• Earthquakes and Structures
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• 제19권2호
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• pp.103-117
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• 2020

The effect of the foundation size on the efficiency of seismic base isolation using a layer of stone pebbles is experimentally investigated. Four scaled models of buildings with different stiffnesses (from very stiff to soft) were tested, each with the so-called small and large foundation, and exposed to four different accelerograms (different predominant periods and durations). Tests were conducted so that the strains in the model remained elastic and afterwards the models were tested until collapse. Each model was tested for the case of the foundation being supported on a rigid base and on an aseismic layer. Compared to the smaller foundation, the larger foundation results in a reduced rocking effect, higher earthquake forces and lower bearing capacity of the tested models, with respectable efficiency (reduced strain/stress, displacement and increase of the ultimate bearing capacity of the model) for the considered seismic base isolation compared to the foundation on a rigid base.

• 한국지반공학회논문집
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• 제28권7호
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• pp.67-75
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• 2012

교량기초의 지지층인 조밀한 화강풍화토 지반에서 얕은 기초의 침하에 대한 크기효과를 평가하고자 하였다. 이를 위해 지반조건이 유사한 2개 현장에서 재하판 크기를 다르게 하여 평판재하시험을 수행하였다. 시험결과 재하판 하부 및 주변 지반의 파괴는 관찰되지 않았으며 하중 증가에 따라 침하가 비례하여 증가하였다. 이러한 결과는 대상지반에 지지되는 기초의 안정성 또는 사용성은 침하가 지배하는 것을 의미한다. 침하에 대한 기초크기 효과는 압력-침하곡선의 기울기로 표현되는 지반반력계수와 기초폭의 관계로 표현하였다. 기존에 제안된 관계식과 비교해 볼 때 본 실험결과는 크기효과가 더 크게 나타나며, 이는 기존에 제안된 관계식은 조밀한 화강풍화토 지반에 지지된 기초의 침하를 과소평가할 수 있음을 나타낸다.

• Structural Engineering and Mechanics
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• 제73권2호
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• pp.191-207
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• 2020

This study aims at investigating the size-dependent free vibration of porous nanoplates when exposed to hygrothermal environment and rested on Kerr foundation. Based on the modified power-law model, material properties of porous functionally graded (FG) nanoplates are supposed to change continuously along the thickness direction. The generalized nonlocal strain gradient elasticity theory incorporating three scale factors (i.e. lower- and higher-order nonlocal parameters, strain gradient length scale parameter), is employed to expand the assumption of second shear deformation theory (SSDT) for considering the small size effect on plates. The governing equations are obtained based on Hamilton's principle and then the equations are solved using an analytical method. The elastic Kerr foundation, as a highly effected foundation type, is adopted to capture the foundation effects. Three different patterns of porosity (namely, even, uneven and logarithmic-uneven porosities) are also considered to fill some gaps of porosity impact. A comparative study is given by using various structural models to show the effect of material composition, porosity distribution, temperature and moisture differences, size dependency and elastic Kerr foundation on the size-dependent free vibration of porous nanoplates. Results show a significant change in higher-order frequencies due to small scale parameters, which could be due to the size effect mechanisms. Furthermore, Porosities inside of the material properties often present a stiffness softening effect on the vibration frequency of FG nanoplates.

• Advances in nano research
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• 제7권5호
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• pp.337-349
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• 2019

The size-dependent vibration analysis of a cross-/angle-ply laminated composite plate when embedded on the Pasternak elastic foundation and exposed to an in-plane magnetic field are investigated by adopting an analytical eigenvalue approach. The formulation, which is based on refined-hyperbolic-shear-deformation-plate theory in conjunction with the Eringen Nonlocal Differential Model (ENDM), is tested against considering problems for which numerical/analytical solutions available in the literature. The findings of this study demonstrated the role of magnetic field, size effect, elastic foundation coefficients, geometry, moduli ratio, lay-up numbers and fiber orientations on the nonlocal frequency of cross-/angle-ply laminated composite plates.

• Structural Engineering and Mechanics
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• 제71권1호
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• pp.37-43
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• 2019

This paper studies application of modified couple stress theory and first order shear deformation theory to magneto-electro-mechanical vibration analysis of three-layered size-dependent curved beam. The curved beam is resting on Pasternak's foundation and is subjected to mechanical, magnetic and electrical loads. Size dependency is accounted by employing a small scale parameter based on modified couple stress theory. The magneto-electro-mechanical preloads are accounted in governing equations to obtain natural frequencies in terms of initial magneto-electro-mechanical loads. The analytical approach is applied to investigate the effect of some important parameters such as opening angle, initial electric and magnetic potentials, small scale parameter, and some geometric dimensionless parameters and direct and shear parameters of elastic foundation on the magneto-electro-elastic vibration responses.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.300-307
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• 2002

Bridge foundation failure considering the effect of local scour around pier foundations under hi-directional seismic excitations is examined in probabilistic perspectives. The seismic responses of bridges with deep foundations are evaluated with a simplified mechanical model, which can consider the local scour effect around the deep foundation in addition to many other components. The probabilistic characteristics of local scour depths are estimated by using the Monte Carlo simulation. The probabilistic characteristics of basic random variables used in the Monte Carlo simulation are determined from the actual hydraulic data collected in middle size streams in Korea. The failure condition of deep foundation is assumed as bearing capacity failure of the ground below the foundation base. The probability of foundation failure of a simply supported bridge with various scour conditions and hi-directional seismic excitations are examined. It is found that the local scour and the recovery duration are critical factors in evaluating the probability of foundation failure. Moreover, the probability of foundation failure under hi-directional seismic excitations is much higher than under uni-directional seismic excitations. Therefore, it is reasonable to consider hi-directional seismic excitations in evaluating the seismic safety of bridge systems scoured by a flood.

