확장형 칼만필터를 이용한 현수교의 감쇠성능 평가

박동욱(Park Dong-Uk),김남식(Kim Nam-Sik) 대한토목학회 2011 대한토목학회논문집 A Vol.31 No.2A

감쇠비는 현수교에 있어서 교량진동을 평가하기 위한 중요한 동적 요소 중 하나이다. 하지만, 실재 현수교에서 계측된 상시 진동신호로부터 감쇠비를 직접적으로 추정하는 것은 현실적으로 매우 어려운 일이다. 뿐만 아니라, 한정된 계측자료를 이용하여 추정된 감쇠비로부터 공기역학적 감쇠와 마찰 감쇠를 구분하는 것은 더욱 어렵다. Macdonald는 2005년 발표한 자료에서 공기 역학적 감쇠성능은 풍속에 따라 선형적으로 증가한다고 하였으며, Park등은 감쇠성능은 진동의 크기에 따라 변화할 수 있다고 하였다. 따라서 본 논문에서는 이러한 감쇠비, 풍속, 진동의 크기 사이의 관계를 연구하여, 추정 감쇠비로부터 공기역학적 감쇠와 마찰 감쇠를 구분하고자 하였다. 본 논문에서 감쇠비 추정대상으로는 전라남도 고흥에 위치한 소록대교를 선택하였으며, 감쇠비 추정에는 Hilbert 변환법을 이용한 방법과 확장형 칼만필터를 이용하였다. 또한 두 방법으로 추정된 감쇠비들을 상호 비교를 실시하였다. 그 결과, 상시진동 자료와 차량재하실험으로부터 얻어진 자료를 이용하여 추정된 감쇠비와 풍속, 그리고 가속도의 크기를 이용하여 추정 감쇠비로부터 공기역학적 감쇠 성능과 마찰 감쇠 성능의 구분이 가능하다는 것을 알 수 있었다. The damping ratio as an index of bridge vibration could be considered as one of the important dynamic characteristics of a suspension bridge. But estimating of damping ratio on an existing suspension bridge under ambient vibration condition could be a laborious task. Moreover, it is not simple to directly distinguish aerodynamic damping and friction damping from apparent damping. According to previous studies, the aerodynamic damping properties can be linearly affected by wind speed level, and apparent damping ratio can be affected by amplitude of vibration. Therefore, in this article, the relationships among damping ratio, wind speed level and amplitude of acceleration were studied for separating extract aerodynamic damping and friction damping from apparent damping. Damping ratios on Sorok Bridge, a suspension bridge which is a located in Go-Heung, Korea, were estimated by two different methods as using Hilbert transform and extended Kalman filter which were well known as effective estimation methods for non-linear state. It was possible to distinguish aerodynamic damping and friction damping from apparent damping using averaged normal components of wind speed, RMQ values of acceleration, and estimated damping ratios from wind-induced vibration responses and vehicle loading responses.

Wind-induced conductor response considering the nonproportionality of generalized aerodynamic damping

Wenjuan Lou,Dengguo Wu,Haiwei Xu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7

Aerodynamic damping is a key factor that influences the wind-induced responses of transmission conductors. The inaccurate estimation of aerodynamic damping leads to misunderstanding of conductor response to wind actions. For dynamic response analysis in the frequency domain, the generalized aerodynamic damping matrix used to solve conductor motion is diagonal. This study reanalyzed the conductor generalized aerodynamic damping matrix by considering its horizontal and vertical motions and the coupling effects of different modes. The derived generalized aerodynamic damping was a nondiagonal matrix, and we defined it as nonproportional generalized aerodynamic damping. Variations in the aerodynamic damping ratio and the nonproportionality of generalized aerodynamic damping with wind speed were investigated through numerical studies of single- and triple-span conductors. Triple-span conductors with different span lengths, hanging heights, and initial pretension forces were adopted to discuss the effects of the nonproportionality of generalized aerodynamic damping on estimating the dynamic responses of conductors. Results showed that neglecting the vertical motion of a conductor leads to an overestimation of the aerodynamic damping ratio, especially under high wind speed conditions. The nonproportionality of generalized aerodynamic damping is highest when the incoming wind speed at 10 m is 25 m/s. Ignoring such nonproportionality leads to an overestimation of the resonant responses of conductors but exerts minimal effects on total fluctuating responses mainly contributed by background components. Therefore, for a transmission conductor with a significant resonant response, the nonproportionality effect of generalized aerodynamic damping must be considered. Increasing span length and conductor height or reducing initial pretension force seems to enhance nonproportionality effects on conductor responses.

Structural Damping Effects on Stability of a Cantilever Column under Sub-tangentially Follower Force

Dong-Ju Min(민동주),Jae-gyun Park(박재균),Moon-Young Kim(김문영) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4

A stability theory of a damped cantilever column under sub-tangential follower forces is first summarized based on the stability map. It is then demonstrated that internal and external damping can be exactly transformed to Rayleigh damping so that the damping coefficients can be effectively determined using proportional damping. Particularly a parametric study with variation of damping coefficients is performed in association with flutter loads of Beck column and it is shown that two damping coefficients can be correctly estimated for real systems under the assumption of Rayleigh damping. Finally a frequency equation of a cantilever beam subjected to both a sub-tangentially follower force and two kinds of damping forces is presented in the closed-form and its stability maps are constructed and compared with FE solutions in the practical range of damping coefficients.

