• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.888-895
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• 2022

Lately, ocean nuclear power plants have attracted attention as one of diverse uses of nuclear power plants. Because ocean nuclear power plants are movable or transportable, it is necessary to analyze the thermal hydraulics in a moving frame of reference, and computer codes have been developed to predict thermal hydraulics in large moving systems. The purpose of this study is to incorporate a three dimensional dynamic motion model into the SPACE code (Safety and Performance Analysis CodE) so that the code is able to analyze thermal hydraulics in an ocean nuclear power plant. A rotation system that describes three-dimensional rotations about an arbitrary axis was implemented, and modifications were made to the one-dimensional momentum equations to reflect the rectilinear and rotational acceleration effects. To demonstrate the code's ability to solve a problem utilizing a rotational frame of reference, code calculations were conducted on various conceptual problems in the two-dimensional and three-dimensional pipeline loops. In particular, the code results for the three-dimensional pipeline loop with a tilted rotation axis agreed well with the multi-dimensional CFD results.

• Earthquakes and Structures
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• v.23 no.6
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• pp.549-580
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• 2022

This paper assesses the influences of modeling assumptions and uncertainties on the performance of the non-linear finite element (FE) model updating procedure and model clustering method. The results of a shaking table test on a four-story steel moment-resisting frame are employed for both calibrations and clustering of the FE models. In the first part, simple to detailed non-linear FE models of the test frame is calibrated to minimize the difference between the various data features of the models and the structure. To investigate the effect of the specified data feature, four of which include the acceleration, displacement, hysteretic energy, and instantaneous features of responses, have been considered. In the last part of the work, a model-based clustering approach to group models of a four-story frame with similar behavior is introduced to detect abnormal ones. The approach is a composition of property derivation, outlier removal based on k-Nearest neighbors, and a K-means clustering approach using specified data features. The clustering results showed correlations among similar models. Moreover, it also helped to detect the best strategy for modeling different structural components.

• Earthquakes and Structures
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• v.24 no.4
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• pp.247-258
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• 2023

Multiple pounding tuned rolling mass damper (MPTRMD) distributed in the cavity of voided slabs is proposed to passively control multi-story frame structures, which disperses the mass of the oscillator to multiple dampers so that the control device can be miniaturized without affecting the vibration control performance. The mechanism and the differential motion equations of the MPTRMD-controlled multi-degree-of-freedom system are derived based on the Lagrange principle. Afterward, this advanced RMD is applied to a simplified 20-floor steel frame to evaluate the seismic control performance in the numerical analysis. A four-storey frame structure equipped with MPTRMD is then taken for a shaking table test to verify its effectiveness of control performance. The pounding mechanism has been detailed studied numerically and experimentally as well. The numerical and experimental results show that the proposed damper is practically promising not only for its prominent control performance but also for its lightweight and space-saving. Additionally, the pounding mechanism influenced by the variable impact parameters exhibits a balance between the two effects of motional limitations and energy dissipation.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.463-480
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• 2023

The buckling-restrained braced frames with eccentric configurations (BRBF-Es) exhibit stable cyclic behavior and possess a high energy absorption capacity. Additionally, they offer architectural advantages for incorporating openings, much like Eccentrically Braced Frames (EBFs). However, studies have indicated that significant residual drifts occur in this system when subjected to earthquakes at the Maximum Considered Earthquake (MCE) hazard level. Consequently, in order to mitigate these residual drifts, it is recommended to employ self-centering systems alongside the BRBF-E system. In our current research, we propose the utilization of the Direct Displacement-Based Seismic Design method to determine the design base shear for a hybrid system that combines BRBF with an eccentric configuration and a self-centering frame. Furthermore, we present a methodology for designing the individual components of this composite system. To assess the effectiveness of this design approach, we designed 3-, 6-, and 9-story buildings equipped with the BRBF-E-SCF system and developed finite element models. These models were subjected to two sets of ground motions representing the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) seismic hazard levels. The results of our study reveal that although the combined system requires a higher amount of steel material compared to the BRBF-E system, it substantially reduces residual drift. Furthermore, the combined system demonstrates satisfactory performance in terms of story drift and ductility demand.

• Steel and Composite Structures
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• v.51 no.2
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• pp.173-183
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• 2024

This study investigates a new seismic retrofit system that utilizes rotational friction dampers and axial springs. The retrofit system involves a steel frame with rotational friction dampers (RFD) at beam-column joints and linear springs at the corners, providing energy dissipation and self-centering capabilities to existing structures. The axial spring acts as a self-centering mechanism that eliminates residual deformations, while the friction damper mitigates seismic damage. To evaluate the seismic performance of the proposed retrofit system, a series of cyclic loading tests were carried out on a steel beam-column subassembly equipped with the proposed devices. An analytical model was then developed to validate the experimental results. A performance point ratio (PPR) was presented to optimize the design parameters of the retrofit system, and a performance-based seismic design strategy was developed based on the PPR. The retrofit system's effectiveness and the presented performance-based design approach were evaluated through case study models, and the analysis results demonstrated that the developed retrofit system and the performance-based design procedure were effective in retrofitting structures for multi-level design objectives.

