• pp.1105-1112
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• 2013

본 연구에서는 난방설비 제어에 필요한 난방부하를 건물 특성계수를 사용하여 예측하는 방법을 제안하였고, 난방부하에 주된 영향을 미치는 시간별 온도와 일사량을 예측하는 방법을 제안하였다. 온도와 일사량은 기상청에서 예보되는 정보로부터 퍼지이론을 이용하여 예측하였고, 난방부하 예측을 위한 건물 특성계수는 EnergyPlus로부터 도출하였다. 본 연구에서 제안된 방법으로 얻어진 난방부하는 EnergyPlus의 결과와 잘 일치하였으며, 예측된 온도와 일사를 이용하여 예측한 난방부하의 변화 양상은 실측 기상데이터를 사용한 결과와 유사하였다.

• 한국주거학회논문집
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• 제23권2호
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• pp.107-114
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• 2012

Thermally Activated Building System(TABS) is a radiant heating and cooling system which uses structures as thermal storage by embedding pipes in a concrete slab. Using TABS as the cooling system in residential buildings can reduce energy consumption and peak loads. But the ratio of cooling loads handled by TABS is low in the residential buildings which are significantly influenced by outside condition because condensation and over-cooling may occur. However, recent interest on energy-saving buildings is increasing and new residential buildings are expected to be less influenced by outside with high-insulation and shading. In such residential buildings, the heating and cooling loads and the range of load changes reduce. So the ratio of loads handled by TABS can increase. Therefore, this research investigates the cooling performance and energy performance of TABS in the residential buildings with less influence from outside using the simulation.

• Wind and Structures
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• 제21권3호
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• pp.331-352
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• 2015

A series of wind tunnel tests were conducted on tapered super high-rise buildings with a square cross section by applying synchronous pressure measurement technology. The effects of global strategy of chamfered modification on aerodynamic loads and wind-induced responses were investigated. Moreover, local aerodynamic strategies of opening a ventilation slot in the corner of equipment and refuge floors were carried out. Results show that the global strategy of tapered elevation increased the vortex shedding frequency, but reduced vortex shedding energy, leading to reduction of across-wind aerodynamic loads and responses. Chamfered modification suppressed the across-wind vortex shedding effect on tapered buildings. Opening the ventilation slot further suppressed the strength of vortex shedding and reduced the residual energy related to vortex shedding in aerodynamic loads of chamfered buildings. Finally, the optimized locations of local aerodynamic strategies were suggested.

• 전기학회논문지
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• 제59권12호
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• pp.2157-2164
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• 2010

Microgrid is generally defined as cluster of small distributed generators, energy storages and loads. Through monitoring and coordinated control, microgrid can provide various benefits such as reduction of energy cost, peak shaving and power quality improvement. In design stage of microgrid, system dynamic simulation is necessary for optimizing of sizing and siting of DER(distributed energy resources). As number of the system components increases, simulation time will be longer. This problem can restrict optimal design. So we used simplified modeling on energy sources and average switching model on power converters to reduce simulation time. The effectiveness of this method is verified by applying to prototype microgrid system, which is consist of photovoltaic, wind power, diesel engine generators, battery energy storage system and loads installed in laboratory. Simulation by Matlab/Simulink and measurements on prototype microgrid show that the proposed method can reduce simulation time not sacrificing dynamic characteristics.

• 전기학회논문지
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• 제61권11호
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• pp.1617-1624
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• 2012

A DC power system has many loads with varied functions. Also, there may be large pulsed loads with short duty ratios which can affect the normal operation of other loads. In this paper, Voltage Bus Conditioner(VBC) without any current sensors is proposed to damp the bus voltage transients by parallel pulsed loads. The proposed control approach requires only one voltage sensor and carries out both the functions of damping the bus voltage transients and maintaining the level of energy stored. The proposed control technique has been implemented on a TMS320F2812 Digital Signal Processor(DSP). Simulated results by a Matlab Simulink and experimental results are presented which verify the control principles and demonstrate the practicalty of the approach.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1935-1943
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• 2014

In recent years, the induction machines are increasingly being used as self-excited induction generators (SEIG). This generator is especially widely employed for small-scale power plants driven by renewable energy sources. The application of power electronic components in the induction generator control (IGC) and the loading of SEIG using nonlinear loads will generate harmonic currents. This paper analyzes the propogation of harmonic currents on the SEIG with nonlinear loads. Transfer function method in the frequency domain is used to calculate the gain and phase angle of each harmonic current component which are generated by a nonlinear loads. Through the superposition approach, this method has also been used to analyze the propagation of harmonic currents from nonlinear load to the stator windings. The simulation for the propagation of harmonic currents for a 4 pole, 1.5 kW, 50Hz, 3.5A, Y-connected, rotor-cage SEIG with energy-saving lamps, have provided results almost the same with the experiment. It can prove that the validity of the proposed models and methods. The study results showed that the propagation of harmonic currents on the stator windings rejects high order harmonics and attenuates low order harmonics, consequently THDI diminish significantly on the stator windings.

• 생물환경조절학회지
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• 제26권4호
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• pp.258-267
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• 2017

The price competitiveness of photovoltaic system (PV system) has risen recently due to the growth of industries, however, it is rarely applied to the greenhouse compared to other renewable energy. In order to evaluate the application of PV system in the greenhouse, power generation and optimal installation area of PV panels should be analyzed. For this purpose, the prediction of the heating and cooling loads of the greenhouse is necessary at first. Therefore, periodic and maximum energy loads of a multi-span greenhouse were estimated using Building Energy Simulation(BES) and optimal installation area of PV panels was derived in this study. 5 parameter equivalent circuit model was applied to analyzed power generation of PV system under different installation angle and the optimal installation condition of the PV system was derived. As a result of the energy simulation, the average cooling load and heating load of the greenhouse were 627,516MJ and 1,652,050MJ respectively when the ventilation rate was $60AE{\cdot}hr^{-1}$. The highest electric power production of the PV system was generated when the installation angle was set to $30^{\circ}$. Also, adjustable PV system produced about 6% more electric power than the fixed PV system. Optimal installation area of the PV panels was derived with consideration of the estimated energy loads. As a result, optimal installation area of PV panels for fixed PV system and adjustable PV system were $521m^2$ and $494m^2$ respectively.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1520-1526
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• 2002

The Charpy and Izod impact tests are the most prevalent techniques used to characterize the effects of high impulse loads on ploymeric materials. An analysis method for rubber toughened PVC is suggested to evaluate critical dynamic strain energy release rates(G$\_$c/) from the Charpy impact energy measurements. An instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture energies and maximum critical loads. The dynamic stress intensity factor Kid was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.552-558
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• 2016

A control rod drive mechanism(CRDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod within a reactor core to control the reactivity of the core. The CRDM for Jordan Research and Training Reactor with 5MW power has been designed and fabricated based on the HANARO’s experience through KAERI and DAEWOO consortium. This paper describes the seismic test results to demonstrate the operability, the drop performance and the structural integrity of CRDM during or after seismic excitations. The seismic tests are carried out under 5 OBE and 1 SSE loads at three Test Rigs simulating the reactor structure and the pool top. From the tests, the CRDM is smoothly driven without a malfunction of stepping motor under OBE load. The pure drop time under OBE and SSE loads is measured as 1.169s and 1.855s to meet the design requirement. Also, it is found that the CRDM maintains the structural integrity without a change of the function and natural frequency before and after seismic loads.