ON ANALYTICAL SOLUTION OF NON LINEAR ROLL EQUATION OF SHlPS

S. Rao TATA,Kuniaki SHOJI,Shigeo MITA,Kiyokazu MINAMI 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2006 No.-

Out of all types of motions the critical motions leading to capsize is roll. The dynamic amplification in case of roll motion may be large for ships as roll natural frequency generally falls within the frequency range of wave energy spectrum typical used for estimation of motion spectrum. Roll motion is highly non-linear in nature. There are various representations of non-linear damping and restoring available in literature. In this paper an uncoupled non-linear roll equations with three representation of damping and cubic restoring term is solved using a perturbation technique. Damping moment representations are linear plus quadratic velocity damping, angle dependant damping and linear plus cubic velocity dependant damping. Numerical value of linear damping coefficient is almost same for all types but non-linear damping is different. Linear and non-linear damping coefficients are obtained form free roll decay tests. External rolling moment is assumed as deterministic with sinusoidal form. Maximum roll amplitude of non-linear roll equation with various representations of damping is calculated using analytical procedure and compared with experimental results, which are obtained from forced tests in regular waves by varying frequency with three wave heights. Experiments indicate influence of non-linearity at resonance frequency. Both experiment and analytical results indicates increase in maximum roll amplitude with wave slope at resonance. Analytical results are composed with experiment results which indicate maximum roll amplitude analytically obtained with angle dependent and cubic velocity damping are equal and difference from experiments with these damping are less compared to non-linear equation with quadratic velocity damping.

한국형 중풍 변증 표준시안의 습담 변증 지표에 대한 연구

조현경,김중길,강병갑,유병찬,백경민,이인,최선미,설인찬,Jo, Hyun-Kyung,Kim, Joong-Kil,Kang, Byeong-Kab,Yu, Byeong-Chan,Baek, Kyung-Min,Lee, In,Choi, Sun-Mi,Seol, In-Chan 대한한방내과학회 2006 大韓韓方內科學會誌 Vol.27 No.1

Objectives : This study was done to investigate clinical frequency and correlation among the indicators of dampness-phlegm pattern identification settled by tentative Korean Standard Differentiation of the Symptoms and Signs for Stroke. Methods : The subjects were 147 hospitalized patients with stroke, and a list of registry was made for each of them. Among the five types of pattern identification, fire-heat, dampness-phlegm, blood-stasis and deficiency of Qi and of Yin, those that have shown a high frequency in dampness-phlegm type were categorized as the dampness-phlegm pattern group. Frequency of dampness-phlegm indicators was compared with those from the non-dampness-phlegm pattern group. Correlations among dampness-phlegm indicators were also studied. Results : 1. Dampness-phlegm pattern group included 26 patients out of 147. 2. Among the indicators of dampness-phlegm pattern. those, in order of highest frequency, were 'tiredness or sluggishness', 'white Coated tongue' and 'sputum'. 3. In comparing dampness-phlegm pattern group with non-dampness-phlegml group, the indicators such as 'lightheadedness', 'nigrescence', 'sputum', 'dermatic dysaesthesia' showed significantly high frequency. 4. Among the indicators, 'sputum' and 'tiredness or sluggishness', 'sputum' and 'yellow coated tongue', and 'white coated tongue' and 'yellow coated tongue' showed significant correlation. 5. In investigation of the correlation of scale in symptoms, various results such as positive correlation and negative correlation were obtained. Conclusion : In this study, more sensitive indicators of dampness-phlegm pattern identification were found. Based on these results, it is suggested that a more practical Korean Standard Differentiation of the Symptoms and Signs of Stroke would be established through continuous clinical studies by giving weight on each specific type of pattern identification.

Generalized complex mode superposition approach for non-classically damped systems

Huating Chen,Yanhui Liu,Ping Tan 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.3

Passive control technologies are commonly used in several areas to suppress structural vibrations by the addition of supplementary damping, and some modal damping may be heavy beyond critical damping even for regular structures with energy dissipation devices. The design of passive control structures is typically based on (complex) mode superposition approaches. However, the conventional mode superposition approach is predominantly applied to cases of under-critical damping. Moreover, when any modal damping ratio is equal or close to 1.0, the system becomes defective, i.e., a complete set of eigenvectors cannot be obtained such that some well-known algorithms for the quadratic eigenvalue problem are invalid. In this paper, a generalized complex mode superposition method that is suitable for under-critical, critical and over-critical damping is proposed and expressed in a unified form for structural displacement, velocity and acceleration responses. In the new method, the conventional algorithm for the eigenvalue problem is still valid, even though the system becomes defective due to critical modal damping. Based on the modal truncation error analysis, modal corrected methods for displacement and acceleration responses are developed to approximately consider the contribution of the truncated higher modes. Finally, the implementation of the proposed methods is presented through two numerical examples, and the effectiveness is investigated. The results also show that over-critically damped modes have a significant impact on structural responses. This study is a development of the original complex mode superposition method and can be applied well to dynamic analyses of non-classically damped systems.

