• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.949-960
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• 2002

Flat plate structures under lateral load are susceptible to punching shear failure of the slab-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, due to complexity in the behavior and difficulty in simulating the actual load and boundary conditions of the flat plate system, it is not easy to obtain reliable data regarding to the strength and ductility from the previous experimental studies. In the present study, a numerical study was performed for interior connections of continuous flat plate. For the purpose, a computer program for nonlinear FE analyses was developed, and the validity was verified by comparisons with the existing experimental results. Through the parametric studies, the variations of bending moment, shear, and torsional moment around the connection were investigated. Based on the findings of the numerical studies, the aspects which need to be improved in current design methods were discussed. The results of the present study will be used for developing a design method for the flat plate-column connection in the companion paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.37-48
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• 2010

The seismic control effect of reinforced concrete structures with low energy dissipating capacity due to stiffness degradation is investigated through nonlinear time history analysis. The primary structure is idealized as a SDOF system of modified Takeda hysteresis rule and an elasto-perfectly-plastic nonlinear spring is added to represent a hysteretic damping device. Based on statistics of the numerical analysis, equivalent linearization techniques are evaluated, and empirical equations for response prediction are proposed. As a result, estimation of the ductility demand with proposed empirical equations is more desirable than the equivalent linearization techniques. The optimal yield strengths based on empirical equations are significantly different from the optimal yield strength of elasto-perfectly-plastic systems. Also, the results indicate that the reduction effect of the ductility demand is more remarkable for smaller natural periods.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.469-475
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• 2016

As we are facing the shortage of oil energy, studies on renewable energy, wind energy research has been naturally getting attention. Among wind energies, ocean wind energy is relatively abundant compared to land wind energy and therefore, is getting much attention in terms of its efficiency. However, the problem is the cost. Generally, the cost ratio of the supporting structure is over 25% of the total installation cost of a offshore wind turbine system. Thus, it is very important to reduce the total installation cost of the offshore wind turbine and develop accurate analysis methodology for various offshore wind turbine foundations. In this study, nonlinear structure-soil interaction analyses have been proposed and conducted for the typical suction bucket model of an offshore wind turbine foundation, and the results were compared with experimental test data for numerical validations.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.961-972
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• 2002

Flat plate structures under lateral load are susceptible to the brittle shear failure of plate-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, according to previous studies, current design methods do not accurately estimate the strength of plate-column connection. In the present study, parametric study using nonlinear finite element analysis was performed for interior connections. Based on the numerical results, a design method for the connection was developed. At the critical sections around the connection coexist flexural moment and shear developed by lateral and gravity loads, and maximum allowable eccentric shear stresses were proposed based on the interactions between the flexural moment and shear, The proposed method can precisely predict the strength of the connection, compared with the current design provisions. The predictability of the proposed method was verified by the comparisons with existing experiments and nonlinear numerical analyses.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.566-577
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• 2002

As advanced earthquake analysis/design methods such as the nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and capacity of energy dissipation. However, currently, estimation of energy dissipation depends on empirical equations that are not sufficiently accurate, or experiment and sophisticated numerical analysis which are difficult to use in practice.0 the present study, nonlinear finite element analysis was performed to investigate the behavioral characteristics of flexure-dominant RC members under cyclic load. The effects of axial force, arrangement of reinforcing bars, and reinforcement ratio on the cyclic behavior were studied. Based on the investigation, a simplified method to estimate the capacity of energy dissipation was proposed, and it was verified by the comparison with the finite element analyses and experiments. The proposed method can estimate the energy dissipation of RC members more precisely than currently used empirical equations, and it is easily applicable in practice.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.109-116
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• 2014

The flexural behavior test of UHPC segmental box girder which has 160 MPa compressive strength and 15.4 m length was carried out. The effect of steel fibers in combination with reinforcing bars on improving the ductile performance of UHPC box girder was evaluated by comparing the flexural behavior of the UHPC segmental box girders made by the two kinds of mixing portion. The test variables are volume fraction of steel fibers and the arrangement of reinforcing bars. The behavior of UHPC box girder BF2 composed of 1% volume fraction of steel fibers and longitudinal reinforcing bars in web and upper flange with stirrup showed the similar ductile behavior with the girder BF1 composed of 2% volume fraction without stirrup in elastic stress region. But BF1 had the better stiffness and showed the more ductile behavior in inelastic stress region. Segmental interfaces of UHPC box girder have not any crack and slide until the final flexural collapse load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.29-38
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• 1994

Linear composite theory as well as a finite element program is developed for axisymmetric elastomeric bearings. This study is limited to axisymmetrically loaded horizontal layered systems with linear, elastic, small' deformation conditions. A multiscale method is used in the development of the composite theory which enables us to model inhomogeneous layered composites as equivalent homogeneous, orthotropic material. Only continuity of the prime variables is required for the finite element analysis, allowing the use of simple $C_o$ elements whereas rather complicated theories presented in the past need more requirements. Four node isoparametric elements are used in the study. The developed theory of this paper is limited to linear conditions, however, the analysis can be extended to nonlinear behavior of flexible material in elastomeric bearing by using multiscale method presented here. Two numerical examples are examined and compared to the results of discrete and previously obtained composite analysis to verify the theory.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.93-101
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• 1989

A geometrically nonlinear cable finite element is presented to use in the static or dynamic modeling of offshore and onshore structures such as guyed tower, tension leg platform or mooring buoy, submarine cable, cable-stayed bridge, suspension bridge, cable roof and so on. The cable finite element is derived directly from the compatibility equations and flexibility matrix of elastic catenary cable theory for the arbitary plane loading and geome try. A general and virsatile computer program has been developed to perform the analyses of cable member itself or cable guyed or suspened structures, in which Newmark-$\beta$ method is used to obtain a time domain solution and Newton-Raphson iteration method is used to solve the nonlinear system of compatibility equations of cable and algebraic static or dynamic equations at each time step. The results from the static and dynamic analysis of a cable member by the computer program are summarized and presented.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.433-442
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• 2003

This paper presents a hypoplastic model for three-dimensional analysis of concrete structures under monotonic, cyclic, proportional and non-proportional loading. The constitutive model is based on the concept of equivalent uniaxial strains that allows the assumed orthotropic model to be described via three equivalent uniaxial stress-strain curves. The characteristics of these curves are obtained from the ultimate strength surface in the principal stress space based on the Willam-Warnke curve. A cap model is added to consider loading along or near the hydrostatic axis. The equivalent uniaxial curve is based on the Popovics and Saenz models. The post-peak behavior is adjusted to account for the effects of confinement and to describe the change in response from brittle to ductile as the lateral confinement increases. Correlation studies with available experimental tests are presented to demonstrate the model performance. Tests with monotonic loading on specimens under constant lateral confinement are considered first, followed by biaxial and triaxial tests with cyclic loads. The triaxial test example considers non-proportional loading.

• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.34-42
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• 2023

Considering the contribution of industrial facilities to the national economy, securing operability against earthquakes is very important. However, the basic concept of current seismic design mainly allows ductile behavior of facilities against large-scale earthquakes and only considers structural safety for the purpose of preventing collapse. In order to secure the operability of industrial facilities, the level of seismic performance to maintain operability may vary depending on the structural behavior characteristics of the industrial facility, and a seismic design method is needed to satisfy this. In this study, a ground storage tanks Nonlinear seismic behavior characteristics(R-μ-T) were analyzed through nonlinear response history analysis, and based on this, a new reliability-based, performance-based seismic design method was proposed.