• Smart Structures and Systems
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• v.3 no.4
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• pp.423-437
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• 2007

The empirical mode decomposition (EMD) method is well-known for its ability to decompose a multi-component signal into a set of intrinsic mode functions (IMFs). The method uses a sifting process in which local extrema of a signal are identified and followed by a spline fitting approximation for decomposition. This method provides an effective and robust approach for decomposing nonlinear and non-stationary signals. On the other hand, the IMF components do not automatically guarantee a well-defined physical meaning hence it is necessary to validate the IMF components carefully prior to any further processing and interpretation. In this paper, an attempt to use the EMD method to identify properties of nonlinear elastic multi-degree-of-freedom structures is explored. It is first shown that the IMF components of the displacement and velocity responses of a nonlinear elastic structure are numerically close to the nonlinear normal mode (NNM) responses obtained from two-dimensional invariant manifolds. The IMF components can then be used in the context of the NNM method to estimate the properties of the nonlinear elastic structure. A two-degree-of-freedom shear-beam building model is used as an example to illustrate the proposed technique. Numerical results show that combining the EMD and the NNM method provides a possible means for obtaining nonlinear properties in a structure.

• Journal of Aerospace System Engineering
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• v.11 no.2
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• pp.16-22
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• 2017

This paper investigates fretting wear damage in aerospace, biomedical, and nuclear components. Experimental parameters are identified that affect fretting wear damage. The parameters observed in industries are directly compared. The magnitudes of frequency, relative displacement, and normal force are found to differ depending on the contacting components where fretting wear occurs. In addition, recent solutions to minimize fretting wear damage are reviewed. The solutions include depositing of a low-friction coating, surface treatment, selection of substrate material, and optimal design of contact geometries. This comparative study suggests useful methods and solutions for analyzing fretting wear damage and for designing tribo-components.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.3
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• pp.127-136
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• 2022

Recently, an unprecedented emerging infectious disease has rapidly spread, causing a global shortage of wards. Although various temporary beds have appeared, the supply of wards specializing in infectious diseases is required. Negative pressure isolation wards should maintain their function even after an earthquake. However, the current seismic design standards do not guarantee the negative pressure isolation wards' operational (OP) performance level. For this reason, some are not included in the design target even though they are non-structural elements that require seismic design. Also, the details of non-structural elements are usually determined during the construction phase. It is often necessary to complete the stability review and reinforcement design for non-structural elements within a short period. Against this background, enhanced performance objectives were set to guarantee the OP non-structural performance level, and a computerized tool was developed to quickly perform the seismic design of non-structural elements in the negative pressure isolation wards. This study created a spreadsheet-based computer tool that reflects the components, installation spacing, and design procedures of non-structural elements. Seismic performance review and design of the example non-structural elements were conducted using the computerized tool. The strength of some components was not sufficient, and it was reinforced. As a result, the time and effort required for strength evaluation, displacement evaluation, and reinforcement design were reduced through computerized tools.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.160-166
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• 2024

In recent years, as buildings have become taller and taller, the continued usability of elevators after earthquakes has become an important issue. Conventional seismic design of elevators has focused mainly on inertial forces caused by earthquakes, but the influence of the story drift angle of buildings on elevator behavior has been unclear. Therefore, the objective of this study was to clarify the influence of the story drift angle of a building caused by an earthquake on the behavior of elevators through an experiment. The experiment specimens were the counterweight, guide rails, and surrounding components selected from the actual elevator components and mounted on a one-story steel pin frame. A static experiment was conducted using a hydraulic jack to apply force to the specimen by imposing the story drift angle on the steel frame. During the experiment, the reaction force at the end of the jack was monitored, and the displacement and strain of the counterweight, guide rails, and surrounding components were measured. The results of the experiments in one direction showed that even when the elevator components were subjected to a larger story drift angle than assumed in the seismic design of the building, no damage occurred that could lead to fallout.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.4
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• pp.317-322
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• 2003

This paper have calculated a relative heights of an each station using the data which were observed by GPS permanent stations(Chejudo, Homigoj, Jumunjin, Marado, Palmido, Ulengdo, Youndo) established in Korea. We performed spectrum analysis with a calculated relative heights by CLEAN algorithm. Through these process, we estimated vertical displacement of earth surface by semi-dinural ocean tidal loading components, and compared them with the results which were calculated by improving ocean tide model(NA099jb) for adjacent seas around Japan and Korea. As the result of this study, we determined the ocean tidal loading components with loading effects of $M_2$ and $N_2$, and we noted that the amplitude and the phase lags of ocean tidal loading components from observed GPS data were almost equal to values calculated from ocean tide models. However, the loading components about semi-diurnal tide $S_2$, $K_2$ couldn't estimate because of periods. Also, the diurnal ocean tide loading components were not considered, because the noise level have increased during the diurnal frequency.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1569-1582
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• 2015

