• Geomechanics and Engineering
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• v.3 no.4
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• pp.291-321
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• 2011

The paper describes a simple numerical FLAC model that was developed to simulate the dynamic response of two instrumented reduced-scale model reinforced soil walls constructed on a 1-g shaking table. The models were 1 m high by 1.4 m wide by 2.4 m long and were constructed with a uniform size sand backfill, a polymeric geogrid reinforcement material with appropriately scaled stiffness, and a structural full-height rigid panel facing. The wall toe was constructed to simulate a perfectly hinged toe (i.e. toe allowed to rotate only) in one model and an idealized sliding toe (i.e. toe allowed to rotate and slide horizontally) in the other. Physical and numerical models were subjected to the same stepped amplitude sinusoidal base acceleration record. The material properties of the component materials (e.g. backfill and reinforcement) were determined from independent laboratory testing (reinforcement) and by back-fitting results of a numerical FLAC model for direct shear box testing to the corresponding physical test results. A simple elastic-plastic model with Mohr-Coulomb failure criterion for the sand was judged to give satisfactory agreement with measured wall results. The numerical results are also compared to closed-form solutions for reinforcement loads. In most cases predicted and closed-form solutions fall within the accuracy of measured loads based on ${\pm}1$ standard deviation applied to physical measurements. The paper summarizes important lessons learned and implications to the seismic design and performance of geosynthetic reinforced soil walls.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.1
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• pp.79-91
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• 2012

A curved fiber reinforced polymer (FRP) panel is produced with a certain width depending on allowances of manufacturing processes and facilities. An targeted arch-shaped structure could be built by sequential connection of series of the FRP panels. The connection manner between the FRP panels could be given by chemical treatment, mechanical treatment and hybrid method. Among those, the connection between the panels by chemical treatment is commonly adopted. Therefore, For an optimized design of the connected part between FRP pannels, a number of direct shear tests have been undertaken in terms of a number of parameters: surface treatment conditions, bonding materials, etc.. As results, surface grinding condition by sand paper or surface treatment by sand blasting appear properly acceptable methods, and epoxy and acryl resins are shown to be effective bonding materials for the purpose in this study.

• KSBB Journal
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• v.31 no.4
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• pp.284-290
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• 2016

In this research, recombinant human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig) was produced by transgenic rice cells. RAmy3D promoter was used for overcome the limitation of low expression level in transgenic plant cells, and the secretion of target protein was accomplished by signal peptide. However, the RAmy3D promoter system which can be induced only by sugar starvation causes the decrease of cell viability. As a result, cell death promotes the release of protease which degrades the target proteins. The protein stability and productivity can be significantly influenced by proteolysis activity. Therefore, development of new strategies are necessary for the in situ recovery of target proteins from cell culture media. In this study, in situ recovery was performed by various strategies. Direct addition of Protein A resin with nylon bag leads to cell death by increased shear stress and decrease in production of hCTLA4Ig by protease. Medium exchange through modified flask could recover hCTLA4Ig with high cell viability and low protease activity, on the other hand, the productivity was lower than that of control. When in situ recovery was conducted at day 7 after induction in air-lift bioreactor, 1.94-fold of hCTLA4Ig could be recovered compared to control culture without in situ recovery. Consequently, in situ recovery of hCTLA4Ig from transgenic rice cell culture could enhance productivity significantly and prevent degradation of target proteins effectively.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1045-1075
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• 2016

Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.393-405
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• 2019

This paper evaluates the geotechnical and geo-engineering properties of the South Pars Zone (SPZ) marls in Assalouyeh, Iran. These marly beds mostly belong to the Aghajari and Mishan formations which entail the gray, cream, black, green, dark red and pink types. Marls can be observed as rock (soft rock) or soil. Marlstone outcrops show a relatively rapid change to soils in the presence of weathering. To geotechnically characterise the marls, field and laboratory experiments such as particle-size distribution, hydrometer, Atterberg limits, uniaxial compression, laboratory direct-shear, durability and carbonate content tests have been performed on soil and rock samples to investigate the physico-mechanical properties and behaviour of the SPZ marls in order to establish empirical relations between the geo-engineering features of the marls. Based on the experiments conducted on marly soils, the USCS classes of the marls is CL to CH which has a LL ranging from 32 to 57% and PL ranging from 18 to 27%. Mineralogical analyses of the samples revealed that the major clay minerals of the marls belong to the smectite or illite groups with low to moderate swelling activities. The geomechanical investigations revealed that the SPZ marls are classified as argillaceous lime, calcareous marl and marlstone (based on the carbonate content) which show variations in the geomechanical properties (i.e., with a cohesion ranging from 97 to 320 kPa and a friction angle ranging from 16 to 35 degrees). The results of the durability tests revealed that the degradation potential showed a wide variation from none to fully disintegrated. According to the results of the experiments, the studied marls have been classified as calcareous marl, marlstone and argillaceous lime due to the variations in the carbonate and clay contents. The results have shown that an increase in the carbonate content leads to a decrease in the degradation potential and an increase in the density and strength parameters such as durability and compressive strength. A comparison of the empirical relationships obtained from the regression analyses with similar studies revealed that the results obtained herein are reasonably reliable.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.25-34
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• 2003

Recently, performance-based analysis/design methods such as the capacity spectrum method and the direct displacement-based design method were developed. In these methods, estimation of energy dissipation capacity of RC structures depends on empirical equations which are not sufficiently accurate, On the other hand, in a recent study, a simplified method for evaluating energy dissipation capacity was developed. In the present study, based on the evaluation method, a new seismic design method for flexure-dominated RC walls was developed. In determination of earthquake load, the proposed design method can address variations of energy dissipation capacity with design parameters such as dimensions and shapes of cross-sections, axial force, and reinforcement ratio and arrangement, The proposed design method was compared with the current performance-based design methods. The applicability of the proposed method was discussed.

