• 한국산업융합학회 논문집
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• 제5권1호
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• pp.65-74
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• 2002

This paper intends to investigate such effects through experiments. The contents of the investigation are effects of position of repeated loading and unloading, passing frequency. For the purpose of the investigation an experimental load-deflection system is developed and the system is possible to measure deflection of the wall and earth pressure due to different size of strip loading and cyclic loading. The findings from the experiments are as follows: 1. As repeated loading approaches to the wall, the measured horizontal residual earth pressure agrees well with Rowe's empirical formula, while as the loading is far from the wall the earth pressure consists with Boussinesq's and Spangler's formulas. Also it is found that below 0.6m depth from ground surface the effects of repeated loading can be nearly neglected. 2. From comparison analyses of earth pressure theories and experimental results, a reagression equation is suggested herein, and earth pressure at any depth and maximum earth pressure due to cyclic loading can be estimated from the equation.

• Geomechanics and Engineering
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• 제16권5호
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• pp.463-469
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• 2018

In offshore engineering, lateral cyclic loading may induce excessive lateral movement and bending strain in pile foundations. Previous studies mainly focused on deformation mechanisms of single piles due to lateral cyclic loading. In this paper, centrifuge model tests were conducted to investigate the response of a $2{\times}2$ pile group due to lateral cyclic loading in clay. After applying each loading-unloading cycle, the pile group cannot move back to its original location. It implies that residual movement and bending strain are induced in the pile group. This is because cyclic loading induces plastic deformation in the soil surrounding the piles. As the cyclic load increases from 62.5 to 375 kN, the ratio of the residual to the maximum pile head movements varies from 0.30 to 0.84. Moreover, the ratio of the residual to the maximum bending strains induced in the piles is in a range of 0.23 to 0.82. The bending strain induced in the front pile is up to 3.2 times as large as that in the rear pile. Thus, much more protection measures should be applied to the front piles to ensure the serviceability and safety of pile foundations.

• 한국지반공학회지:지반
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• 제6권4호
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• pp.53-64
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• 1990

말뚝의 지지력을 예측키 위한 수많은 방안들이 제안되어 왔으나,말뚝 재하시험에 의하는 방법 외에는 신뢰도가 낮은 실정이다. 그럼에도 불구하고 말뚝 재하시험 수행에는 많은 비용과 시간이 소요되어 극히 제한된 경우에만 적용되고 있다. 본 연구에서는 새로운 말뚝재하시험, "간편한 말뚝 재하시험 (SPLT)방법"을 소개한다. SPLT에서는 분리할 수 있는 선단부와 축소된 선단부가 시험말 뚝에 설계되어, 주면마찰력이 말뚝 선단부의 침하를 야기시키는 반력으로 작용하게 된다. 이에 따라 하중재하장치 또는 하중의 제작,설치 및 제거 과정이 생략될 수 있다. 생략될 수 있다.

• 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.

• 대한기계학회논문집A
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• 제25권7호
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• pp.1097-1106
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• 2001

A telescopic handless is a kind of construction machinery for loading, carrying and unloading various cargos. A residual vibration of the boom, however, is often caused in carrying cargos to high workplace, especially in small motion and unloading operations, even when an expert of this machine handless the boom. To solve this vibrational problem, we applied TDC and newly proposed Commandless IST to the telescopic handler, and confirmed their effectiveness through experiments. These promising results show that the proposed control schemes can improve productivity, safety and ride comfort of the telescopic handler.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.246-248
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• 2005

The power plants have a loading dock and unloading device for the diverse kinds of fuel such as the bituminous coal and natural gas imported by the sea from all over the world. To unload the coal in the ship not only in the environment-friendly manner but also in the cost-effective way, the new type of heavy equipment loaded with additional features as well as excavator and the remote controller to maneuver this equipment are developed. This heavy equipment, which can be used to unload the coal in the ship in conjunction with CSU (Continuous Ship Unloader), and the remote controller are endorsed by the related code and laws. With the remote controller, the field workers can operate the unloading equipment at the remote place far from the equipment as well as in the cabin for themselves without tile remote controller.

