• Geomechanics and Engineering
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• v.10 no.5
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• pp.657-676
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• 2016

In this paper, the active lateral earth pressure is evaluated using the stress characteristics or slip line method. The lateral earth pressure is expressed as the lateral earth pressure coefficients due to the surcharge, the unit weight and cohesion of the backfill soil. Seismic horizontal and vertical pseudo-static coefficients are used to consider the seismic effects. The equilibrium equations along the characteristics lines are solved by the finite difference method. The slope of the ground surface, the wall angle and the adhesion and friction angle of the soil-wall interface are also considered in the analysis. A computer code is provided for the analysis. The code is capable of solving the characteristics network, determining active lateral earth pressure distribution and calculating active lateral earth pressure coefficients. Closed-form solutions are provided for the lateral earth pressure coefficients due to the surcharge and cohesion. The results of this study have a good agreement with other reported results. The effects of the geometry of the retaining wall, the soil and soil-wall interface parameters are evaluated. Non-dimensional graphs are presented for the active lateral earth pressure coefficients.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.34-41
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• 2011

Wrought nickel-base superalloys are being considered as the structural materials in very-high temperature gas-cooled reactors. To understand the effects of impurities, especially oxygen, in helium coolant on the mechanical properties of Alloy 617, creep tests were performed in high temperature flowing He environments with varying $O_2$ contents at 800, 900, and $1000^{\circ}C$. Also, creep life in static He was measured to simulate the pseudo-inert environment. Creep life was the longest in static He, while the shortest in flowing helium. In static He, impurities like $O_2$ and moisture were quickly consumed by oxidation in the early stage of creep test, which prevented further oxidation during creep test. Without oxidation, microstructural change detrimental to creep such as decarburization and internal oxidation were prevented, which resulted in longer creep life. On the other hand, in flowing He environment, surface oxides were not stable enough to act as diffusion barriers for oxidation. Therefore, extensive decarburization and internal oxidation under tensile load contributed to premature failure resulting in short creep life. Limited test in flowing He+200ppm $O_2$ resulted in even shorter creep life. The oxidation samples showed extensive spallation which resulted in severe decarburization and internal oxidation in those environments. Further test and analysis are underway to clarify the relationship between oxidation and creep resistance.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.3
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• pp.9-21
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• 2012

Concrete filled steel tube (CFT) columns have been widely used in moment resisting frame structures both in seismic zones. This paper discusses the design of such members based on the advanced methods introduced in the 2005 AISC Specification and the 2005 Seismic Provisions. This study focuses particularly on design following both linear and nonlinear methods utilizing equivalent static and dynamic loads for low-rise moment frames. The paper begins with an examination of the significance of pseudo-elastic design interaction equations and the plastic ductility demand ratios due to combined axial compressive force and bending moment in CFT members. Based on advanced computational simulations for a series of five-story composite moment frames, this paper then investigates both building performance and new techniques to evaluate building damage during a strong earthquake. It is shown that 2D equivalent static analyses can provide good design approximations to the force distributions in moment frames subjected to large inelastic lateral loads. Dynamic analyses utilizing strong ground motions generally produce higher strength ratios than those from equivalent static analyses, but on more localized basis. In addition, ductility ratios obtained from the nonlinear dynamic analysis are sufficient to detect which CFT columns undergo significant deformations.

• Earthquakes and Structures
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• v.15 no.6
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• pp.687-699
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• 2018

This paper investigates the pseudo-static analysis of reinforced slopes with geosynthetics under the influence of the uniform surcharge to evaluate the maximum tensile force of reinforcements. The analytical approach has basically been used to develop the new practical procedure to estimate both tensile force and its distribution in the height of the slope. The base of developed relationships has been adapted from the conventional horizontal slice method. The limit equilibrium framework and the assumptions of log-spiral failure surface have directly been used for proposed analytical approach. A new analytical approach considering a single layer of non-cohesion soil and the influence of uniform surcharge has been extracted from the 5n equation and 5n unknown parameters. Results of the proposed method illustrated that the location of the surcharge, amount of internal friction and the seismic coefficient have the remarkable effect on the tensile force of reinforcement and might be 2 times increasing on it. Furthermore, outcomes show that the amount of tensile force has directly until 2 times related to the amount of slope angle and its height range. Likewise, it is observed that the highest value of the tensile force in case of slope degree more than 60-degree is observed on the lower layers. While in case of less degree the highest amount of tensile force has been reported on the middle layers and extremely depended to the seismic coefficient. Hence, it has been shown that the tensile force has increased more than 6 times compared with the static condition. The obtained results of the developed procedure were compared with the outcomes of the previous research. A good agreement has been illustrated between the amount results of developed relationships and outcomes of previous research. Maximum 20 and 25 percent difference have been reported in cases of static and seismic condition respectively.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.451-458
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• 2008

