• Geomechanics and Engineering
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• v.23 no.2
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• pp.127-137
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• 2020

To study the reverse fault formation process and the stress evolution feature, a simulation test system of reverse fault formation is developed based on the analysis of reverse fault formation mechanism. The system mainly consists of simulation laboratory module, operation console and horizontal loading control system, and data monitoring system. It can represent the fault formation process, induce fault crack initiation and simulate faults of different throws. Simulation tests on reverse fault formation process are conducted by using the simulation test system: horizontal loading is added to one side of the model. the bottom rock layer cracks under the effect of the induction device. The crack dip angle is about 29°. A reverse fault is formed with the expansion of the crack dip angle towards the upper right along the fracture surface and the slippage of the hanging wall over the foot wall. Its formation process unfolds five stages: compressive deformation of rock, local crack initiation, reverse fault penetration, slippage of the hanging wall over the foot wall and compaction of fault plane. There is residual structural stress inside rock after fault formation. The study methods and results have guiding and referential significance for further study on reverse fault formation mechanism and rock stress evolution.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.17-27
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• 2017

The treatment of rotor wake has been a critical issue in the field of the rotor aerodynamics. This paper presents a new free wake model for the unsteady analysis for a wind turbine. A blade-wake-tower interaction is major source of unsteady aerodynamic loading and noise on the wind turbine. However, this interaction can not be considered in conventional free wake model. Thus, the free wake model named Finite Vortex Element (FVE hereafter) was devised in order to consider the interaction effects. In this new free wake model, the wake-tower interaction was described by dividing one vortex filament into two vortex filaments, when the vortex filament collided with a tower. Each divided vortex filaments were remodeled to make vortex ring and horseshoe vortex to satisfy Kelvin's circulation theorem and Helmholtz's vortex theorem. This model was then used to predict aerodynamic load and wake geometry for the horizontal axis wind turbine. The results of the FVE model were compared with those of the conventional free wake model and the experimental results of SNU wind tunnel test and NREL wind tunnel test under various inflow velocity and yaw condition. The result of the FVE model showed better correlation with experimental data. It was certain that the tower interaction has a strong effect on the unsteady aerodynamic load of blades. Thus, the tower interaction needs to be taken into account for the unsteady load prediction. As a result, this research shows a potential of the FVE for an efficient and versatile numerical tool for unsteady loading analysis of a wind turbine.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.537-551
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• 1998

The intention of this paper is to provide realistic values of design thermal loads applicable to composite box girder bridges on the basis of the statistical analysis of long-term measured temperature data. For this purpose, temperatures were recorded at a newly constructed composite box girder bridge during about 20 months. Before analyzing the extreme values, major thermal loading parameters that characterize the temperature profile are defined, and a seasonal behavior of those is examined in detail. The limit distributions of the thermal loading parameters are then determined by the tail-equivalence method, and the thermal loading parameters corresponding to selected return period are calculated. Finally, the results are compared to the specifications suggested in a current design code for thermal loads, and it is concluded that the current design code is unsuitable for representing the self-equilibrated thermal stresses in composite bridges, and the horizontal temperature difference which is not suggested in current design code should be taken Into account in particular cases.

• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.103-116
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• 2014

This paper presents the results of a numerical investigation on the load carrying capacity and consolidation behavior of suction piles. Three dimensional numerical models which reflect realistic ground conditions and installation procedures including the ground-suction pile interface were adopted to conduct a parametric study on variables such as the length-diameter ratio and the loading configurations, i.e, vertical, horizontal, and combined loads. The results indicated that the load carrying capacity of a suction pile can only be realistically obtained when the interface behavior between the suction pile and the ground is correctly modeled. Also carried out was the stress-pore pressure coupled analysis to investigate the consolidation behavior of the suction pile after the application of a vertical loading. Based on the results, failure envelops and associated equations were developed, which can be used to estimate load carrying capacity of suction piles installed in similar conditions considered in this study. The results of consolidation analysis based on the stress-pore pressure coupled analysis indicate that no significant excess pore pressure and associated consolidation settlement occur for the loading configuration considered in part due to the load transfer mechanism of the suction pile.

• Steel and Composite Structures
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• v.33 no.6
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• pp.793-803
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• 2019

Concrete-filled steel tubular (CFST) beam-columns are widely used owing to their good performance. They have high strength, ductility, large energy absorption capacity and low costs. Externally stiffened CFST beam-columns are not used widely due to insufficient design equations that consider all parameters affecting their behavior. Therefore, effect of various parameters (global, local slenderness ratio and adding hoop stiffeners) on the behavior of CFST columns is studied. An experimental study that includes twenty seven specimens is conducted to determine the effect of those parameters. Load capacities, vertical deflections, vertical strains and horizontal strains are all recorded for every specimen. Ratio between outer diameter (D) of pipes and thickness (t) is chosen to avoid local buckling according to different limits set by codes for the maximum D/t ratio. The study includes two loading methods on composite sections: steel only and steel with concrete. The case of loading on steel only, occurs in the connection zone, while the other load case occurs in steel beam connecting externally with the steel column wall. Two failure mechanisms of CFST columns are observed: yielding and global buckling. At early loading stages, steel wall in composite specimens dilated more than concrete so no full bond was achieved which weakened strength and stiffness of specimens. Adding stiffeners to the specimens increases the ultimate load by up to 25% due to redistribution of stresses between stiffener and steel column wall. Finally, design equations previously prepared are verified and found to be only applicable for medium and long columns.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.230-234
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• 2010

