• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2819-2830
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• 2009

Load bearing structural members in a wide variety of applications accumulate damage over their service life. During experiment much effort and cost is needed for measuring structural safety assessment. The sparseness and errors of measured data have to be considered during the safety estimation of structures. This paper introduces parameter estimation and damage identification algorithm by a system identification using static and dynamic response. The equation error estimator and response error widely used in system identification are based on the minimization of least squared error between measured and calculated responses by a mathematical model of a structure. Since each estimator has a specific form of application in noisy environment and proposes different definitions for these forms. To study the behaviour of the estimators in noisy environment Using Monte Carlo simulation, and a data measured pertubation scheme is adopted to investigate the influence of measurement errors on identification results. The assessment result by static and dynamic response were compared, and the efficiency and applicabilities of the proposed algorithm are demonstrated through simulated static and dynamic responses of a dimensional truss type structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.65-73
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• 2002

It has been recognized that the damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear time history analyses, monotonic static nonlinear analyses, or equivalent static analyses with simulated nonlinear influences. Some building codes propose the capacity spectrum method based on the nonlinear static analysis(pushover analysis) to determine the earthquake-induced demand given by the structure pushover curve. These procedures are conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) systems. The purpose of this paper is to investigate the accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters. The conclusions of this study are as follows; 1) NDSM is considered as practical method because the peak deformations of nonlinear system of MDF by NDSM are almost equal to the results of nonlinear time history analysis(NTHA) for various ground motions. 2) When the results of NDSM are compared with those of NTHA. mean of errors is the smallest in case of post-yielding stiffness factor 0.1, static force by MAD(modal adaptive distribution) and unloading stiffness degradation factor 0.2~0.3.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.349-359
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• 2016

In order to analytically evaluate buffeting responses, the analysis of wind characteristics such as turbulence intensity, turbulence length, gust, roughness coefficient, etc must be a priority. Static aerodynamic force coefficients, flutter coefficients, structural damping ratios, aerodynamic damping ratios and natural frequencies affect the analytical responses. The bridge interested in this paper has being been used for 32 years. As the time passes, current terrain conditions around the bridge are different markedly from the conditions it was built 32 years ago. Also, wind environments were considerably varied by the climate change. For this reason, it is necessary to evaluate the turbulence intensity, length, spectrum and roughness coefficient of the bridge site from full-scale measurements using the structural health monitoring system. The evaluation results indicate that wind characteristics of bridge site is analogous to that of open terrain although the bridge is located on the coastal area. To calculate buffeting responses, the analysis variables such as damping ratios, static aerodynamic force coefficients and natural frequency were evaluated from measured data. The analysis was performed with regard to 4 cases. The evaluated variables from measured data are applied to the first and second analysis cases. And the other analysis cases were performed based on Design Guidelines for Steel Cable Supported Bridges. The calculated responses of each analysis cases are compared with the buffeting response measured at less than 25m/s wind speed. It is verified that the responses by the numerical analysis applying the estimated variables based on full-scale measurements are well agreed with the measured actual buffeting responses under wind speed 25m/s. Also, the extreme wind speed corresponding to a recurrence interval 200 years is derived from Gumbel distribution. The derived wind speed for return period of 200 years is 45m/s. Therefore the buffeting responses at wind speed 45m/s is determined by the analysis applying the estimated variables.

• Survey Research
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• v.12 no.2
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• pp.51-76
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• 2011

Analyzing the 2009 Korean General Social Survey(KGSS), this study attempts to elucidate the mechanism how content-irrelevant response patterns are formed in the social survey. This study investigates the relationship between personality traits and response styles. Specifically, the effects of Big Five factors(extraversion, agreeableness, conscientiousness, emotional stability, openness to experience) of personality on the acquiescent response styles(ARS) and extreme response styles(ERS) are examined, controlling for individual characteristics and interview contexts. The results show that ERS is positively affected by extraversion, openness to experience, agreeableness, and conscientiousness, whereas ARS is not significantly associated with any dimension of personality traits. The implications of findings and the methods to reduce response bias are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5A
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• pp.341-349
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• 2011

The main purpose of this study is to investigate the affect of various turbulence properties on aerodynamic characteristics of twin box bridge section. To achieve this goal, active turbulence generator which successfully simulated various target turbulences was developed in the wind tunnel. From the wind tunnel tests, turbulence integral length scale did not affect on the aerodynamic forces and flutter derivatives except for the $A_1^*$ curve. Turbulence intensity gave slight effect on the unsteady aerodynamic force, but turbulence integral length scale did not affect the self-excited forces except vertical direction component.

