• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.27-33
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• 2004

Dynamic response analysis is conducted for a floating bridge subjected to multiple support earthquake excitation. The floating bridge used in this study is supported by discrete floating pontoons and horizontal pretension cables supported at both ends of the bridge. The bridge is modeled with finite elements and the hydrodynamic added mass and added damping due to the surrounding fluid around pontoons are obtained using boundary elements. During the analysis the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients. Multiple support excitation is introduced at both ends of the bridge and the time history response is compared to that of a simultaneous excitation. The results show that the multiple support excitation yields larger values in some responses. for example in cable tensions. than the sumultaneous excitation.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.99-109
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• 2000

Elastic dynamic responses analysis program for ship hulls considering slamming impact loads due to the voyage in large amplitude waves is developed. Ship hull structures are modeled by a thin-walled beam model in order to consider effects of shear deformation. The momentum slamming theory is used to derive nonlinear hydrodynamic forces considering intersection between wave particles and ship section. For the validation of the developed computer program, motions of a V-shaped simple section model and S-175 standard container model are calculated and analyzed. In each numerical example, time histories of relative displacement, velocity and vertical bending moment of a ship section are derived, considering the effect of slamming impacts in various wave conditions.ures near the free surface as well as the wake of the hydrofoil.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.281-290
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• 2007

In this paper, the dynamic behavior of a 12m plate girder railway bridge is analyzed using the commercial FEM program. A time history load is applied to a standard train load via the shape function ofthe beam element. In addition, lateral behavior characteristics were simulated using the Klingel sine movement. A feasibility study of the FEM program and an analysis were performed by comparing the displacement and the acceleration, from the experimental data and the results of the FEM analysis. the time history of the lateral and vertical displacements are reflected in the experimental results. Six kinds of reinforcements were studied from the effects of the displacement and the acceleration. The RF-1 model that was applied to the upper lateral bracing system, and the RF-3 model that reinforced the plate, turned out to be the most effective reinforcement methods with respect to weight limits and construction simplification.

• Journal of KSNVE
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• v.7 no.5
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• pp.837-845
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• 1997

The dynamic interactions between the reactor vessel and the control element drive mechanisms (CEDMs) of a pressurized water reactor are studied with the simplified mathematical model. The CEDMs are modeled as multiple substructures having different masses and the reactor vessel as a single degree of freedom system. The explicit equation for the frequency responses of the multiple substructure system are presented for the case of harmonic base excitations. The optimum dynamic characteristics of the CEDMs are presented to reduce the dynamic responses of the reactor vessel. The mathematical model and its response equations are verified by finite element analysis for the detailed model of the reactor vessel and the CEDMs for the harmonic base excitations. It is finally shown that the optimal dynamic characteristics of the CEDM presented can be applicable for the aseismic design.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.61-71
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• 1998

This paper describes a dynamic fracture behaviors of structural elements under elastic or elasto-plastic stress waves in two dimensional space. The governing equation of this problem has the type of hyperbolic partial differential equation, which consists of the equation of motions and incremental elasto-plastic constitutive equations. To solve this problem we introduce Zwas' method which is based on the finite difference method. Additionally, in order to deal with the dynamic behavior of elasto-plastic problems, an elasto-plastic loading path in the stress space is proposed to model the plastic yield phenomenon. Based on the result of this computation, the dynamic stress intensity factor at the crack tip of an elastic material is calculated, and the time history of a plastic zone of a elasto-plastic material is to be shown.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.9-16
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• 2024