This study examined the effect of wall friction on deformation characteristics of the cellular bulkhead, in terms of artificial wall friction based on the results of model tests according to the existing penetration ratio and loading height. 1. The effect of wall friction on deformation characteristics of the cellular bulkhead turned out to be less as the loading height decreases and the penetration ratio increases. The yield load also becomes less as wall friction decreases. 2. The ratio of the rotational displacement to the horizontal displacement of the cellular bulkhead becomes less as the loading height decreases and the penetration ratio increases. Hence it is concluded that the effect of wall friction has close relationship with the rotational displacement.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.1-7
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• 2020

In structures excavated in rock mass, load progressively increases to a level and remains constant during the construction. Rocks display different elastic properties such as E_i and ʋ under different loading conditions and this requires to use the true values of elastic properties for the design of safe structures in rock. Also, rocks will undergo horizontal and vertical deformations depending on the amount of load applied. However, under constant loads, values of E_i and ʋ will vary in time and induce variations in the behavior of the rock mass. In some empirical equations in which deformation modulus of the rock mass is taken into consideration, elastic parameters of intact rock become functions in the equation. Hence, the use of time dependent elastic properties determined under constant loading will yield more reliable results than when only constant elastic properties are used. As well known, rock material will play an important role in the deformation mechanism since the discontinuities will be closed due to the load. In this study, E_i and ʋ values of intact rocks were investigated under different constant loads for certain rocks with high deformation capabilities. The results indicated significant time dependent variations in elastic properties under constant loading conditions. E_i value obtained from deformability test was found to be higher than the E_i value obtained from the constant loading test. This implies that when static values of elastic properties are used, the material is defined as more elastic than the rock material itself. In fact, E_i and ʋ values embedded in empirical equations are not static. Hence, this workattempts to emerge a new understanding in designing of safer structures in rock mass by numerical methods. The use of time-dependent values of E_i and ʋ under different constant loads will yield more accurate results in numerical modeling analysis.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.94-108
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• 1988

The use of geotextile as reinforcing materials in soil structures has become widespread throughout the world. Geotextile reinforcement has been used in retaining walls, roadbed, embankment stabilization and especially reinforcement of soft foundation, and so on, In the past, however, its design and construction have been performed empirically. In this study, laboratory model tests were carried out in order to investigate the effects of geotextile rein- forcement on vertical and horizontal displacement and other characteristics in soft founda- tions. The experiments were executed in eight treatments ;no geotextile between embank - ment and subsoils, and seven geotextiles with different tensile strength. And such factors as the loading conditions, the tensile strength of geotextiles, the ingredient of geotextiles and the elapsed time were investigate in this study. And the analytical method were executed in order to study the stress and behavior of geotextile - reinforced soil structure by the nonlinear elasto - plastic finite element model. The following conclusions were drawn from this study. 1. Geotextile reinforcement reduced the effects of banking loads on subsoils more effectively with the increase of their tensile strength. 2. As the tensile strength of geotextiles was increase, the rate of the initial vertical disp - lacements of loading plate was reduced inverse proportional to loads, Rowever, the effect of loading was reduced when the loads exceed a certain limits, 3. The effect of reinforcement of nonwoven geotextile was 1.5-4.5 times larger than that of the woven geotextile with equivalent tensile strength. 4. The increased bearing capacity and the reduced settlement are proportioned as the tensile strength of geotextile. 5. The settlement at the long time loading were developed almost all, were completed after 10 days and the additional settlement were not developed since then. 6. The nonlinear elasto - plastic finite element method are accurate to predict the stresses and behayior of geotextile - reinforced soil structures.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.187-197
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• 2013

PURPOSE. The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS. Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a $45^{\circ}$ angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS. In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION. This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.123-131
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• 2012

Recent earthquake records indicate that the vertical component of earthquake loading, generally neglected in seismic slope stability analysis, has a significant influence on the stability. This is particularly true for the earthquakes originating inside the continent, not from its boundaries. Therefore the design of geotechnical structures without consideration of vertical component of earthquake loading may result in unsafe design. In this study, with a consideration of the effect of vertical seismic loading, the horizontal yield seismic coefficients under various slope conditions are estimated, using the lower bound limit analysis. In addition, the equation for the determination of the critical direction (either upward or downward) of vertical seismic loading is proposed.