The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.403-406
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• 1999

Although infilled wall considered as a non-structural element, the infilled applied in reinforced concrete frame structural systems represents an important element influencing the behaviour and the stability of a structure under seismic effect. This research is performed an experimental investigation of gravity-load designed single-stroy, single-bay, low-rise nonseismic moment-resisting reinforced concrete frame 2 dimension specimens to evaluate the effect of seismic capacity. For pseudo static test, it was manufactured one half scale specimens of two types (Bare Frame, Infilled Frame) based on typical building. The results of these experiments provided regarding the global as well as the local responses of 1) Crack pattern and failure modes, 2) Stiffness, strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.453-456
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• 2003

This research is to evaluate the seismic performance of reinforced concrete bridge piers with lap-spliced longitudinal reinforcement steels in the plastic hinge region, and to develop the enhancement scheme of their seismic capacity. Six circular columns of 0.6m diameter and 1.5m height were made with two confinement steel ratios. They were damaged under series of artificial earthquakes that could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under an axial load, P=$0.1f_{ck}A_{g}$, and residual seismic performance of damaged columns was evaluated. Test results show that RC bridge piers with lap-spliced longitudinal steels behaved with minor damage even under artificial earthquakes with 0.22g PGA, but failed at low ductility subjected to the subsequent quasi-static load test. This failure was due to the debonding of the lap splice. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region showed significant improvement both in flexural strength and displacement ductility.

• Structural Engineering and Mechanics
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• v.9 no.2
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• pp.111-126
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• 2000

Truss type structures are attractive to a variety of engineering applications on earth as well as in space due to their high stiffness to mass ratios and ease of construction and fabrication. During the service life, an individual member of a truss structure may lose load carrying capacity due to many reasons, which may lead to collapse of the structure. An analytical and computational procedure has been developed to study the response of truss structures subject to member failure under static and dynamic loadings. Emphasis is given to the dynamic effects of member failure and the propagation of local damage to other parts of the structure. The methodology developed is based on nonlinear finite element analysis technique and considers elasto-plastic material nonlinearity, postbuckling of members, and large deformation geometric nonlinearity. The pseudo force approach is used to represent the member failure. Results obtained for a planar nine-bay indeterminate truss undergoing sequential member failure show that failure of one member can initiate failure of several members in the structure.

• Geomechanics and Engineering
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• v.4 no.3
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• pp.209-218
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• 2012

This paper presents the derivation of an analytical expression for the dynamic active thrust from c-${\phi}$ (c = cohesion, ${\phi}$ = angle of shearing resistance) soil backfill on rigid retaining walls with wall friction and adhesion. The derivation uses the pseudo-static approach considering tension cracks in the backfill, a uniform surcharge on the backfill, and horizontal and vertical seismic loadings. The development of an explicit analytical expression for the critical inclination of the failure plane within the soil backfill is described. It is shown that the analytical expression gives the same results for simpler special cases previously reported in the literature.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.935-938
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• 1999

메모리 테스트는 Built-In Self Test(BIST)와 같이 메모리에 내장된 회로를 통하여 자체 점검하는 방법과 테스터를 통하여 생성된 패턴을 주입하는 방법이 있다. 테스트 패턴 생성방법으로는 각각의 고장모델에 대한 테스트 패턴을 deterministic하게 생성해주는 방법과 Pseudo Random Pattern Generator(PRPG)를 이용하여 생성하는 경우로 구분할 수 있다. 본 연구에서는 PRPG를 패턴 생성기로 사용하여 여러 가지 메모리의 결함을 대표한다고 볼 수 있는 Static 및 Dynamic Neighborhood Pattern Sensitive Fault(NPSF) 등 다양한 종류의 고장을 점검할 수 있도록 메모리 BIST를 구성하였다. 기존의 Linear Feedback Shift Register(LFSR)보다 본 연구에서 제안하는 Linear Hybrid Cellular Automata(LHCA)를 이용한 PRPG가 높고 안정된 고장 점검도를 나타내었다.