• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.183-192
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• 2004

New dynamic analysis procedures lot the vertically drilled sea water pile are suggested and demonstrated by the typical design Problem. Pile structure submerged in the sea water as well as forces by the ocean waves and tidal currents are modeled and formulated by finite element method. To obtain wave forces for the finite element equation, Airy's wave theory is tested and selected among others. Lateral lifting forces induced by the vortex shedding of current flow is simply based on the harmonic function with the Strouhal frequency and lifting coefficient. Natural frequencies and frequency responses for the pile are calculated by NASTRAN using the results of the formulation. Dynamic displacement and stress results obtained by these procedures are shown to be applicable to predict the dynamic behaviors of the ocean pile by the wave and lifting forces as a preliminary design analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.71-80
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• 2013

According to design specifications for structural safety, a bridge in initial design step has been modelled to have larger self-weight, external loads and less stiffness than those of real one in service. Thereby measured buffeting responses of existing bridge show different distributions from those of the design model in design step. In order to obtain accurate buffeting responses of the in-site bridge, the analysis model needs to be modified by considering the measured natural frequencies. Until now, a Manual Tuning Method (MTM) has been widely used to obtain the Measurement-based Model(MBM) that has equal natural frequencies to the real bridge. However, since state variables can be selected randomly and its result is not apt to converge exact rapidly, MTM takes a lot of effort and elapsed time. This study presents Buffeting Response Correction Method (BRCM) to obtain more exact buffeting response above MTM. The BRCM is based on the idea the commonly used frequency domain buffeting analysis does not need all structural properties except mode shapes, natural frequencies and damping ratio. BRCM is used to improve each modal buffeting responses of the design model by substituting measured natural frequencies. The measured natural frequencies are determined from acceleration time-history in ordinary vibration of the real bridge. As illustrated examples, simple beam is applied to compare the results of BRCM with those of a assumed MBM by numerical simulation. Buffeting responses of BRCM are shown to be appropriate for those of in-site bridge and the difference is less than 3% between the responses of BRCM and MTM. Therefore, BRCM can calculate easily and conveniently the buffeting responses and improve effectively maintenance and management of in-site bridge than MTM.

• Journal of KIISE:Software and Applications
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• v.26 no.8
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• pp.1018-1027
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• 1999

속성 문법은 언어의 정적인 의미구조를 표현하는 형식적인 표기법으로 동적인 의미구조를 표현하기는 부적절하다. 동적 의미구조를 잘 명세하고 명세된 언어를 구현하기 위해서 기존의 속성 문법을 확장하여 언어 구현에 필요한 동적인 작용들(actions)을 잘 표현해야 한다. 본 논문에서는 속성 문법을 확장하여 정적이고 동적인 의미구조를 잘 표현할 수 있는 새로운 작용 식(action equation)을 제시한다. 제시된 작용 식(action equation)의 동적인 의미 구조로 부터 SIMP 언어의 점진 해석기(incremental interpreter)를 설계하고 구현한다. 점진 해석기는 언어 기반의 프로그래밍 환경에서 수정된 부분만을 번역하여 프로그램의 전체 실행 결과를 얻는 해석기를 의미한다. 본 해석기는 SUN 1000에서 Lex와 Yacc을 사용해서 C 언어로 설계하고 구현하였다. 예제 프로그램을 실행시켰을 때 배정 문이나 IF문의 경우는 매우 효율적이었고 Loop의 경우는 재실행될 필요가 있는 영향받는 명령문들이 적을수록 점진 해석이 더 효율적으로 수행된다.Abstract Attribute grammars are a formal notation which expresses the static semantics of programming languages, but they are not suitable for expressing dynamic semantics. To describe dynamic semantics and implement a specified language, we extend attribute grammars and present new action equations which describe static and dynamic semantics. The incremental interpreter of a SIMP language is designed and implemented from the dynamic semantics of presented action equations. The incremental interpreter is to translate only modified part in the language-based programming environments and have results of whole program.Our interpreter is implemented in C with Lex and Yacc on SUN 1000. When we execute example programs, the incremental evaluation of any assignment and IF statements executes efficiently. But in the case of loop, we execute efficiently when the effected statements to be reexecuted in the loop are of small number.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.55-64
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• 2001

Industrial machines are sometimes exposed to the danger of earthquake. In the design of a mechanical system, this factor should be accounted for from the viewpoint of reliability to analyze a complex nonlinear structure system under random excitation is proposed. First, the actual random excitation, such as earthquake, is approximated to the corresponding Gaussian process for the statistical analysis. The modal equations of overall system are expanded sequentially. Then, the perturbed equations are synthesized into the overall system and solved in probabilistic way. Several statistical properties of a random process that are of interest in random vibration are evaluated in each substructure. Comparing with the results of the numerical simulation proved the efficiency of the proposed method.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.51-58
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• 2005