• Proceedings of the Safety Management and Science Conference
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• 2011.11a
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• pp.75-84
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• 2011

In this paper various numerical analyses are carried out according to behavior characteristics of structures and types of seismic design methods as a study on the seismic analysis for underground structures. Equivalent Static Force Procedure and Response Displacement Method commonly used in practiral design are adopted and Time History Method regarded as the most accurate analysis method is selected to verify the results of two practical methods above. 3-D modelling for seismic analysis of structures is introduced to consider Structure Soil Interaction and all analyses are based on Korea Structural Concrete Design Code. After numerical analyses, Equivalent Static Force Procedure and Response Displacement Method showed relatively lager values than those of Time History Method, so it is identified that above two methods are suitable for practical design purpose.

• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.61-70
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• 2011

The impact protection system consists of an arrangement of circular sheet pile cofferdams-denoted dolphin structuredeeply embedded in the seabed, filled with crushed rock and closed at the top with a robust concrete cap. Centrifuge model tests were performed to investigation the behaviors of dolphins in this study. Total 7 quasi-model tests and 11 dynamic model tests were performed. The main experimental results can be summarized as follows. Firstly, The experimental force-displacement results for quasi-static tests show a limited influence on the initial stiffness of the structure from the change in fill density and the related change in the stiffness of the fill. And by comparing the dissipation at the same dolphin displacement it was found that the denser fill increase the dissipation by 16% for the 20m dolphin and by 23% for the 30m dolphin. The larger sensitivity for the large dolphin is explained by a larger contribution to the dissipation from strain in the fill. In low level impacts the dynamic force-response is up to 26~58% larger than the quasi-static and the dissipation response is showed larger in small displacement. Hence, it is concluded conservative to use the quasi-static response characteristics in the approximation of the response, and it is further concluded that the dolphin resistance to low level impacts is demonstrated to be equivalent and even superior to the high level impacts.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1487-1494
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• 1990

In this paper the dynamic characteristics of self acting air lubricated slider bearing of hard disk/head system are investigated. The dynamic equations of magnetic head mechanism considering both parallel and pitch motion and the time dependent modified Reynolds equation are analyzed and the dynamic pressure distribution of air film is numerically calculated in frequency domain by small perturbation method and finite difference scheme with variable grid. The dynamic response of the slider spacing is obtained accordingly as the moving recording surface vibrates in parallel mode.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.195-204
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• 2004

To evaluate inelastic seismic responses of multi-span bridge structures, the capacity spectrum method(CSM) incorporating the equivalent single-degree-of freedom(ESDOF) method is presented. Application of the CSM incorporating the ESDOF method is illustrated by example analysis for symmetric and asymmetric bridge structures. To investigate an accuracy of the CSM, the maximum displacements estimated by the CSM are compared to those by inelastic time history analysis for several artificial earthquakes. The results show that the CSM provided conservative estimates of the maximum displacements for the symmetric and asymmetric bridge structures, and the trend of conservative estimates of the asymmetric bridge structures was significantly larger than that of the symmetric bridge structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.84-87
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• 2011

본 연구에서는 버페팅 해석을 통해 현수교 캣워크에 작용하는 풍하중에 대한 정적 및 동적 응답을 알아 보고 진동 억제 대책을 제시하였다. 캣워크는 영구구조물이 아닌 임시구조물이기 때문에 그동안 절적한 평가가 수행되지 못하였다. 따라서 본 연구는 풍하중에 의한 캣워크의 동적 응답을 해석적인 방법을 통해 알아보았으며, 동적 변위를 산정하기 위해 시간이력 해석 방법을 통해 버페팅 해석을 수행하였다. 그 결과로 부터 캣워크의 수평변위를 억제하기 위해 주케이블을 시공중에 연결하는 방법과 스테이 로프를 설치하는 방법을 제시하였다.