• 한국지진공학회논문집
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• 제3권1호
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• pp.113-122
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• 1999

일본 고베지진후 구조물 수직방향 내진거동의 중요성은 잘 인식되었으나 대부분의 내진설계규준에서는 지반조건을 규정하지 않아 수직방향 구조물 내진해석시 대개 토질과 기초조건을 무시하고 수행하였다 이 논문에서는 연약지반이 Taft 지진과 El Centro 지진의 수직방향 지진하중을 받는 구조물의 수직방향 반응에 미치는 영향을 알아보기 위해 기초크기, 기초 및 지반깊이 , 기초근입깊이 및 말뚝기초가 수직방향 내진반응스펙트럼에 미치는 영향에 대해 연구하였는데 지반은 UBC-97에서 분류한 Sa. Sc. SE를 기초크기는 중 대형 기초를. 기초 및 지반깊이는 30m 와 60m를 기초근입깊이를 0m와 15m를 고려하였으며 연약지반에 설치한 말뚝은 기성제 콘크리트 선단지지말뚝을 고려하였다 연구결과에 의하면 기초크기는 구조물의 수직방향 내진반응에 별 영향이 없지만 지반깊이는 수평방향 내진해석에서처럼 기초 및 60m까지 고려해야 하며 연약지반위에 설치된 묻힌기초와 얕은 말뚝기초는 구조물의 수직방향 내진거동을 크기 증폭시켰다.

• The Journal of Korean Physical Therapy
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• 제32권5호
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• pp.277-282
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• 2020

Purpose: The main purposes of this study are to identify the degree of effect size and variables related to it, on the effect of physical therapy on shoulder adhesive capsulitis. Methods: This study were collected 8 studies published between 2010.01.01. and 2020.08.01. The Analysis result confirmed 16 effect size data, the random effect model was chosen because of the heterogeneity of the data. Results: First, full case showed the largest mean effect size 3.28 (p<0.001). Second, Size of the effect according to hands on+off intervention the 5.17 (p>0.344). Third, Number of participants showed 15 or more effect size 4.19 (p<0.002). intervention period showed 8 weeks effect size 5.12 (p>0.425). Number of intervention showed 14 or less effect size 3.99 (p>0.061). Publication type showed thesis effect size 4.34 (p<0.003). Finally, 'Trim and Fill' result confirmed that the calibration effect size is 1.71 (p<0.001). Conclusion: We were able to confirm that physical therapy had great effect on shoulders adhesive capsulitis, and that the effect differed according to the methods of intervention, the methods of evaluation.

• The Journal of Korean Physical Therapy
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• 제32권4호
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• pp.222-227
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• 2020

Purpose: The primary purposes of this study were to identify the degree of the effect size and the variables related to it on the effects of physical therapy on myofascial pain syndrome. Methods: This study collected 15 studies published between 2008.01.01 and 2019.12.31. The Analysis results confirmed 57 effect size data. The random-effect model was chosen because of the heterogeneity of the data. Results: First, the full case showed the largest mean effect size of 2.03 (p<0.001). Second, the size of the effect, according to the handson intervention, was 2.74 (p<0.003). Third, the VAS showed an effect size of 2.30 (p<0.001). Fourth, the intervention period showed a 1- to 15-day effect size of 2.94 (p<0.001). The number of interventions showed a 6 to 10 effect size of 2.84 (p<0.006). The number of participants showed a 10 or less effect size of 2.66 (p<0.001). Finally, the 'Trim and Fill' result confirmed that the calibration effect size was 0.93 (p<0.001). Conclusion: Physical therapy had a great effect on myofascial pain syndrome in the neck and shoulders, and that the effect differed according to the methods of the intervention and the methods of evaluation.

• 대한물리의학회지
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• 제15권4호
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• pp.21-28
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• 2020

PURPOSE: The main purpose of this meta-analysis study was to identify the degree-of-effect size and the variables for the effects of manual physical therapy on myofascial pain syndrome. METHODS: This study collected six studies published between 2015.01.01 and 2019.12.31. The analysis result verified nine effect size data. The random-effect model was chosen because of the heterogeneity of the data. RESULTS: First, the full case showed the largest mean effect size of 2.297 (p < .001). Second, the size of the effect based on the fascial distortion model (FDM) intervention showed an effect size of 4.654 (p < .001). Third, the number of participants showed a 15 or less effect size of 2.612 (p > .058). The number of treatments showed a 10 less effect size of 2.844 (p > .129). The publication type showed a thesis effect size of 3.095 (p < .002). CONCLUSION: Manual physical therapy has a great effect on myofascial pain syndrome in the neck and shoulders, and that the effects differ according to the methods of intervention.