Many RC building structures of multiple uses constructed in Korea have the Irregularities of torsion and soft story at bottom stories simultaneously. Seismic design codes generally require dynamic analysis and to take into account the effect or earthquake excitations in the orthogonal direction using the approximate methods of 100/30 and SRSS for type of building structures. And ail buildings should be designed to be safe in any direction of earthquake input. But, most of designers have difficulty in considering the orthogonal and directional effect of earthquake. The objective of the study stated herein is to verily 1) the effect of the choice of the reference axes on the seismic design member forces by comparing the analytical results on member forces using the principal axes suggested by Wilson and the global axes generally adopted in design office, 2) the validity or the 100/30 and SRSS methods by comparing the member forces obtained through linear elastic time history analysis with those obtained through using response spectrum analysis and 100/30 (or SRSS) methods. Based on the observations on the analytical results, it is concluded as follows; 1) The values of member forces by principal axes can be about $15\%$ smaller than those by the global axes in the example structure. 2) Though the values of member forces given by time history analysis are generally within the peak values predicted by 100/30 and SRSS methods, many member force vectors $(P,\;M_y,\;and\;M_z)$ by lime history analysis were located outside the boundaries predicted by the approximate method such as the 100/30 method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.5
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• pp.326-332
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• 2010

Critical response of seawater pump impeller shaft structure to various exciting loads is a fundamental factor in re-designing of the structure after its functional failure. In this paper, a typical case of the shaft structure's failure is investigated for re-designing purposes. Failure causes of interest are excessive bending moment, fatigue loads and dynamic resonance due to relevant motor rotation and unbalancing of the rotation loads. Static analyses of shaft structure under the conditions of concerned loads are carried out, followed by a dynamic investigation of the effects of resonance between the shaft and the motor on the structure. The relevant structural analyses are carried out using the Finite Element Methods combined with ANSYS code. Based on these, the primary cause for the shaft's structural failure is obtained. It is found that the change of the bending stiffness of the shaft is the primary concern in the re-designing process. A guideline for the re-design process of the seawater pump shaft structure is established, and a re-design scheme of the structure is proposed.

• Journal of the Korean Geotechnical Society
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• v.34 no.8
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• pp.15-26
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• 2018

Recently, as the seismic performance based design methods have been introduced, dynamic numerical analyses need to be performed to evaluate the actual performance of structures under earthquakes. The verification of the numerical modeling is the most important for the performance based design. Therefore, 2-dimensional numerical analyses were performed to simulate the seismic behavior of a pile-supported structure, to provide the proper numerical modeling and to determine of input parameters. A dynamic centrifuge test of a pile group in dry loose sand was simulated to verify the applicability of the numerical model. The numerical modeling was carefully made to reflect the actual condition of the centrifuge test including dynamic soil properties, soil-pile interaction, boundary condition, the modeling of the group pile and structure and so on. The predicted behavior of the numerical analyses successfully simulated the acceleration variation in ground, the moment and displacement of the pile, and the displacement and acceleration of the structure. Therefore, the adopted numerical modeling and the input parameters can be used to evaluate the seismic performance of pile groups.

• Computational Structural Engineering
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• v.3 no.4
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• pp.123-132
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• 1990

In current practice of earthquake resistant design the equivalent lateral force procedure is widely used because of its simplicity and convenience. But the equivalent lateral force procedure is derived based on the assumptions that the dynamic behavior of the structure is governed primarily by the fundamental vibration mode and the effect of higher modes is included in an approximate manner. Therefore the prediction of dynamic responses of structures using the equivalent lateral force procedure is not reliable when the effect of higher vibration modes on the dynamic behavior is significant. In this study, design seismic load which can reflect the effect of higher vibration modes is proposed from the point of view of proper assessment of story shears which have the major influence on the design moment of beams and columns. To evaluate the effect of higher modes, differences between the story force based on the equivalent lateral force procedure specified in current earthquake resistance building code and the one based on modal analysis using design spectrum analysis are examined. From these results an improved design seismic load for the equivalent lateral force procedure which can reflect the effect of higher vibration modes are proposed.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.83-93
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• 2004

In this study. the Modified Response Displacement Method(MRDM) for seismic design of underground box-type structures is proposed. Firstly, to investigate the applicability of the conventional RDM, various parametric studies are performed according to buried depth and soil conditions. Results from the conventional RDM are compared with those of time history analysis in terms of the maximum bending moment and relative displacement. The comparison shows that the velocity response spectrum and the determination method of foundation modulus which significantly influence the accuracy of RDM should be modified. Thus, the modified velocity response spectrum and the new determination method of foundation modulus are proposed under consideration of domestic conditions. In order to demonstrate the accuracy and validity of the proposed MRDM numerical analyses are performed according to different parameters such as depth of base rock, height and width of box, buried depth and soil condition. the comparison with the results of the time history analysis verifies the feasibility of the proposed MRDM for the seismic analysis.

• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.523-535
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• 2014

According to the capacity design concept underlying current steel seimsic provisions, the braces in concentrically braced frames should dissipate seismic energy through cyclic tension yielding and compression buckling. On the other hand, the beams and the columns in the braced bay should remain elastic for gravity load actions and additional column axial forces resulting from the brace buckling and yielding. However, due to the difficulty in accumulating the yielding and buckling-induced column forces from different stories, empirical and often conservative approaches have been used in design practice. Recently a totally different approach was proposed by Cho, Lee, and Kim (2011) for the prediction of column axial forces in inverted V-braced frames by explicitly considering brace buckling. The idea proposed in their study is extended to X-braced seismic frames which have structural member configurations and load transfer mechanism different from those of inverted V-braced frames. Especially, a more efficient rule is proposed in combining multi-mode effects on the column axial forces by using the modal-mass based weighting factor. The four methods proposed in this study are evaluated based on extensive inelastic dynamic analysis results.