Influence of cable loosening on nonlinear parametric vibrations of inclined cables

Qingxiong Wu,Kazuo Takahashi,Baochun Chen 국제구조공학회 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.2

The effect of cable loosening on the nonlinear parametric vibrations of inclined cables is discussed in this paper. In order to overcome the small-sag limitation in calculating loosening for inclined cables, it is necessary to first derive equations of motion for an inclined cable. Using these equations and the finite difference method, the effect of cable loosening on the nonlinear parametric response of inclined cables under periodic support excitation is evaluated. A new technique that takes into account flexural rigidity and damping is proposed as a solution to solve the problem of divergence. The regions of inclined cables that undergo compression are also indicated.

Dynamic characteristics of cable vibrations in a steel cable-stayed bridge using nonlinear enhanced MECS approach

Wu, Qingxiong,Takahashi, Kazuo,Chen, Baochun Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.1

This paper focuses on the nonlinear vibrations of stay cables and evaluates the dynamic characteristics of stay cables by using the nonlinear enhanced MECS approach and the approximate approach. The nonlinear enhanced MECS approach is that both the girder-tower vibrations and the cable vibrations including parametric cable vibrations are simultaneously considered in the numerical analysis of cable-stayed bridges. Cable finite element method is used to simulate the responses including the parametric vibrations of stay cables. The approximate approach is based on the assumption that cable vibrations have a small effect on girder-tower vibrations, and analyzes the local cable vibrations after obtaining the girder-tower responses. Under the periodic excitations or the moderate ground motion, the differences of the responses of stay cables between these two approaches are evaluated in detail. The effect of cable vibrations on the girder and towers are also discussed. As a result, the dynamic characteristics of the parametric vibrations in stay cables can be evaluated by using the approximate approach or the nonlinear enhanced MECS approach. Since the different axial force fluctuant of stay cables in both ends of one girder causes the difference response values between two approach, it had better use the nonlinear enhanced MECS approach to perform the dynamic analyses of cable-stayed bridges.

Analysis of local vibrations in the stay cables of an existing cable-stayed bridge under wind gusts

Wu, Qingxiong,Takahashi, Kazuo,Chen, Baochun Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.5

This paper examines local vibrations in the stay cables of a cable-stayed bridge subjected to wind gusts. The wind loads, including the self-excited load and the buffeting load, are converted into time-domain values using the rational function approximation and the multidimensional autoregressive process, respectively. The global motion of the girder, which is generated by the wind gusts, is analyzed using the modal analysis method. The local vibration of stay cables is calculated using a model in which an inclined cable is subjected to time-varying displacement at one support under global vibration. This model can consider both forced vibration and parametric vibration. The response characteristics of the local vibrations in the stay cables under wind gusts are described using an existing cable-stayed bridge. The results of the numerical analysis show a significant difference between the combined parametric and forced vibrations and the forced vibration.

Using cable finite elements to analyze parametric vibrations of stay cables in cable-stayed bridges

Wu, Qingxiong,Takahashi, Kazuo,Chen, Baochun Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.23 No.6

This paper uses the finite element method to simultaneously consider the coupled cable-deck vibrations and the parametric vibrations of stay cables in dynamic analysis of a cable-stayed bridge. The stay cables are represented by some cable finite elements, which can consider the parametric vibration of the cables. In addition to modeling stay cables using multiple link cable elements, a procedure for removing the self-weight term of cable element is proposed. A eigenvalue analysis process using dynamic condensation method for sorting out the natural modes of the girder-tower vibrations and the Rayleigh damping considering element damping for damping matrix are also proposed for dynamic analyses of cable-stayed bridges. The possibilities of using cable elements and of using global and local vibrations to evaluate the parametric vibrations of stay cables in a cable-stayed bridge are confirmed, respectively.

Influence of cable loosening on nonlinear parametric vibrations of inclined cables

Wu, Qingxiong,Takahashi, Kazuo,Chen, Baochun Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.2

The effect of cable loosening on the nonlinear parametric vibrations of inclined cables is discussed in this paper. In order to overcome the small-sag limitation in calculating loosening for inclined cables, it is necessary to first derive equations of motion for an inclined cable. Using these equations and the finite difference method, the effect of cable loosening on the nonlinear parametric response of inclined cables under periodic support excitation is evaluated. A new technique that takes into account flexural rigidity and damping is proposed as a solution to solve the problem of divergence. The regions of inclined cables that undergo compression are also indicated.