This study explores the lateral deflections of diagonal braces in concentrically-braced earthquake-resisting frames. The performance of this widely-used system is often compromised by the flexural buckling of slender braces in compression. In addition to reducing the compressive resistance, buckling may also cause these members to undergo sizeable lateral deflections which could damage surrounding structural components. Different approaches have been used in the past to predict the mid-length lateral deflections of cyclically loaded steel braces based on their theoretical deformed geometry or by using experimental data. Expressions have been proposed relating the mid-length lateral deflection to the axial displacement ductility of the member. Recent experiments were conducted on hollow and concrete-filled circular hollow section (CHS) braces of different lengths under cyclic loading. Very slender, concrete-filled tubular braces exhibited a highly ductile response, undergoing large axial displacements prior to failure. The presence of concrete infill did not influence the magnitude of lateral deflection in relation to the axial displacement, but did increase the number of cycles endured and the maximum axial displacement achieved. The corresponding lateral deflections exceeded the deflections observed in the majority of the previous experiments that were considered. Consequently, predictive expressions from previous research did not accurately predict the mid-height lateral deflections of these CHS members. Mid-length lateral deflections were found to be influenced by the member non-dimensional slenderness (${\bar{\lambda}}$) and hence a new expression was proposed for the lateral deflection in terms of member slenderness and axial displacement ductility.

• The Journal of Advanced Prosthodontics
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• v.10 no.2
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• pp.138-146
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• 2018

PURPOSE. The purpose of this study was to analyze the effects of the splinted implant prosthesis in a reconstructed mandible using three-dimensional finite element analysis. MATERIALS AND METHODS. Three-dimensional finite element models were generated from a patient's computed tomography data. The patient had undergone partial resection of the mandible that covered the area from the left canine to the right condyle. The mandible was reconstructed using a fibula bone graft and dental implants. The left mandibular premolars and molars remained intact. Three types of models were created. The implant-supported prosthesis was splinted and segmented into two or three pieces. Each of these models was further subcategorized into two situations to compare the stress distribution around normal teeth and implants. Oblique loading of 300 N was applied on both sides of the mandible unilaterally. The maximum von Mises stress and displacement of the models were analyzed. RESULTS. The stress distribution of the natural mandible was more uniform than that of the reconstructed fibula. When the loading was applied to the implant prosthesis of reconstructed fibula, stress was concentrated at the cortical bone around the neck of the implants. The three-piece prosthesis model showed less uniform stress distribution compared to the others. Displacement of the components was positively correlated with the distance from areas of muscle attachment. The three-piece prosthesis model showed the greatest displacement. CONCLUSION. The splinted implant prosthesis showed a more favorable stress distribution and less displacement than the separated models in the reconstructed mandible.

• Progress in Medical Physics
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• v.17 no.4
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• pp.207-211
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• 2006

The advent of kV cone-beam computed tomography (CBCT) integrated with a linear accelerator allows for more accurate Image-guided radiotherapy (IGRT). IGRT is the technique that corrects target displacement based on internal body information. To do this, the CBCT Image set is acquired just before the beam is delivered and registered with the simulation CT Image set. In this study, we compare the registration results according to the CBCT's reconstruction quality (either high or medium). A total of 56 CBCT projection data from 6 patients were analyzed. The translation vector differences were within 1 mm in all but 3 cases. For rotation displacement difference, components of all three axes were considered and 3 out of 168 ($56{\times}3$ axes) cases showed more than lo of rotation differences.

• Earthquakes and Structures
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• v.23 no.2
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• pp.169-181
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• 2022

To research the dynamic response of the high-rise structure under the rocking ground motion, which we believed that the effect cannot be ignored, especially accompanied by vertical ground motion. Theoretical analysis and shaking table seismic simulation tests were used to study the response of a high-rise structure to excitation of a H-V-R ground motion that included horizontal, vertical, and rocking components. The use of a wavelet analysis filtering technique to extract the rocking component from data for the primary horizontal component in the first part, based on the principle of horizontal pendulum seismogram and the use of a wavelet analysis filtering technique. The dynamic equation of motion for a high-rise structure under H-V-R ground motion was developed in the second part, with extra P-△ effect due to ground rocking displacement was included in the external load excitation terms of the equation of motion, and the influence of the vertical component on the high-rise structure P-△ effect was also included. Shaking table tests were performed for H-V-R ground motion using a scale model of a high-rise TV tower structure in the third part, while the results of the shaking table tests and theoretical calculation were compared in the last part, and the following conclusions were made. The results of the shaking table test were consistent with the theoretical calculation results, which verified the accuracy of the theoretical analysis. The rocking component of ground motion significantly increased the displacement of the structure and caused an asymmetric displacement of the structure. Thus, the seismic design of an engineering structure should consider the additional P-△ effect due to the rocking component. Moreover, introducing the vertical component caused the geometric stiffness of the structure to change with time, and the influence of the rocking component on the structure was amplified due to this effect.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.228-231
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• 1996

In this paper, we calculate the thrust force by the permeance method. we analyze the thrust force vs. displacement and harmonic components of static thrust characteristics of LPM. Microstep reference current for cancelation of the dominent harmonic component is obtained by the analytical method.