• Geotechnical Engineering
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• v.12 no.5
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• pp.137-154
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• 1996

Pull-out tests for three different types of strip reinforcements are performed to investigate variation of the apparent coefficient of friction which occurs between the reinforcements and the weathered granite soils with different contents of fine materials. The contents of fine materials for the soil sample are varied from 7% to 36% and the reinforcements used for the pullout tests are smooth, ribbed steel strips and a textured shape Paraweb 1 Friction tie. Test results show that the apparent coefficient of friction tends to decrease with the increase of the content of fine meterials. It is known, however, that the minimum apparent coefficient of friction required to the design of reinforced earth structures can be achieved even at 35% fine contents by using appropriate reinforcements. The ribbed strip reinforcement is found to be the most effective in mobilizing the apparent friction when interacting to finer weathered granite soils. The textured reinforcement is also useful for 35% fine con tents if the textured depth is increased.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.291-302
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• 2018

Rigid body spring method (RBSM) is an effective tool to simulate the cracking process of structures, and has been successfully applied to investigate the behavior of reinforced concrete (RC) members. However, the theoretical researches and engineering applications of this method mainly focus on two-dimensional problems as yet, which greatly limits its applications in actual engineering projects. In this study, a three-dimensional (3-D) RBSM for RC structures is proposed. In the proposed model, concrete, reinforcing steels, and their interfaces are represented as discrete entities. Concrete is partitioned into a collection of rigid blocks and a uniform distribution of normal and tangential springs is defined along their boundaries to reflect its material properties. Reinforcement is modeled as a series of bar elements which can be freely positioned in the structural domain and irrespective of the mesh geometry of concrete. The bond-slip characteristics between reinforcing steel and concrete are also considered by introducing special linkage elements. The applicability and effectiveness of the proposed method is firstly confirmed by an elastic T-shape beam, and then it is applied to analyze the failure processes of a Z-type component under direct shear loading and a RC beam under two-point loading.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.1
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• pp.82-95
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• 1989

This study was carried out for the stability analysis of earth dam by the variation of compaction density. The test samples were taken from five kinds of soil used for banking material and the degree of compaction for this samples were chosen 100, 95, 90, 85, and 80 percent. The stability problems were analysed by the settlement and camber( extra banking) of dam, strength parameter and dam slope, and coefficient of permeability and seapage flow through dam body. The results of the stability analysis of earth dam are as follows. 1. The more the fine particle increases and lower the compaction degree becomes, the lower the preconsolidation load becomes but the compression index becomes higher. 2. Sixty to eighty percent of settlement of dam occurs during the construction period and the settlement ratio after completion of dam is inversly proportional to the degree of compaction. 3. The camber of dam has heigher value in condition that it has more fine particle(N) and heigher dam height(H) with the relation of H= e(aN-bH-e). 4. The cohesion(C) decreases in proportion to compaction degree(D) and fine particle(N) with the relation of C= aD+ bN-c, but the internal friction angle is almost constant regardless of change of degree of compaction. 5. In fine soil, strength parameter from triaxial compression test is smaller than that from direct shear test but, they are almost same in coarse soil regardless of the test method. 6. The safety factor of the dam slope generally decreases in proportion to cohesion and degree of compaction but, in case of coarse soil, it is less related to the degree of compaction and is mainly afected by internal friction angle. 7. Soil permeability(K) decreases by the increases of the degree of compaction and fine particle with relation of K=e(a-bl)-cN) 8. The more compaction thickness is, the less vertical permeability (Kv) is but the more h6rzontal permeability (KH) is, and ratio of Kv versus KH is largest in range from 85 to 90 percent of degree of corn paction. 9. With the compaction more than 85 percent and coefficient of permeability less than ${\alpha}$X 10-$^3$cm/sec, the earth dam is generally safe from the piping action.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.545-554
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• 2007

Landslides is mainly induced by a heavy rainfall, earthquake ground motion, and some other factors like soil mechanics, morphological-geological factors etc. Since the starting point of the failure seemed to be originated at a construction site in the study, it is meaningful to find out the relationship between the landslide and the construction. For this study, the slope failure factor was examined carefully to see that the original natural slope had vulnerability and that the complex ground had unstability changed by construction. A field survey was conducted on the original ground surface and filled-up ground. A laboratory test was also conducted to determine the geomechanical properties of soil samples. 2D and 3D limit equilibrium analysis with changing groundwater level were conducted at the failure depth using a seismic refraction survey. The result shows that the factor of safety is similar stability under all condition, but unstable under saturated condition.