• Structural Engineering and Mechanics
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• v.12 no.1
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• pp.51-69
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• 2001

Whereas the potential of static inelastic analysis methods is recognised in earthquake design and assessment, especially in contrast with elastic analysis under scaled forces, they have inherent shortcomings. In this paper, critical issues in the application of inelastic static (pushover) analysis are discussed and their effect on the obtained results appraised. Areas of possible developments that would render the method more applicable to the prediction of dynamic response are explored. New developments towards a fully adaptive pushover method accounting for spread of inelasticity, geometric nonlinearity, full multi-modal, spectral amplification and period elongation, within a framework of fibre modelling of materials, are discussed and preliminary results are given. These developments lead to static analysis results that are closer than ever to inelastic time-history analysis. It is concluded that there is great scope for improvements of this simple and powerful technique that would increase confidence in its employment as the primary tool for seismic analysis in practice.

• Journal of the Korean GEO-environmental Society
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• v.25 no.11
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• pp.45-53
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• 2024

In the current work, finite difference analysis was conducted by investigating the influence of dynamic analysis, considering effective stress, on the dynamic response of composite breakwaters. For comparison, the seismic behavior of breakwaters during the Kobe earthquake was analyzed, and performance-based seismic design was validated through centrifuge model test data, accompanied by a parametric study. The composite breakwaters damaged by the Kobe earthquake were verified through numerical analysis based on effective stress analysis, and validation of both centrifuge model tests and numerical analysis methods was conducted. The results of numerical analysis confirmed the seismic resistance based on the performance-based. And the results of analysis identified similar vertical displacement and liquefaction have confirmed through excess pore pressures. Also this study was conducted on the based on performance-based seismic deign, focusing on the results of acceleration, displacement, pore pressure, and liquefaction. Therefore the purpose of this study is to verify the results of pore pressure and liquefaction through the application and non-application of Finn model to compare the determination of liquefaction by the effective stress analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.23-32
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• 2005

Torsional behavior of eccentric structure under seismic leading may cause the stress and/or deformation concentration, which arouse the failure of the structure in an unexpected manner. This study suggests D-R relationship which shows the overall displacement and rotation of the system based on the ultimate displacement capacity of the each lateral load resistant member. Using the suggested D-R relationship and displacement spectrum, the seismic assessment is conducted and verified in comparison with the time history analysis result. Multi-level seismic assessment Is considered which takes multiple seismic hazard levels and respective performance levels into account. Finally, based on the seismic assessment result, seismic rehabilitation process is presented. In this research, two rehabilitation methods are considered. One is done by means of stiffening/strengthening the seismic resistant members, and the other is based on the member ductility. Especially, in the first method, to optimize the rehabilitation result, the rehabilitation problem is modeled as an optimization problem, and solved using BFGS quasi-Newton optimization method.

• Structural Engineering and Mechanics
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• v.10 no.4
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• pp.405-426
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• 2000

Two approximate methods based on mechanism analysis suitable for seismic assessment/design of structural concrete are reviewed. The methods involve use of equal energy concept or equal displacement concept along with appropriate patterns of inelastic deformations to relate structure's maximum lateral displacement to member and plastic deformations. One of these methods (Clough's method), defined here as a ductility-based approach, is examined in detail and a modification for its improvement is suggested. The modification is based on estimation of maximum inelastic displacement using inelastic design response spectra (IDRS) as an alternative to using equal energy concept. The IDRS for demand displacement ductilities are developed for a single degree of freedom model subjected to several accelerograms as functions of response modification factor (R), damping ratios, and strain hardening. The suggested revised methodology involves estimation of R as the ratio of elastic strength demand to code level demand, and determination of design base shear using $R_{design}{\leq}R$ and maximum displacement, determination of plastic displacement using IDRS and subsequent local plastic deformations. The methodology is demonstrated for the case of a 10-story precast wall panel building.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.971-976
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• 2001

Numerical studies were performed to investigate the seismic performance of Flat Plate System. For the numerical studies, a computer program for Finite Element analysis was developed. Parametric studies were performed to investigate variations of strength and ductility of flat plate with major parameters: gravity load, reinforcement ratio, thickness, column sizes. The numerical results provide a valuable insights on the behavior of flat plates. The comparison with the current design method shows that the current design methods for strength and ductility need to be improved in some aspects.

