• Economic and Environmental Geology
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• v.46 no.6
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• pp.485-494
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• 2013

$CO_2$ Monitoring, Mitigation and Verification (MMV) is the essential part in the Carbon Capture and Storage (CCS) project in order to assure the storage permanence economically and environmentally. In large-scale CCS projects in the world, the seismic time-lapse survey is a key technology for monitoring the behavior of injected $CO_2$. In this study, we developed a basic process procedure for 3-D seismic baseline data from the Aquistore project, Estevan, Canada. Major target formations of Aquistore CCS project are the Winnipeg and the Deadwood sandstone formations located between 1,800 and 1,900 ms in traveltime. The analysis of trace energy and similarity attributes of seismic data followed by spectral decomposition are carried out for the characterization of $CO_2$ injection zone. High trace energies are concentrated in the northern part of the survey area at 1,800 ms and in the southern part at 1,850 ms in traveltime. The sandstone dominant regions are well recognized with high reflectivity by the trace energy analysis. Similarity attributes show two structural discontinuities trending the NW-SE direction at the target depth. Spectral decomposition of 5, 20 and 40 Hz frequency contents discriminated the successive E-W depositional events at the center of the research area. Additional noise rejection and stratigraphic interpretation on the baseline data followed by applying appropriate imaging technique will be helpful to investigate the differences between baseline data and multi-vintage monitor data.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.73-81
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• 2016

Recently, the construction of onshore waste landfill sites has been studied due to the increase of waste and geosynthetics are widely utilized to enforce and protect waste landfill. Geosynthetics comprises the interface with soil and the seismic behavior and stability mostly depend on the dynamic shear behavior of the geosynthetic-soil interface. Therefore, the understanding of dynamic shear behavior and dynamic relative displacement of the interface is critical. The dynamic shear behavior of the interface is affected by surrounding conditions and loading and shows very complicated response, and, it is difficult to study theoretically. In this study, laboratory test to investigate dynamic relative displacement is performed under chemical condition. Dynamic interface apparatus is utilized and cyclic simple shear tests are conducted under short term (60 days of submerging period) and long term (840 days of submerging period) conditions. Consequently, relative displacement of the interface shows the largest values under acid condition, which means more severe damage of the interface.

• Geophysics and Geophysical Exploration
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• v.21 no.3
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• pp.198-206
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• 2018

In this preliminary study, dehydration of the subducting slab and behavior of the expelled water are numerically modeled using 2-dimensional model scheme. The hydrated minerals in the oceanic crust of the subducting slab experience dehydration by increases in temperature and pressure and expel their water into the overlying mantle wedge. Behavior of the expelled water is governed by both the corner flow in the mantle wedge and porous flow of the expelled water through the pores of the mantle minerals. The effects of convergence rate and age of the subducting slab as well as grain size of the minerals on the dehydration of the subducting slab and behavior of the expelled water are evaluated. The water solubility of the oceanic crust measured from the laboratory experiments is considered for modeling dehydration of the oceanic crust. The model calculations show most of the hydrated minerals in the oceanic crust is dehydrated by a depth of 100 km and the effects of the convergence rate and age of the subducting slab on the dehydration of the subducting slab and behavior of the expelled water are not significant. The larger grain size allows faster porous flow of the expelled water through the oceanic crust, mantle wedge and overlying continental crust and reduces the volume fraction of the expelled water there. The developed technique will be used for future studies on arc volcanism and has a potential implication for the other fields such as seismic tomographic study.

• Journal of the Korean GEO-environmental Society
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• v.24 no.9
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• pp.33-40
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• 2023

The lateral load which is applied to the pile foundation supporting the superstructure during an earthquake is divided into the inertia force of the upper structure and the kinematic force of the ground. The inertia force and the kinematic force could cause failure to the pile foundation through different complex mechanisms. So it is necessary to predict and evaluate interaction of the ground-pile-structure properly for the seismic design of the foundation. The interaction is affected by the lateral behavior of the structure, the length of the pile, the boundary conditions of the head, and the relative density of the ground. Confining pressure and ground stiffness change accordingly when the relative density changes, and it results that the coefficient of subgrade reaction varies depending on each system. Horizontal bearing behavior and capacity of the pile foundation vary depending on lateral load condition and relative density of the sandy soil. Therefore, the 1g shaking table tests were conducted to confirm the effect of the relative density of the dried sandy soil to dynamic behavior of the group pile supporting the superstructure. The result shows that, as the relative density increases, maximum acceleration of the superstructure and the pile cap increases and decreases respectively, and the slope of the p-y curve of the pile decreases.

