• Smart Structures and Systems
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• v.18 no.3
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• pp.449-470
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• 2016

Energy harvesting is an emerging technique that extracts energy from surrounding environments to power low-power devices. For example, it can potentially provide sustainable energy for wireless sensing networks (WSNs) or structural control systems in civil engineering applications. This paper presents a comprehensive study on harvesting energy from earthquake-induced structural vibrations, which is typically of low frequency, to power WSNs. A macroscale pendulum-type electromagnetic harvester (MPEH) is proposed, analyzed and experimentally validated. The presented predictive model describes output power dependence with mass, efficiency and the power spectral density of base acceleration, providing a simple tool to estimate harvested energy. A series of shaking table tests in which a single-storey steel frame model equipped with a MPEH has been carried out under earthquake excitations. Three types of energy harvesting circuits, namely, a resistor circuit, a standard energy harvesting circuit (SEHC) and a voltage-mode controlled buck-boost converter were used for comparative study. In ideal cases, i.e., resistor circuit cases, the maximum electric energy of 8.72 J was harvested with the efficiency of 35.3%. In practical cases, the maximum electric energy of 4.67 J was extracted via the buck-boost converter under the same conditions. The predictive model on output power and harvested energy has been validated by the test data.

• Earthquakes and Structures
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• v.10 no.1
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• pp.1-23
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• 2016

Steel plate shear walls (SPSWs) have been shown to be efficient lateral force-resisting systems, which are increasingly used in new and retrofit construction. These structural systems are designed with either stiffened and stocky or unstiffened and slender web plates based on disparate structural and economical considerations. Based on some limited reported studies, on the other hand, employment of low yield point (LYP) steel infill plates with extremely low yield strength, and high ductility as well as elongation properties is found to facilitate the design and improve the structural behavior and seismic performance of the SPSW systems. On this basis, this paper reports system-level investigations on the seismic response assessment of multi-story SPSW frames under the action of earthquake ground motions. The effectiveness of the strip model in representing the behaviors of SPSWs with different buckling and yielding properties is primarily verified. Subsequently, the structural and seismic performances of several code-designed and retrofitted SPSW frames with conventional and LYP steel infill plates are investigated through detailed modal and nonlinear time-history analyses. Evaluation of various seismic response parameters including drift, acceleration, base shear and moment, column axial load, and web-plate ductility demands, demonstrates the capabilities of SPSW systems in improving the seismic performance of structures and reveals various advantages of use of LYP steel material in seismic design and retrofit of SPSW systems, in particular, application of LYP steel infill plates of double thickness in seismic retrofit of conventional steel and code-designed SPSW frames.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.429-433
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• 2009

Since the "Low Carbon, Green Growth" as a social requirements is attracted public attention, the policies and investments of the railway which have been less estimated than road is re-considered. Since the starting the commercial service (2004. April), the KTX have been operated successfully while transport passengers over 100million for years. And also the project for development of KHST (Korea High Speed Train ; G7) had been accomplished with a good result, the first trainset of KTX-II which base on G7 project was manufactured and testing now. On the other hand, the world's technology of the high speed train is more faster, and changing to a distributed traction system. To catch up the world's leading technology, the HEMU(High-speed Electric Multiple Unit) project will secure new technology and aims to promote the technology of domestic high-speed train. The authors indicates the result of detail review such as a curve, slope of the track and electrical dead section of the catenary to test at 400kph and also the performance simulation of the developed rolling stock in this paper. As the result, the authors devise the test scenario to perform a maximum speed test (stability at max. speed, acceleration & deceleration etc) with the restricted conditions such as track length, track available time etc by considering above result.