• Journal of the Korean Geotechnical Society
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• v.38 no.9
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• pp.5-17
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• 2022

Recently, several studies have been conducted on virtual fixed-point and elastic soil spring methods to simulate the soil-pile interaction in response to spectrum analysis of pile-supported structures. However, the soil spring stiffness has not been properly considered due to the seismic load magnitude, and studies on the response spectrum analysis of pile-supported structures considering this circumstance are inadequate. Therefore, in this study, the response spectrum analysis was performed considering the soil spring stiffness according to the seismic load magnitude, and the dynamic behavior of the pile-supported structure was evaluated by comparing it with existing virtual fixed-point and elastic soil spring methods. Comparing the experiment and analysis, the moment differences occurred up to 117% and 21% in the virtual fixed-point and elastic soil spring models, respectively. Moreover, when the analysis was performed using an API p-y curve considering the soil spring stiffness according to the seismic load magnitude, the moment difference between the experiment and analysis was derived at a maximum of < 4%, and it is the most accurate method to simulate the experimental model response.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.3
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• pp.249-257
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• 2005

There are basically two methods for the seismic design of underground structures ; analytical or pseudo-static, and dynamical method. In pseudo-static analysis approach, the ground deformations are imposed as a static load and soil-structure interaction does not include dynamic or wave propagation effects. However the behavior of soil structure interaction is nonlinear, it needs to consider nonlinear soil-structure interaction effects. In this study simplified seismic analysis method to consider soil-structure interaction by iterative procedure is proposed and the results are compared and analyzed by a finite difference computer program.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.81-89
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• 2020

As the damage caused by earthquakes gradually increases, seismic retrofitting for existing public facilities has been implemented in Korea. Several types of structural analysis methods can be used to evaluate the seismic performance of structures. Among them, for nonlinear dynamic analysis, the hysteresis model must be carefully applied because it can significantly affect the behavior. In order to find a hysteresis model that predicts rational behavior, this study compared the experimental results and analysis results of the existing non-seismic reinforced concrete frames. For energy dissipation, the results were close to the experimental values in the order of Pivot, Concrete, Degrading, and Takeda models. The Concrete model underestimated the energy dissipation due to excessive pinching. In contrast, the other ones except the Pivot model showed the opposite results with relatively little pinching. In the load-displacement curves, the experimental and analysis results tended to be more similar when the column axial force was applied to columns.

• Structural Monitoring and Maintenance
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• v.11 no.3
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• pp.235-246
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• 2024

Structural seismic tests usually need to simulate the gravity load borne by the structure, the gravity load application devices should keep the force value and direction unchanged, and can adapt to the structural deformation. At present, there are two main ways to simulate gravity load in laboratory: roller group and prestress. However, there are few differential analysis between these two ways in the existing experimental studies. In this paper, the simulation software ABAQUS is used to simulate the static pushover analysis of reinforced concrete column and frame, which are the most common models in structural seismic tests. The results show that the horizontal restoring force of the model using prestressed loading method is significantly greater than roller group, and the difference between the two will increase with the increase of the horizontal deformation. The reason for the difference is that the prestressed loading method does not take the adverse effects of gravity second-order effect (P-Delta effect) into account. Therefore, the restoring force obtained under prestressed loading method should be corrected and the additional shear force caused by P-Delta effect should be deducted. After correction, the difference of restoring force between the two gravity load application methods is significantly reduced (when storey-drift is 1/550, the relative error is within 1%; and when storey-drift is 1/50, the relative error is about 3%). The research results of this research can provide reference for the selection and data processing of gravity load simulation devices in structural seismic tests.

• Journal of the Korean Geotechnical Society
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• v.39 no.9
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• pp.35-50
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• 2023

A preliminary study is conducted to develop seismic design guidelines for temporary retaining structures in a deep excavation. The study involved a comprehensive literature review of the seismic design standards applied domestically and internationally, as well as various methods to calculate seismic earth pressure for pseudostatic analysis. The FLAC 2D, a two-dimensional finite difference analysis program, was utilized to perform pseudostatic analysis using the Semirigid pressure method, Wood method, and Mononobe-Okabe method. The resulting analysis data for the wall moment and axial force of the strut were compared with the dynamic analysis outcomes to evaluate the applicability of pseudostatic analysis. The Semirigid pressure method predicted the most reasonable moment for Stiff walls experiencing horizontal displacements up to 0.4%H. Predicting the axial force of the strut exactly was challenging because the pseudostatic analysis cannot consider dynamic soil-structure interaction; however, it is deemed available for conservative preliminary review to ensure safety.