• Steel and Composite Structures
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• v.51 no.3
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• pp.289-304
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• 2024

The seismic performance of traditional steel frame-shear wall structures was significantly improved by the application of self-centering steel-reinforced concrete (SRC) wall-panel structures in the steel frames. This novel resilience functionality can rapidly restore the structure after an earthquake. The presented steel frame with steel-reinforced concrete self-centering wall-panel structures (SF-SCW) was validated, indicating its excellent seismic performance. The seismic design method based on bear capacity cannot correctly predict the elastic-plastic performance of the structure, especially certain weak floors that might be caused by a major fracture. A four-level seismic performance index, including intact function, continued utilization, life safety, and near-collapse, was established to achieve the ideal failure mode. The seismic design method, based on structural displacement, was proposed by considering performance objectives of the different seismic action levels. The pushover analysis of a six-floor SF-SCW structure was carried out under the proposed design method and the results showed that this six-floor structure could achieve the predicted failure mode.

• ETRI Journal
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• v.38 no.4
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• pp.735-745
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• 2016

The Paris agreement at the 21st Conference of the Parties (COP21) emphasizes the reduction of greenhouse gas emissions and increase in energy consumption in all areas. Thus, an important aspect is energy saving in buildings where the lighting is a major component of the electrical energy consumption. This paper proposes a building energy management system employing visible light communication (VLC) based on LED lighting. The proposed management system has key characteristics including personalization and localization by utilizing such VLC advantages as secure communication through light and location-information transmission. Considering the efficient implementation of an energy-consumption adjustment using LED luminaires, this paper adopts variable pulse position modulation (VPPM) as a VLC modulation scheme with simple controllability of the dimming level that is capable of providing a full dimming range. This paper analyzes the VPPM performances according to variable dimming for several schemes, and proposes a VPPM demodulation architecture based on dimming-factor acquisition, which can obtain an improved performance compared to a 2PPM-based scheme. In addition, the effect of a dimming-factor acquisition error is analyzed, and a frame format for minimizing this error effect is proposed.

• New & Renewable Energy
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• v.9 no.1
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• pp.60-68
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• 2013

In recent years, green house effect related natural disasters occur throughout the world. Carbon dioxide, mainly comes from the fossil fuel burning, is suspected to be the cause of green house effect. To reduce the emission of carbon dioxide, we need to find alternative energy resources such as photovoltaic energy. In this paper, the basic characteristics of wind force coefficient on a PV panel installed on the floating type PV energy generation system are investigated though the two-dimensional wind tunnel tests. Test variables included the angle of PV panel, direction of wind, number of rows of PV panel and attached or not attached frame. Based on the results obtained through the wind tunnel tests, it was found that the wind force coefficient can be used as a preliminary data in the design of the structure.

• Journal of the Korean Solar Energy Society
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• v.33 no.6
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• pp.54-61
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• 2013

This is study on the glazing performance of the apartment house to predict energy saving rate when the early design stage by calculating heating load. there are various factors of the window type in apartment building to save energy such as window's U-value, SC or SHGC, window wall ration, frame factor, sunshade coefficient and so on. In this study, we analyzed the heating load focused on the U-value, SC and window wall ration using variable heating degree days method for a small and middle size units $59m^2$, $84m^2$, respectively. Each cases were calculated heating load of the real models compared to standard model to predict energy saving rate. From those cases it was drew the conclusion that were window's U-value, SC and window wall ration for the small and middle size units to expect 10% energy saving rate at least.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.186-193
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• 2000

In this study the effect and applicability of viscoelastic dampers on the seismic reinforcement of steel framed structures are investigated in the context of the performance based design approach. The effect of the damper on dissipating the input seismic energy was investigated with a single degree of freedom system. For analysis models a five-story steel frame subjected to gravity load and a ten-story structure subjected to gravity and wind load were designed. the code-specified design spectrums were constructed for each soil type and performance objective and artificial ground excitation records to be used in the nonlinear time history analysis were generated based on the design spectrums. Interstory drift was adopted as the primary performance criterion. According to the analysis results both model structures turned out to satisfy the life safety performance level for most of the soil conditions except for the soft soil. It was also found that the seismic performance could be greatly enhanced by installing viscoelastic dampers on appropriate locations.