• Structural Engineering and Mechanics
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• 제25권3호
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• pp.291-310
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• 2007

Current seismic design guidelines in Japan are diverse in the seismic ground strain estimates, because the concepts on a horizontally propagating wave model are not consistent in various seismic design guidelines including gas, water and other underground structures. The purpose of this study is (a) to derive the analytical methods to estimate the ground strains for incident seismic waves, (b) to develop a statistical estimation technique of the ground strains, and finally (c) to compare the theoretical estimation with the observed data which was measured at 441 sites in the 1999 Chi-Chi Earthquake in Taiwan.

• Geomechanics and Engineering
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• 제24권1호
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• pp.67-79
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• 2021

The influence of ground motions on the seismic response of utility tunnels was investigated. A series of small-scale shaking table model tests were carried out under uniform excitation in the transverse direction. Different peak accelerations of EL-Centro and Taft earthquake waves were applied. The acceleration responses, earth pressure, seismic strain, bending moment and structure deformations were measured and discussed. The results showed that the types of earthquake waves had significant influences on the soil-structure acceleration responses. However, the amplitude of the soil acceleration along the depth showed consistent variation regardless of the types of earthquake waves and tunnels. The horizontal soil pressure near the top and bottom slabs showed obviously larger values than those at other depths. In general, the strain response in the outer surface was more significant than that on the inner surface, and the peak strain in the end section of the model was larger than that in the middle section. Moreover, the bending moment at the corner points was much larger than that at middle point, and the bending moment was greatly affected by both input accelerations and seismic wave types. The opposite direction of shear deformation on the top and bottom slabs presented a rotation trend of the model structure.

• Steel and Composite Structures
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• 제38권1호
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• pp.79-86
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• 2021

Due to the complex geological conditions, a large number of high quality coal seams was buried in the western of China which cannot be mining in open-pit methods. The dynamic properties of that coal cannot be studied easily in real site for the complex working condition. The compound coal blocks made on the basis of the real situation were studied in the laboratory. The physical and mechanical properties of the compound coal blocks and the raw coal were contrasted by using the UCS tests. The results show that the compound coal blocks made by mixing coal powder, cement and water in proportion of 2.5:2:1 are the closest to that of standard raw coal. Then the propagation of strain waves and crushing effects on the coal were studied in the compound coal blocks by using the super dynamic strain test system and the numerical calculated method of ANSYS/LS-DYNA. The results show that the diameter of the crushing zone in the compound coal blocks was similar to that in the numerical results. The fractures distribution in laboratory tests also has a similar trend to the calculation results. The measured strain waves at the distance of 50 cm, 100 cm, and 150 cm from the center of the charge are mainly concerned at -1.0×104 με and have a similar trend as that in the numerical simulation.

• 대한조선학회논문집
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• 제59권5호
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• pp.296-305
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• 2022

In order to investigate maneuvering characteristics of KCS in waves, captive model test in regular waves was conducted. Purpose of the test is measuring maneuvering hull forces when ship is maneuvering in waves. Model test was carried out using CPMC (Computerized Planar Motion Carriage) of ocean engineering basin in KRISO (Korea Research Institute of Ships and Ocean engineering). Total 6 degrees-of-freedom motion were fixed by two points supporting captive model test device, which is specially designed for this test. This system estimates 6 degrees-of-freedom forces and moments through 12 strain gauge signals. Mapping matrix from strain gauge signals to 6 degrees-of-freedom forces and moments was derived by a well-organized calibration test. Static drift test was conducted in calm sea and in regular waves with various wave conditions. Hydrodynamic coefficients related to drift angle were extracted for each wave conditions, and the effect of waves on course stability was analyzed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.515-520
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• 2005

The behavior of jointed rock mass is much different from that of intact rock due to the presence of joints. Similarly, the characteristics of elastic wave propagation in jointed rock are considerably different from those of intact rock. The propagation of elastic waves in jointed rock is greatly dependent on the state of stress. The roughness, filling materials, and spacing of joints also affect wave propagation in jointed rock. If the wavelength of elastic waves is much larger than the spacing between joints, wave propagation in jointed rock mass can be considered as wave propagation in equivalent continuum. A rock resonant column testing apparatus is made to measure elastic waves propagating through jointed rock in the state of equivalent continuum. Three types of wave, i.e, torsional, longitudinal and flexural waves are monitored during rock resonant column tests. Various roughness and filling materials are applied to joints, and rock columns with various spacings are used to understand how these factors affect wave propagation under a small strain condition. The experimental results suggest that the characteristics of wave propagation in jointed rock mass are governed by the state of stress and influenced by roughness, filling materials and joint spacings.

