• Geomechanics and Engineering
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• 제5권2호
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• pp.143-164
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• 2013

Calculation of seismic displacements in reinforced slopes plays a crucial role in appropriate design of these structures however current analytical methods result indifferent values for permanent displacements of the slope. In this paper, based on limit equilibrium and using the horizontal slices method, a new formulation has been proposed for estimating the seismic displacements of a reinforced slope under earthquake records. In this method, failure wedge is divided into a number of horizontal slices. Assuming linear variations for tensile forces of reinforcements along the height of the slope, the coefficient of yield acceleration has been estimated. The simplicity of calculations and taking into account the frequency content of input triggers are among the advantages of the present formulation. Comparison of the results shows that the yield acceleration calculated by the suggested method is very close to the values resulted from other techniques. On the other hand, while there is a significant difference between permanent displacements, the values obtained from the suggested method place somehow between those calculated by the other techniques.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1225-1256
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• 2014

Calculating the seismic displacement of retaining walls has an important role in the optimum design of these structures. Also, studying the effect of surcharge is important for the calculation of active pressure as well as permanent displacements of the wall. In this regard, some researchers have investigated active pressure; but, unfortunately, there are few investigations on the seismic displacement of retaining walls with surcharge. In this research, using limit analysis and upper bound theorem, permanent seismic displacement of retaining walls with surcharge was analyzed for sliding and overturning failure mechanisms. Thus, a new formulation was presented for calculating yield acceleration, critical angle of failure wedge, and permanent displacement of retaining walls with surcharge. Also, effects of surcharge, its location and other factors such as height of the wall and internal friction angle of soil on the amount of seismic displacements were investigated. Finally, designing charts were presented for calculating yield acceleration coefficient and angle of failure wedge.

• Structural Engineering and Mechanics
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• 제42권2호
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• pp.247-267
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• 2012

Calculating the displacements of retaining walls under seismic loads is a crucial part in optimum design of these structures and unfortunately the techniques based on active seismic pressure are not sufficient alone for an appropriate design of the wall. Using limit analysis concepts, the seismic displacements of retaining walls are studied in present research. In this regard, applying limit analysis method and upper bound theorem, a new procedure is proposed for calculating the yield acceleration, critical angle of failure wedge, and permanent displacements of retaining walls in seismic conditions for two failure mechanisms, namely sliding and sliding-rotational modes. Also, the effect of internal friction angle of soil, the friction angle between wall and soil, maximum acceleration of the earthquake and height of the wall all in the magnitude of seismic displacements has been investigated by the suggested method. Two sets of ground acceleration records related to near-field and far-field domains are employed in analyses and eventually the results obtained from the suggested method are compared with those from other techniques.

• 한국지리정보학회지
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• 제14권4호
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• pp.137-149
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• 2011

284개의 IGS GPS 관측소와 한반도 및 인근 섬들에 위치한 22개 GPS 관측소의 관측 데이터를 이용하여 2011년 3월 11일에 발생한 진도 9.0Mw의 Tohoku-Oki 지진이 아시아 및 한국의 GPS 상시관측소에 미친 위치변동량을 분석하였다. GPS 관측데이터는 지진발생일을 기준으로 전후 7일씩 총 15일간 수신자료를 이용하였으며, GAMIT/GLOBK 소프트웨어를 이용하여 등진역 변위와 지진 후 변위를 해석하였다. 연구 결과, Tohoku-Oki 지진의 영향이 광범위 하여 진앙 중심으로부터 2,702km 떨어진 GPS 상시관측소에서도 등진역 변위가 발생한 것으로 나타났으며, 일본과 가까운 한국, 중국, 대만, 러시아 등 여러 국가에서도 지진의 영향이 확인되었다. 또한, Tohoku-Oki 지진은 한국의 GPS 상시관측소에 최소 14.9mm에서 최대 58.3mm에 이르는 위치변동량을 발생시켜 측지기준망의 성과를 새롭게 정비하지 않고 GPS 측량을 수행하는 경우 최대 20mm에 이르는 위치오차가 발생할 수 있을 것으로 판단되었다.

• Computers and Concrete
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• 제5권4호
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• pp.359-373
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• 2008

The present parametric study deals with the meso-scale modelling of concrete subjected to cyclic compression, which exhibits hysteresis loops during unloading and reloading. Concrete is idealised as a two-dimensional three-phase composite made of aggregates, mortar and interfacial transition zones (ITZs). The meso-scale modelling approach relies on the hypothesis that the hysteresis loops are caused by localised permanent displacements, which result in nonlinear fracture processes during unloading and reloading. A parametric study is carried out to investigate how aggregate density and size, amount of permanent displacements in the ITZ and the mortar, and the ITZ strength influence the hysteresis loops obtained with the meso-scale modelling approach.

