• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.11-23
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• 2006

This paper evaluates the seismic response of multi-span prestressed concrete girder bridges typically found in the New Madrid Seismic Zone region of the central United States. Using detailed nonlinear analytical models and synthetic ground motion records for Memphis, TN, nonlinear response history analyses are performed for two levels of ground motion: 10% probability of exceedance (PE) in 50 years, and 2% probability of exceedance (PE) in 50 years. The results show that the bridge performance is very good fur the 10% PE in 50 years ground motion level. However, the performance for the 2% PE in 50 years ground motion is not so good because it results in highly inelastic behavior of the bridge. Impact between decks results in large ductility demands on the columns, and failure of the bearings that support the girders. It is found that making the superstructure continuous, which is commonly performed for reducing dead load moments and maintenance requirements, results in significant improvement in the seismic response of prestressed concrete girder bridges.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.401-419
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• 1997

In this paper the kinematics of damage for finite strain, elasto-plastic deformation is introduced using the fourth-order damage effect tensor through the concept of the effective stress within the framework of continuum damage mechanics. In the absence of the kinematic description of damage deformation leads one to adopt one of the following two different hypotheses for the small deformation problems. One uses either the hypothesis of strain equivalence or the hypotheses of energy equivalence in order to characterize the damage of the material. The proposed approach in this work provides a general description of kinematics of damage applicable to finite strains. This is accomplished by directly considering the kinematics of the deformation field and furthermore it is not confined to small strains as in the case of the strain equivalence or the strain equivalence approaches. In this work, the damage is described kinematically in both the elastic domain and plastic domain using the fourth order damage effect tensor which is a function of the second-order damage tensor. The damage effect tensor is explicitly characterized in terms of a kinematic measurure of damage through a second-order damage tensor. Two kinds of second-order damage tensor representations are used in this work with respect to two reference configurations.

• Journal of the Korean GEO-environmental Society
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• v.20 no.12
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• pp.5-14
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• 2019

Recently in Korea, researches on seismic analyses for high-rise buildings in a large city have been increasing because earthquakes have occurred. However, the ground conditions are not included in most of seismic researches and analyses on a high-rise building. Also the influence of the predominant period of a seismic wave is not considered in reality. Therefore, in this study, the influence of the predominant period of a seismic wave on the dynamic behavior of high-rise buildings was analyzed based on the complete system model which can consider the grounds. For this purpose, 2D dynamic analyses based on a linear time history analysis were performed using MIDAS GTS NX, a finite-element based program. Dynamic behavior was analyzed in terms of horizontal displacements, drift ratios, bending stresses, and building weak zones. As a result, in overall, the dynamic response of a high-rise building become bigger as the predominant period of a seismic wave become longer. It was also found that the predominant period had a greater influence than other parameters, ground conditions and peak ground acceleration.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.141-150
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• 2009

When constructing a subsea tunnel in discontinuous rock mass, fluid flow in joints has a great influence on the behavior of the tunnel so that hydro-mechanical coupled analysis should be performed for the stability estimation. In practice, relaxed rock load is generally used for the design of tunnel concrete lining. In a continuum analysis, a method based on the distribution of local safety factor around a tunnel was proposed for the estimation of a potential relaxed zone. However, in the case of discontinuous rock mass in which joints are developed, the whole stability of tunnels depends on the behavior of the joints. In this study, therefore, a method is proposed for the estimation of a potential relaxed zone occurred by the excavation of a tunnel in discontinuous rock mass. The suggested method is validated by sensitivity analysis and the comparison with the results of continuum analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.823-832
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• 2006

To ensure the serviceability requirements of PSC composite girder bridges, it is essential to predict the stresses and deformations of the structure under service load conditions. Stresses and deformations vary continuously with time due to the effects of creep and shrinkage of concrete and relaxation of prestressing steel. The importance of these time-dependent effects is much more pronounced in precast prestressed concrete structures built in stages than in those constructed in one operation. In this paper, time-dependent analyses for PSC composite bridges using 30m standard girders have been conducted considering with the variation of the times of introducing initial prestressing forces and casting concrete. A computer program has been developed for the time-dependent analysis of simple or continuous PSC composite girders and parametric studies are conducted. Based on the numerical results, it is investigated the long-term behaviors of PSC composite girder bridges and discussed the limitations of the current codes for the prestress loss.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.125-132
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• 2020