• Geomechanics and Engineering
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• v.16 no.5
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• pp.527-538
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• 2018

The study on the performance of the nonlinear friction tuned mass dampers (FTMD) for the mitigation of the seismic responses of the structures is a topic that still inspires the efforts of researchers. The present paper aims to carry out a numerical study on the optimum tuning of TMD and FTMD parameters using a multi-objective particle swarm optimization (MOPSO) algorithm including soil-structure interaction (SSI) effects for seismic applications. Considering a 3-story structure, the performances of the optimized TMD and FTMD are compared with the uncontrolled structure for three types of soils and the fixed base state. The simulation results indicate that, unlike TMDs, optimum tuning of FTMD parameters for a large preselected mass ratio may not provide a best and optimum design. For low mass ratios, optimal selection of friction coefficient has an important key to enhance the performance of FTMDs. Consequently, a free parameter search of all FTMD parameters provides a better performance in comparison with considering a preselected mass ratio for FTMD in the optimum design stage of the FTMD. Furthermore, the SSI significant effects on the optimum design of the TMD and FTMD. The simulation results also show that the FTMD provides a better performance in reducing the maximum top floor displacement and acceleration of the building in different soil types. Moreover, the performance of the TMD and FTMD decrease with increasing soil softness, so that ignoring the SSI effects in the design process may give an incorrect and unrealistic estimation of their performance.

• Wind and Structures
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• v.34 no.6
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• pp.525-538
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• 2022

High-rise wooden pagodas generate large displacement responses under wind action. It is necessary and wise to reduce the wind loads and wind-induced responses on the architectural heritage using artificial plants, which do not damage ancient architecture and increase greenery. This study calculates and analyzes the wind loads and wind-induced responses on the Yingxian Wooden Pagoda, in China, using artificial plants via the finite element analysis (FEA). A three-dimensional wind-loading field was simulated using a wind tunnel test. Wind loads and wind-induced responses, including the displacement and acceleration of the pagoda with and without artificial plants, were analyzed. In addition, three types of tree arrangements were discussed and analyzed using the score method. The results revealed that artificial plants can effectively control wind loads and wind-induced displacements, but the wind-induced accelerations are enlarged to some extent during the process. The height of the tree significantly affected the shelter effects of the structure. The distance of trees from the pagoda and arrangement width of the tree had less influence on shelter effects. This study extends the understanding of the nondestructive method based on artificial plants, for controlling the wind base loads and structural responses of wooden pagodas and preserving architectural heritage via FEA.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.3 no.1
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• pp.47-53
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• 2022

The escape behavior of prey fish to predator attack is directly linked to the survival of the fish. In this study, I explored the escape behavior of Medaka fish to bird attacks. To simulate the attack, I designed a model triangular-shaped bird to slide along a fishing line connected between rods at both ends of the tank. The triangular shape was set to 10×15 (S=1), 15×20 (S=2), and 20×25 cm (S=3) with base×height. The slope (θ) of the fishing line, which determines the attack speed of the model bird, was set to values of 15° (θ=1), 30° (θ=2), and 45° (θ=3). The escape behavior was characterized using five variables: escape speed (ν), escape acceleration (α), responsiveness (γ), branch length similarity entropy (ε), and alignment (ϕ). The experimental results showed when (S, θ)=(fixed, varied), the change in values of the five variables were not significant. Thus, the fish respond more sensitively to S than to θ In contrast, when (S, θ)=(varied, fixed), ν, α, and γ showed increasing trends but ε and ϕ did not change much. This indicates the nature of fish escape behavior irrespective of the threat is inherent in ε and ϕ. I found that fish escape behavior can be divided into two types for the five physical quantities. In particular, the analysis showed that the type was mainly determined by the size of the model bird.

• Earthquakes and Structures
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• v.23 no.6
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• pp.517-526
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• 2022

Previous studies have shown that pile-soil interactions have significant influences on the isolation efficiency of an isolated structure. However, most of the existing tests were carried out using a 1-g shaking table, which cannot reproduce the soil stresses resulting in distortion of the simulated pile-soil interactions. In this study, a centrifuge shaking table modelling of the seismic responses of a friction pendulum bearing isolated structure with a pile foundation under earthquakes were conducted. The pile foundation structure was designed and constructed with a scale factor of 1:100. Two layers of the foundation soil, i.e., the bottom layer was made of plaster and the upper layer was normal soil, were carefully prepared to meet the similitude requirement. Seismic responses, including strains, displacement, acceleration, and soil pressure were collected. The settlement of the soil, sliding of the isolator, dynamic amplification factor and bending moment of the piles were analysed to reveal the influence of the soil structure interaction on the seismic performance of the structure. It is found that the soil rotates significantly under earthquake motions and the peak rotation is about 0.021 degree under 24.0 g motions. The isolator cannot return to the initial position after the tests because of the unrecoverable deformation of the soil and the friction between the curved surface of the slider and the concave plate.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.503-518
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• 2023