• Geomechanics and Engineering
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• 제13권4호
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• pp.653-669
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• 2017

By increase in the population and consequently constructions, new structures may be built in vicinity of the soil slopes. Such structures can be regarded as an extra surcharge on the slopes. The intensity and location of the surcharge affects the displacements of the slopes. Few researchers have studied the effect of surcharge on displacements of soil slopes. In this research, using limit analysis method and upper bound theory with non-associated flow rule, displacements of soil slopes in vicinity of a surcharge has been estimated. The authors have improved the technique previously proposed by them and a new formulation is suggested for calculating the permanent displacements of the soil slope in presence of a surcharge for two failure modes, rotational and transitional. A comparison has also been made between the two mentioned modes for various conditions of surcharge and slope. The conditions resulting in the rotational mode to be more critical than the transitional mode have been investigated. Also, the effects of surcharge's intensity, location of surcharge as well as the soil properties have been investigated.

• 한국산업융합학회 논문집
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• 제26권2_1호
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• pp.231-238
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• 2023

This paper develops the theory for a novel fault-tolerant, permanent magnet biased, 6-active-pole, homopolar magnetic bearing. The Lagrange Multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrices for the failed bearing. some numerical examples of distribution matrices are provided to illustrate the new theory. Simulations show that very much the same dynamic responses (orbits or displacements) are maintained throughout failure events (up to any combination of 3 coils failed for the 6 pole magnetic bearing) while currents and fluxes change significantly. The overall load capacity of the bearing actuator is reduced as coils fail. The same magnetic forces are then preserved up to the load capacity of the failed bearing.

• Structural Engineering and Mechanics
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• 제69권3호
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• pp.243-255
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• 2019

Utilization of fiber beam-column element has gained considerable attention in recent years due mainly to its ability to model distributed plasticity over the length of the element through a number of integration points. However, the relatively high sensitivity of the method to modeling parameters as well as material behavior models can pose a significant challenge. Residual drift is one of the seismic demands which is highly sensitive to modeling parameters and material behavior models. Permanent deformations play a prominent role in the post-earthquake evaluation of serviceability of bridges affected by a near-fault ground shaking. In this research, the influence of distributed plasticity modeling parameters using both force-based and displacement-based fiber elements in the prediction of internal forces obtained from the nonlinear static analysis is studied. Having chosen suitable type and size of elements and number of integration points, the authors take the next step by investigating the influence of material behavioral model employed for the prediction of permanent deformations in the nonlinear dynamic analysis. The result shows that the choice of element type and size, number of integration points, modification of cyclic concrete behavior model and reloading strain of concrete significantly influence the fidelity of fiber element method for the prediction of permanent deformations.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.471-475
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• 2002

To detect ground subsidence, the permanent scatterer SAR interferometry is applied to the Shinho industrial complex. Eleven JERS-1 images were acquired in the study area between October 1996 and September 1998. All SAR data were co-registered to one master scene (January 8, 1998) and thus 10 interferograms were obtained in a time series. In order to determine permanent scatterers, coherence maps as well as the interferograms were generated and exploited. The coherence at the selected PSs was larger than 0.4 in a 515 sub-window and 0.5 in a 39 sub-window. Twenty-nine PSs within the reclaimed land and 8 PSs (as reference phase) outside the plant were selected for the analysis. The 29 PSs were grouped into 5 sub-groups. We removed the reference phase, which was estimated from 8 outside PSs that were considered as phases free of displacement, from the phases at PSs inside the plant. Residual phases could be interpreted as surface displacement and DEM error. The subsidence of about 40 cm was detected at group 4, while surface displacements were negligible in the rest groups.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1375-1381
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• 2007

In this paper, we propose a linear modeling and identical PD controller design scheme for the three-pole hybrid-type AMB recently developed in the laboratory, which consists of three permanent magnets, providing bias flux, three Hall diodes, measuring rotor displacements, and ring type permanent magnet bearing, stabilizing in axial and tilting directions. Along the three physical coordinates formed by three poles, we introduce the redundant coordinate system and three identical decoupled controllers to construct linear model. The experiments are also carried out in order to verify the effectiveness of proposed controller in stabilizing the transient and steady state response of rotor.