Using the proper orthogonal decomposition (POD) based intrusive reduced order model (ROM), the total degrees of freedom of the structural system can be significantly reduced and the critical time step satisfying the conditional stability increases in the explicit time integrations. In this study, therefore, the changes in the critical time step in the explicit time integrations are investigated using both the POD-ROM and Voronoi-cell lattice model (VCLM). The snapshot matrix is composed of the data from the structural response under the arbitrary dynamic loads such as seismic excitation, from which the POD-ROM is constructed and the predictive capability is validated. The simulated results show that the significant reduction in the computational time can be achieved using the POD-ROM with sufficiently ensuring the numerical accuracy in the seismic analyses. In addition, the validations show that the POD based intrusive ROM is compatible with the Voronoi-cell lattice based explicit dynamic analyses. In the future study, the research results will be utilized as an elemental technology for the developments of the real-time predictive models or monitoring system involving the high-fidelity simulations of structural dynamics.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.1-10
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• 1998

In the dynamic soil-structure interaction(SSI) analysis, numerous uncertain parameters are involved. They include the uncertainties in the definition of input motions, modeling of soil-structure interaction systems. analysis techniques, etc. This paper presents the results of parametric studies of the seismic responses of a reactor containment structure built on the viscoelastic layered soil. Among the numerous parameter, this study concentrates on the effects of definition point of the input motion, embedment of structure to the base soil, thickness of the top soil layer, and rigidity of the base soil. The substructure method using frequency independent impedances is adopted. The method is based on the mode superposition method in time domain using the composite modal damping values of th SSI system computed from the ratio of dissipated energy to the strain energy for each model. From the study results, the sensitivity of each parameter on the earthquake responses has been suggested for the practical application of the substructure method of SSI analysis.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.352-359
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• 2003

철도나 고속철도 교량에 사용되는 장대레일은 차량에 의한 동적충격의 완화, 주행시 승차감의 향상과 같은 장점을 가져온 반면에, 인접한 교량의 연결부에서 레일과 교량 상부구조간의 거동 불일치로 인해 레일에 부가적인 응력을 발생시킨다. 이러한 부가적인 레일응력과 지반운동의 특성에 따른 구조적 응답의 민감도 및 열차의 안전한 정지를 고려하여, 지진 발생시 고속철도교량의 장대레일 응력을 해석하기 위해 레일의 재료비선형성, 지반운동의 위상차 등을 고려한 비선형 시간이력해석 방법을 제시하였다. 그리고 우리나라의 여러 지반조건을 고려하고 고속철도의 대표적인 연속교량 모델에 적용하여 제시한 방법의 타당성을 검토하였다.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.10
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• pp.127-133
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• 2019

Damage to high-rise buildings caused by earthquakes is less frequency due to small distribution of high-rise buildings and low transmissibility of seismic motion to high-rise buildings. However, demand for high-rise buildings is increasing for development of construction technology and efficient land use. In addition, if high-rise buildings are constructed on soft ground such as landfill, transmissibility of seismic motion due to long-periodization of seismic waves is likely to increase. Thus, with development of technology, buildings are required to expand range of seismic design such as safety for long-period seismic waves. Therefore, in this study, dynamic experiments were performed to evaluate response characteristics of high-rise buildings according to period characteristics of seismicwaves and time history analysis was performed to verify them.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.51-62
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• 2016

Parametric studies for various site conditions by using 3d numerical model were carried out in order to estimate dynamic behavior of soil-pile-structure system in dry soil deposits. Proposed model was analyzed in time domain using FLAC3D which is commercial finite difference code to properly simulate nonlinear response of soil under strong earthquake. Mohr-Coulomb criterion was adopted as soil constitutive model. Soil nonlinearity was considered by adopting the hysteretic damping model, and an interface model which can simulate separation and slip between soil and pile was adopted. Simplified continuum modeling was used as boundary condition to reduce analysis time. Also, initial shear modulus and yield depth were appropriately determined for accurate simulation of system's nonlinear behavior. Parametric study was performed by varying weight of superstructure, pile length, pile head fixity, soil relative density with proposed numerical model. From the results of parametric study, it is identified that inertial force induced by superstructure is dominant on dynamic behavior of soil-pile-structure system and effect of kinematic force induced by soil movement was relatively small. Difference in dynamic behavior according to the pile length and pile head fixity was also numerically investigated.