Embedded joints in the rock mass are a major constituent influencing its mechanical behavior. Numerical analysis requires a rigorous modeling methodology for the rock mass with detailed information regarding joint properties, orientation, spacing, and persistence. This paper provides a mechanical model for a jointed rock mass based on the implicit joint-continuum approach. Stiffness tensors for rock mass are evaluated for an assemblage of intact rock separated by sets of joint planes. It is a linear summation of compliance of each joint sets and intact rock in the serial stiffness system. In the application example, kinematic analysis for a planar failure of rock slope is comparable with empirical daylight envelope and its lateral limits. Since the developed implicit joint-continuity model is formulated on a continuum basis, it will be a major tool for the numerical simulations adopting published plenteous thermal-hydro-chemical experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.25-35
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• 2003

Scale model tests were performed to investigate the seismic behavior of the solid and hollow rectangular RC piers with 50% of lap-spliced longitudinal bars in plastic hinge regions. Continuous bars and lap-spliced ones with a lap length of 39 times the bar diameter were arranged alternately in the sections. In order to clarify the influence of lap splice on a ductility the effect of axial force and lateral confinement were excluded in the test. The typical flexural failure conducting a ductile behavior were observed in both models. It is confirmed that the 50% of lap-spliced bars can be considered as an alternative of seismic detailing for longitudinal bars.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.233-251
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• 1998

This paper deals with the prediction of behavior of composite girder bridges according to the placing sequences of concrete deck. Based on a degenerate kernel of compliance function in the form of Dirichlet series, the time-dependent behaviors of bridges are simulated, and the layer approach is adopted to determine the equilibrium condition in a section. The variation of bending moments along the bridge length caused by the slab casting sequence is reviewed and correlation studies between section types and placing sequences are conducted with the objective to establish the validity of the continuous placing of concrete deck on the closed steel box-girder which is broadly used in practice.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.27-37
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• 2001

본 연구에서는 지금까지 수행한 건조토 지반에 대한 말뚝의 수평거동 연구의 연속된 연구로서 지반내에 함수비가 존재하는 포화토 및 습윤토 지반에서의 수평거동에 대한 지반내 함수비의 영향성을 평가하고자 함이 목적이다. 말뚝의 수평거동을 고찰하기 위하여 각각 다른 함수비를 갖는 네 종류의 지반과 말뚝의 두부 및 선단 구속조건이 다른 네 종류의 말뚝조건으로 모형실험을 수행하였다. 본 연구에서 1회의 지하수 상승과 하강을 반복하는 모형실험결과에 의하면, 포화토와 습윤토 지반의 수평지지력은 건조토 지반에 비하여 각각 26%~45% 감소와 20%~36%정도 증가하는 것으로 나타났다. 말뚝두부 고정과 선단 자유조건의 경우, 동일 수평변위 1mm에서의 최대 휨모멘트는 건조토 지반에 비하여 25%의 함수비를 갖는 습윤토 지반에서 약 48% 증가하나, 34.06%의 함수비를 갖는 포화토 지반에서는 반대로 68% 감소하였다. 이는 지하수의 존재로 인한 입자간 인력에 의한 유효응력과 겉보기강도의 증가 그리고 단위중량의 증가로 설명할 수가 있다. 지속수평하중에 대한 수평변위와 최대 휨모멘트의 변화를 포화토 및 습윤토 지반에서 관찰할 수 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.413-419
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• 2011

The nano-size hoenycomb structures have the higher ratio of the surface to the volume than macro-size honeycomb structures, and they can maximize the functionality of the electrical and chemical catalyst. The mechanical behaviors of the nano-sized structures are different from ones of the macro-size structure, and it is caused by the surface effect. This surface effect can be investigated by the atomistic simulation; however, the prediction of mechanical behaviors of the nano-sized honeycombs are practically impossible due to excessive computational resources and computation time. In this paper, by combining the bridging method considering the surface stress elasticity model with homogenization method, the mechanical behaviors of the nano-sized honeycombs are predicted efficiently.