• Structural Engineering and Mechanics
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• v.47 no.4
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• pp.575-598
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• 2013

The study presents the results of an experimental program concerning the shear force transfer between reinforced concrete (RC) jackets and existing columns with damages. In order to investigate the effectiveness of the repair method applied and the contribution of each shear transfer mechanism of the interface. It includes 22 concrete columns (core) (of 24,37MPa concrete strength) with square section (150mm side, 500 mm height and scale 1:2). Ten columns had initial construction damages and twelve were subjected to initial axial load. Sixteen columns have full jacketing at all four faces with 80mm thickness (of 31,7MPa concrete strength) and contain longitudinal bars (of 500MPa nominal strength) and closed stirrups spaced at 25mm, 50mm or 100mm (of 220MPa nominal strength). Fourteen of them contain dowels at the interface between old and new concrete. All columns were subjected to repeated (pseudo-seismic) axial compression with increasing deformation cycles up to failure with or without jacketing. Two load patterns were selected to examine the difference of the behavior of columns. The effects of the initial damages, of the reinforcement of the interface (dowels) and of the confinement generated by the stirrups are investigated through axial- deformation (slip) diagrams and the energy absorbed diagrams. The results indicate that the initial damages affect the total behavior of the column and the capacity of the interface to shear mechanisms and to slip: a) the maximum bearing load of old column is decreased affecting at the same time the loading capacity of the jacketed element, b) suitable repair of initially damaged specimens increases the capacity of the jacketed column to transfer load through the interface.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.1
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• pp.53-61
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• 2014

RC shear wall sections which have irregular shapes such as T, ㄱ, ㄷ sections are typically used in low-rise buildings in Korea. Pushover analysis of building containing such members costs a lot of computation time and needs professional knowledge since it requires complicated modeling and, sometimes, fails to converge. In this study, a method using an equivalent column element for the shear wall is proposed. The equivalent column element consists of an elastic column, an inelastic rotational spring, and rigid beams. The inelastic properties of the rotational spring represent the nonlinear behavior of the shearwall and are obtained from the section analysis results and moment distribution for the member. The use of an axial force to compensate the difference in the axial deformation between the equivalent column element and the actual shear wall is also proposed. The proposed method is applied for the pushover analysis of a 5- story shear wall-frame building and the results are compared with ones using the fiber elements. The comparison shows that the inelastic behavior at the same drift was comparable. However, the performance points estimated using the pushover curves showed some deviations, which seem to be caused by the differences of estimated yield point and damping ratios.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.627-634
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• 2004

The purpose of this study is to investigate seismic performance of a bearing wall system for apartment buildings. An 1/3 scale three-story specimen was constructed and tested under cyclic lateral loads. The specimen was consisted of pierced walls and coupling elements as well as floor slabs. The bearing wall system is considered to have a adequate deformation capacity up to $2.0\%$ of roof drift ratio, and the experimental results showed the ductile load-deformation characteristics even though some walls were failed in shear Nonlinear analysis was peformed to compare the load-deformation curve obtained from the experimental program. The result of nonlinear analysis could be useful to predict the actual behavior characteristics of the bearing wall system subjected to lateral loads.

• Journal of Korean Society of Steel Construction
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• v.29 no.3
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• pp.193-204
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• 2017

Fatigue strength of temporary steels and painted structural steels corroded under outdoor atmospheric environments is not clear. In this study, fatigue tests were carried out on steel plates which were cut off from 7-year-old temporary structural member under subway construction environment and from 75-year-old Yeongdo bridge member under marine atmospheric environment. After removing corrosion production on the steel surface, 3-dimensional surface geometry of the corroded steel was measured at intervals of $1.0{\times}1.0mm$, and corrosion characteristics such as minimum, maximum and mean values of residual thicknesses were calculated. From the fatigue test and FEM analysis results, the relationship between corrosion characteristics and fatigue behavior was presented, and change in fatigue strength of the unpainted and painted steels corroded in outdoor environments was also presented.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.1-14
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• 2009

Ductility-based seismic design is strongly required for the rational and cost-effective design of RC piers, and a reliable evaluation of shear strength is indispensable for its success. Unlike the flexural behavior of RC columns, shear behavior is highly complex, due to its many effects such as size, aspect ratio, axial force, ductility and so on. To address this, many design and empirical equations have been proposed considering these effects. However, these equations show significant differences in their evaluation of the initial shear strength, and the reduction in strength with the increase of ductility. In this study, the characteristics of initial shear strength of hollow sectional columns were investigated using experiments with the parameters of aspect ratios, void ratios, web area ratios and load patterns. The test results were analyzed through a comparison with the values predicted by empirical equations. On the basis of the mechanical characteristics and test results, a new empirical equation was proposed, and its validity was assessed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4294-4301
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• 2012

The inelastic response characteristics of the standard school buildings depending on selection of hysteresis models and variable earthquakes are studied. Three earthquake records of El-centro, Santa-Monica, Taft in accordance with KBC2009 standard and four inelastic hysteresis models such as Degrading tri-linear model, Clough model, Takeda model, and Modified Takeda model are used. The inelastic response characteristics such as story shear force, story drift ratio, story displacement are reviewed. As results, El-centro earthquake shows large response in transverse direction and Santa Monica earthquake shows larger response in longitudinal direction on the contrary. Taft earthquake shows less variation of story drift ratio and story displacement for all hysteresis models and stable response.