• Proceedings of the KSME Conference
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• 2001.06b
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• pp.404-409
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• 2001

Seismic qualification of the Air Cleaning Units for nuclear power plant Ulchin 5&6 has been performed with the guideline of ASME Section III and IEEE 344 code. By using the structural and geometrical similarity analysis, the three models to be analyzed is condensed into a single model and, at the same time, the excitation forces and other operating loads for each model are encompassed with respect to different loading conditions. As the fundamental frequencies of the structure are found to be less than 33Hz, which is the upper frequency limit of the seismic load, response spectrum analysis using ANSYS is performed in order to combine the modal stresses within the frequency limit. In order to confirm the structural and electric stability of the major components, modal analysis theory is adopted to derive the required response spectrum at the component locations. As the all combined stresses obtained from the above procedures are less than allowable stresses and no mechanical or electrical failures are found from the seismic testing, the authors confirm the safety of the nuclear equipments Air Cleaning Units studied in this paper.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.513-520
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• 2002

This study is for seismic analysis of building structures with ambiguous modal direction This case is revealed symmetrical building structure or the structure that isn't coincided building axis with physical axis. Seismic analysis-time history analysis, response spectrum analysis and lateral force procedure-is carried out. It is concluded that analysis method for the structure with ambiguous modal direction don't suitable for lateral force procedure. It is recommended to use the CQC method for combining modal responses to the individual components and the SRSS rule for combining responses to the two horizontal components are of nearly equal intensities.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.455-473
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• 2016

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (${\eta}$). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.805-811
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• 2016

Prior to installation in a navy ship, shipboard equipment should be qualified by shock test requirements. The multi-function console mounted on the elastic platform of the ship should also withstand given shock loads. In this study, both real shock test methods, as well as numerical computer simulations using the finite element method were used to verify structural durability under shock load conditions. First, we used domestic test facilities to perform possible shock tests, including an impact hammer test, a drop table test and a shaker shock test. Full model tests satisfying the shock response spectrum level were performed. Thereafter, an analytical model of the complex console structure was built by the finite element method. Finally, numerical results were verified by modal test results of the real product and an FEA analysis was also performed with a full model transient response analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.4
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• pp.308-312
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• 2002

To determine the natural frequencies and damping ratios of composite laminated plates, we present an officient modal parameter estimation technique by developing residual spectrum based structural system reconstruction. The modal parameters can be estimated from poles and residues of the system transfer functions, derived from the state space system matrices. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios can be estimated using the modal coordinates of the structural dynamic system reconstructed from the experimental frequency response functions. These results are compared with those of finite element analysis and single-degree-of-freedom curve fitting.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.631-638
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• 2006

This paper considers the nonlinear direct spectrum method to estimate seismic performance of mixed building structures without iterative computations, given dynamic property $T_1$ from stiffness skeleton curve and nonlinear pseudo acceleration $A_{1y}$ and/or ductility ratio $\mu$ from response spectrum. Nonlinear response history analysis has been performed and analysed with various earthquakes for evaluation of correctness and confidence of nonlinear direct spectrum method.

• Earthquakes and Structures
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• v.20 no.4
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• pp.405-415
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• 2021

Following the dynamic property analysis and elaboration, linear response spectrum analysis (RSA) and response history analysis (RHA) were conducted on a representative hyperbolic cooling towers (HCT) in present study. The seismic responses in tower shell were illustrated in detail, including the internal force amplitude, modal contribution, influence from damping ratio, comparison of results got from RSA and RHA and especially the latitude distributions of internal forces. The results show that the eigenmodes could be classified in a new method into four types according to their mode shapes and only the lateral bending modes and vertical stretching modes are meaningful for horizontal and vertical earthquake correspondingly. The bending modes and seismic deformation display the same feature which is global lateral bending accompanied by minute circular flow displacement of section. This feature also decides the latitude distributions of internal forces as sine or cosine. Moreover, the following method is also proposed for approximate estimation of internal force amplitudes without time-consuming response history analysis: getting the response spectrums of the selected ground accelerations and then comparing values of response spectrums at the natural period of first lateral bending mode because it is always prime dominant for horizontal seismic responses.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.75-84
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• 2010

An in-cabinet response spectrum should be generated to perform the seismic qualification of devices and instruments mounted inside safety-related electrical equipment installed in nuclear power plants. The response spectrum is available by obtaining accurate seismic responses at the device mounting location of the cabinet. The dynamic behavior of most of electrical equipment may not be easily analyzed due to their complex mass and stiffness distributions. Considering these facts, this study proposes a procedure to estimate the seismic responses of a structure by a combination of a test and subsequent analysis. This technique firstly constructs the modal equations of the structure by using the experiment modal parameters obtained from the impact test. Then the seismic responses of the structure may be calculated by a mode superposition method. A simple steel frame structure was fabricated as a specimen for the validation of the proposed method. The seismic responses of the specimen were estimated by using the proposed technique and compared with the measurements obtained from the shaking table tests. The study results show that it is possible to accurately estimate the seismic response of the structure by using the experimental modal parameters obtained from the impact test.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.3
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• pp.181-186
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• 2002

A seismic analysis is one of crucial design procedures of an axial blower used in nuclear power Plants. The blower should be operated even in ar emergency such as an earthquake. The blower should be designed in order to stand against an earthquake. For the seismic analysis, Ive perform the modal analysis and then evaluate the required response spectrum (PRS) from the given floor response spectrum (FRS). A finite element model of the blower is established by using a commercial FEM code of ANSYS. After the finite element modeling. the natural frequencies. the mode shapes and the participation factors are obtained from the modal analysis. The PRS is acquired by a numerical approach on the basis of the principle of mode superposition. We verify the structura safety of the axial blower and confirm the validity of the present seismic analysis results.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.15-22
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• 2002

In the course of seismic probabilistic risk assessment(SPRA), seismic fragility analysis(SFA) is utilized as a tool to evaluate the actual seismic capacity of structures. This paper introduces a methodology of SFA and its evaluation procedures, especially focusing on the basic fragility variables. A new definition of the response spectrum shape factor as one of the most critical basic variables is suggested. The new factor is expressed as a term of linear algebraic sum using the modal contribution factor. The efficiency of new response spectrum shape factor is evaluated and validated to use in practice through the case study of the nuclear power plant structures. The case study results show that the proposed method can be effectively applicable to multi-mode structures with composite modal damping.