Analytical and numerical algorithm for exploring dynamic response of non-classically damped hybrid structures

Raheem, Shehata E. Abdel Techno-Press 2014 Coupled systems mechanics Vol.3 No.2

The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of hybrid structure with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. A numerical algorithm capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to explore the dynamic response of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified model of 2 coupled lumped masses to investigate the effects of subsystems different damping, mass ratio, frequency ratio on dynamic characteristics and equivalent modal damping; the second approach employs a detailed numerical step-by step integration procedure.

Estimation of NonlinearSite Effects of Soil Profiles in Korea

이홍성,윤세웅,박두희,김인태 한국지반공학회 2008 한국지반공학회논문집 Vol.24 No.3

In a nonlinear site response analysis which is performed in time domain, small strain damping is modeled as viscous damping through use of various forms of Rayleigh damping formulations. Small strain damping of soil is known to be independent of the loading frequency, but the viscous damping is greatly influenced by the loading frequency. The type of Rayleigh damping formulation has a pronounced influence on the dependence. This paper performs a series of nonlinear analyses to evaluate the degree of influence of the viscous damping formulation on Korean soil profiles. Analyses highlight the strong influence of the viscous damping formulation for soil profiles exceeding 30 m in thickness, commonly used in simplified Rayleigh damping formulation overestimating energy dissipation at high frequencies due to artificially introduced damping. When using the full Rayleigh damping formulation and carefully selecting the optimum modes, the artificial damping is greatly reduced. Results are further compared to equivalent linear analyses. The equivalent linear analyses can overestimate the peak ground acceleration even for shallow profiles less than 20 m in thickness.

중풍 환자의 습담 설진과 고지혈증의 연관성에 관한 연구

강지선 ( Ji Sun Kang ),김동현 ( Dong Hyun Kim ),신현수 ( Hyun Soo Shin ),조창환 ( Chang Hwan Jo ),이재휘 ( Jae Hwi Lee ),강병갑 ( Byeong Gab Kang ),안정조 ( Joung Jo An ),조현경 ( Hyun Kyung Jo ),유호룡 ( Ho Rhyong Yoo ),설인찬 ( 대한한의진단학회 2009 大韓韓醫診斷學會誌 Vol.13 No.2

Objectives : This study was aimed to clarify the relationship between the tongue diagnosis of dampness-phlegm and hyperlipidemia in acute stroke patients. Methods : We analyzed the data of 1405 patients with acute stroke in 10 oriental medical hospitals from November 2006 to December 2008. We classified patients into two groups, dampness-phlegm and non dampness-phlegm by tongue diagnosis such as the white coating of the tongue, thick coating of the tongue, swollen tongue and teeth printed tongue which is oriental medical diagnosis. And We analyzed their characteristics with type of stroke and lipid blood level. Results : 1. There was no significant difference of stroke type between the dampness-phlegm tongue diagnosis group and the non dampness-phlegm tongue diagnosis group. 2. The ratio of SVO was higher in dampness-phlegm tongue diagnosis group (76.06%) than the non dampness-phlegm tongue diagnosis group (61.26%). 3. According to the blood test, the dampness-phlegm tongue diagnosis group showed higher in total cholesterol, HDL cholesterol, LDL cholesterol and triglyceride than the control group. 4. Total cholesterol and HDL cholesterol were significant higher in dampness-phlegm tongue diagnosis than the control group. Conclusion : According to the analysis, the relationship between the tongue diagnosis of dampness-phlegm and hyperlipidemia in acute stroke patients were more clarified. Based on these results, more prospective studies are to be done with more clinical data.

Experimental study of vibration characteristics of FRP cables based on Long-Gauge strain

Qi Xia,JiaJia Wu,XueWu Zhu,Jian Zhang 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.6

Steel cables as the most important components are widely used in the certain types of structures such as cablesupported bridges, but the long-span structures may result in an increase in fatigue under high stress and corrosion of steel cables. The traditional steel cable is becoming a more evident hindrance. Fiber Reinforced Polymer (FRP) cables with lightweight, high-strength are widely used in civil engineering, but there is little research in vibrational characteristics of FRP cables, especially on the damping characteristic. This article studied the two methods to evaluate dynamical damping characteristic of basalt FRP(BFRP) and glass FRP(GFRP) cables. First, the vibration tests of the B/G FRP cables with different diameter and different cable force were executed. Second, the cables forces were calculated using dynamic strain, static strain and dynamic acceleration respectively, which were further compared with the measured force. Third, experimental modal damping of each cables was calculated by the half power point method, and was compared with the calculation by Rayleigh damping theory and energy dissipation damping theory. The results indicate that (1) The experimental damping of FRP cables decreases with the increase of cable force, and the trend of experimental damping changes is roughly similar with the theoretical damping. (2) The distribution of modal damping calculated by Rayleigh damping theory is closer to the experimental results, and the damping performance of GFRP cables is better than BFRP cables.