• 한국직업건강간호학회지
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• 제29권1호
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• pp.88-96
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• 2020

Purpose: This study aimed to identify the mental fitness, perspective taking, attitude toward the elderly, and quantitative encephalogram among caregivers. Methods: In this mixed method research, 14 female caregivers at an elderly care facility in Y city were participated from December 1st to December 31st, 2019. Structured questionnaires were applied to measure general characteristics, mental fitness, perspective taking, and attitude toward the elderly. Brain waves were measured by quantitative encephalogram in the prefrontal lobe. High frequency and high level of care tasks were analyzed using content analysis. Results: According to analysis of brain waves, caregivers experienced high level of physical strain & stress and psychological distraction & stress. Mental fitness (p<.05) and perspective taking (p<.001) were associated with attitude toward the elderly. Moreover, physical strain & stress was associated with psychological distraction & stress (p<.05, p<.001). High frequency and high level tasks were excretion and position change & movement care related tasks, respectively. Conclusion: These findings should be consider as an evidence for supporting care tasks based on concrete and objective understanding of caregivers using self-reported index as well as neurophysiological indicators including brain waves.

• Geomechanics and Engineering
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• 제16권1호
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• pp.11-19
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• 2018

Propagation of the generalized Rayleigh waves in an elastic half-space covered by an elastic layer for different initial stress combinations and imperfect contact conditions is investigated. Three-dimensional linearized theory of elastic waves in initially stressed bodies in plane-strain state is employed, the corresponding dispersion equation is derived and an algorithm is developed for numerical solution to this equation. Numerical results on the influence of the initial stress patterns and on the influence of the contact conditions are presented and discussed. The case where the external forces are "follower forces" is considered as well. These investigations provide some theoretical foundations for the study of the near-surface waves propagating in layered mechanical systems and can be successfully used for estimation of the degree of the bonded defects between layers, fault characteristics and study of the behavior of seismic surface waves propagating under the bottom of the oceans.

• Smart Structures and Systems
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• 제1권2호
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• pp.217-233
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• 2005

Elastic and electromagnetic waves can be used to gather important information about particulate materials. To facilitate smart geophysical characterization of particulate materials, their fundamental properties are discussed and experimental procedures are presented for both elastic and electromagnetic waves. The first application is related to the characterization of particulate materials using shear waves, concentrating on changes in effective stress during consolidation, multi-phase phenomena with relation to capillarity, and microscale characteristics of particles. The second application involves electromagnetic waves, focusing on stratigraphy detection in layered soils, estimation of void ratio and its spatial distribution, and conduction in unsaturated soils. Experimental results suggest that shear waves allow studying particle contact phenomena and the evolution of interparticle forces, while electromagnetic waves give insight into the characteristics of the fluid phase and its spatial distribution.

• Journal of Theoretical and Applied Mechanics
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• 제2권1호
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• pp.1-14
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• 1996

In this paper, breaking waves are generated in a 2-D wave tank and simulated by using a higher-order boundary element method. A piston-type wavemaker is operated by signals composed of elementary waves. The phase of elementary waves is determined by the linear theory such that they are focused to a prescribed position. Calculated plunging waves coincide well with experiment. A steel box with different plate thicknesses is installed at a predetermined position in the tank. Measured impulsive pressures due to breaking waves are found to be 0.8-1.2$\rho$C2, where $\rho$ corresponds to water density and C to wave celerity. The transverse displacement of the plate is described in terms of modal eigenfunctions. The natural frequencies measured by impact tests in air for thin plate coincide with the computational and theoretical values. The radiationpotential due to plate vibration is derived and the radiation force is expressed in terms of hydroelastic added mass and damping forces. Comparison of natural frequencies of plate in water proves that hydroelastic added mass and damping are properly considered. The measured strain due to regular waves supports the calculated one, but there are apparent discrepancies between theory and experiment in the impulsive case.

• Structural Engineering and Mechanics
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• 제61권2호
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• pp.221-230
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• 2017

In this paper, we investigated the propagation of thermoelastic surface waves in fibre-reinforced anisotropic general viscoelastic media of higher order of nth order including time rate of strain under the influence of rotation. The general surface wave speed is derived to study the effectsof rotation andthermal onsurface waves. Particular cases for Stoneley, Love and Rayleighwaves are discussed.The results obtained in this investigation are more general in the sense that some earlier published results are obtained from our result as special cases. Our results for viscoelastic of order zero are well agreed to fibre-reinforced materials. Comparison was made with the results obtained in the presence and absence of rotation and parameters for fibre-reinforced of the material medium. It is also observed that, surface waves cannot propagate in a fast rotating medium.Numerical results for particular materials are given and illustrated graphically. The results indicate that the effect of rotation on fibre-reinforced anisotropic general viscoelastic media are very pronounced.