In tall constructions, the outriggers are regarded as a structural part capable of effectively resisting lateral loads. This study analyses the efficacy of hybrid outrigger system in high rise RCC building for various structural parameters identified. For variations in α, which is defined as the ratio of the relative flexural stiffness of the core to the axial rigidity of the column, static and dynamic analyses of hybrid outrigger system having a virtual and a conventional outrigger at two distinct levels were conducted in the present study. An investigation on the optimal outrigger position was performed by taking the results from absolute maximum inter storey drift ratio (ISD_max), roof acceleration (acc_roof), roof displacement (disp_roof), and base bending moment under both wind and seismic loads on analytical models having 40, 60 and 80 storeys. An ideal performance index parameter was introduced and was utilized to obtain the optimal position of the hybrid outrigger system considering the combined response of ISD_max, acc_roof, disp_roof and, criteria required for the structure under wind and seismic loads. According to the behavioural study, increasing the column area and outrigger arm length will maximise the performance of the hybrid outrigger system. The analysis results are summarized in a flowchart which provides the optimal positions obtained for each dependent parameter and based on ideal performance index which can be used to make initial suggestions for installing a hybrid outrigger system.

• International Journal of High-Rise Buildings
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• v.12 no.3
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• pp.251-262
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• 2023

In response to China's "Regulations on the Management of Earthquake Resistance of Building Constructions" on the provision of eight types of important buildings to maintain functional after fortified earthquakes occur, "Guidelines for Seismic Design of post-quake functional buildings (Draft for Review)" distinguishes Class I and Class II buildings, and gives the performance objectives and seismic verification requirements for design earthquakes and severe earthquakes respectively. In this paper, a hospital and a school building are selected as examples to design according to the requirements of fortification of Intensity 8 and 7 respectively. Two design strategies, the seismic isolation scheme and energy dissipation scheme, are considered which are evaluated through elastic-plastic dynamic time-history analysis to meet the requirement of post-quake functional buildings. The results show that the seismic isolation design can meet the requirements in the above cases, and the energy dissipation scheme is difficult to meet the requirements of the "Guidelines" on floor acceleration in some cases, for which the scheme shall be made valid through the seismic resilience assessment. The research in this paper can provide a reference for designers to choose schemes for post-quake functional buildings.

• Geomechanics and Engineering
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• v.36 no.3
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• pp.277-293
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• 2024

Shored Mechanically Stabilized Earth (SMSE) walls are types of soil retaining structures that increase soil stability under static and dynamic loads. The damage caused by an earthquake can be determined by evaluating the probabilistic seismic response of SMSE walls. This study aimed to assess the seismic performance of SMSE walls and provide fragility curves for evaluating failure levels. The generated fragility curves can help to improve the seismic performance of these walls through assessing and controlling variables like backfill surface settlement, lateral deformation of facing, and permanent relocation of the wall. A parametric study was performed based on a non-linear elastoplastic constitutive model known as the hardening soil model with small-strain stiffness, HSsmall. The analyses were conducted using PLAXIS 2D, a Finite Element Method (FEM) program, under plane-strain conditions to study the effect of the number of geogrid layers and the axial stiffness of geogrids on the performance of SMSE walls. In this study, three areas of damage (minor, moderate, and severe) were observed and, in all cases, the wall has not completely entered the stage of destruction. For the base model (Model A), at the highest ground acceleration coefficient (1 g), in the moderate damage state, the fragility probability was 76%. These values were 62%, and 54%, respectively, by increasing the number of geogrids (Model B) and increasing the geogrid stiffness (Model C). Meanwhile, the fragility values were 99%, 98%, and 97%, respectively in the case of minor damage. Notably, the probability of complete destruction was zero percent in all models.