• Geomechanics and Engineering
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• 제18권5호
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• pp.481-492
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• 2019

Due to the underground openings, the tangentially concentrated stress of the tunnel remains larger at excavation boundary and decreases toward the interior of the surrounding rock with a certain gradient. In order to study the effect of different gradient stress on rockburst, the true-triaxial gradient and hydraulic-pneumatic combined test apparatus were carried out to simulate the rockburst processes. Under the different gradient stress conditions, the rock-like specimen (gypsum) was tested independently through three principal stress directions loading--fast unloading of single surface--top gradient and hydraulic-pneumatic combined loading, which systematically analyzed the macro-mesoscopic damage phenomena, force characteristics and acoustic emission (AE) signals of the specimen during rockburst. The experimental results indicated that the rockburst test under the gradient and hydraulic-pneumatic combined loading conditions could perfectly reflect the rockburst processes and their stress characteristics; Relatively high stress loading could cause specimen failure, but could not determine its mode. The rockburst under the action of gradient stress suggested that the failure mode of specimen mainly depended on the stress gradient. When the stress gradient was lower, progressive and static spalling failure occured and the rockburst grades were relatively slight. On the other hand, shear fractures occurred in rockbursts accounted for increasingly large proportion as the stress gradient increased and the rockburst occurred more intensely and suddenly, the progressive failure process became unconspicuous, and the rockburst grades were moderate or even stronger.

• Geomechanics and Engineering
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• 제28권2호
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• pp.171-180
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• 2022

Time-dependent stress-strain behaviour significantly influences the compressibility characteristics of the clayey soil. In this paper, a series of oedometer tests were conducted in two loading patterns and investigated the time-dependent compressibility characteristics of Indian Montmorillonite Clay, also known as black cotton soil (BC) soil, during loading-unloading stages. The experimental data are analyzed using a new non-linear function of the Elasto-Visco-Plastic Model considering Swelling behaviour (EVPS model). From the experimental result, it is found that BC soil exhibits significant time-dependent behaviour during creep compared to the swelling stage. Pore water entrance restriction due to consolidated overburden pressure and decrease in cation hydrations are responsible factors. Apart from it, particle sliding is also evident during creep. The time-dependent parameters like strain limit, creep coefficient and C_αe/C_c are observed to be significant during the loading stage than the swelling stage. The relationship between creep coefficients and applied stresses is found to be nonlinear. The creep coefficient increases significantly up to 630 kPa-760 kPa (during reloading), and beyond it, the creep coefficient decreases continuously. Several parameters like loading duration, the magnitude of applied stress, loading history, and loading path have also influenced secondary compressibility characteristics. The time-dependent compressibility characteristics of BC soil are presented and discussed in detail.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1757-1760
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• 2005

This paper is concerned with spring back after sheet forming of bulk amorphous alloys in the super cooled liquid state. The temperature-dependence and strain-rate dependence of Newtonian/non-Newtonian viscosities as well as the stress overshoot/undershoot behavior of amorphous alloys are reflected in the thermo-mechanical Finite Element simulations. Hemispherical deep drawing operations are simulated for various forming conditions such as punch velocity, die corner radius, friction, blank holder force, clearance and initial forming temperature. Here, spring back by an instantaneous elastic unloading was followed by thermal deformation during cooling and two modes of spring backs are examined in detail. It could be concluded that the superior sheet formability of an amorphous alloy can be obtained by taking the proper forming conditions for loading/unloading.

• 소성∙가공
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• 제14권9호통권81호
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• pp.751-755
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• 2005

This paper is concerned with spring back after sheet forming of bulk amorphous alloys in the super cooled liquid state. The temperature-dependence and strain-rate dependence of Newtonian/non-Newtonian viscosities as well as the stress overshoot/undershoot behavior of amorphous alloys are reflected in the thermo-mechanical Finite Element simulations. Hemispherical deep drawing operations are simulated for various forming conditions such as punch velocity, die comer radius, friction, blank holder force, clearance and initial funning temperature. Here, spring back by an instantaneous elastic unloading was followed by thermal deformation during cooling, and two modes of spring back are examined in detail. It could be concluded that the superior sheet formability of an amorphous alloy can be obtained by taking the proper forming conditions for loading/unloading.