Analysis of local vibrations in the stay cables of an existing cable-stayed bridge under wind gusts

Qingxiong Wu,Kazuo Takahashi,Baochun Chen 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.5

This paper examines local vibrations in the stay cables of a cable-stayed bridge subjected to wind gusts. The wind loads, including the self-excited load and the buffeting load, are converted into time-domain values using the rational function approximation and the multidimensional autoregressive process, respectively. The global motion of the girder, which is generated by the wind gusts, is analyzed using the modal analysis method. The local vibration of stay cables is calculated using a model in which an inclined cable is subjected to time-varying displacement at one support under global vibration. This model can consider both forced vibration and parametric vibration. The response characteristics of the local vibrations in the stay cables under wind gusts are described using an existing cable-stayed bridge. The results of the numerical analysis show a significant difference between the combined parametric and forced vibrations and the forced vibration.

Dynamic Characteristics of Megami Cable-stayed Bridge- A Comparison of Experimental and Analytical Results-

Qingxiong Wu,Yuichi Kitahara,Kazuo Takahashi,Baochun Chen 한국강구조학회 2008 International Journal of Steel Structures Vol.8 No.1

The Megami Bridge, with a main span of 480 m, is the 6th longest cable-stayed bridge in Japan. A comparison of experimental and analytical modal analysis is performed to determine the dynamic characteristic of this bridge. The ambient vibration test is carried out using very few accelerometers. Parameter identification is carried out using the stochastic subspacebased identification (SSI) method in the time-domain as proposed by Katayama. The SSI method used in this paper can be used for estimating the modal properties of a long span cable-stayed bridge by comparing with the maximum entropy method(MEM). Furthermore, the effectiveness of the tuned mass dampers (TMDs) used in the bridge is evaluated through a human excitation test. Logarithmic damping is about 0.030 when the TMD is activated, a little higher than the design value 0.026, so proving that the TMDs are effective. Finally, the analytical eigenvalues obtained from finite element analysis agree well with the experimental values, thus verifying the analytical model.

An experimental and numerical study on temperature gradient and thermal stress of CFST truss girders under solar radiation

Guihan Peng,Shozo Nakamura,Xinqun Zhu,Qingxiong Wu,Hailiang Wang 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.5

Concrete filled steel tubular (CFST) composite girder is a new type of structures for bridge constructions. The existing design codes cannot be used to predict the thermal stress in the CFST truss girder structures under solar radiation. This study is to develop the temperature gradient curves for predicting thermal stress of the structure based on field and laboratory monitoring data. An in-field testing had been carried out on Ganhaizi Bridge for over two months. Thermal couples were installed at the cross section of the CFST truss girder and the continuous data was collected every 30 minutes. A typical temperature gradient mode was then extracted by comparing temperature distributions at different times. To further verify the temperature gradient mode and investigate the evolution of temperature fields, an outdoor experiment was conducted on a 1:8 scale bridge model, which was installed with both thermal couples and strain gauges. The main factors including solar radiation and ambient temperature on the different positions were studied. Laboratory results were consistent with that from the in-field data and temperature gradient curves were obtained from the in-field and laboratory data. The relationship between the strain difference at top and bottom surfaces of the concrete deck and its corresponding temperature change was also obtained and a method based on curve fitting was proposed to predict the thermal strain under elevated temperature. The thermal stress model for CFST composite girder was derived. By the proposed model, the thermal stress was obtained from the temperature gradient curves. The results using the proposed model were agreed well with that by finite element modelling.

Experimental study on the compression of concrete filled steel tubular latticed columns with variable cross section

Yan Yang,Jun Zhou,Jiangang Wei,Lei Huang,Qingxiong Wu,Bao-chun Chen 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.3

The effects of slenderness ratio, eccentricity and column slope on the load-carrying capacities and failure modes of variable and uniform concrete filled steel tubular (CFST) latticed columns under axial and eccentric compression were investigated and compared in this study. The results clearly show that all the CFST latticed columns with variable cross section exhibit an overall failure, which is similar to that of CFST latticed columns with a uniform cross section. The load-carrying capacity decreases with the increase of the slenderness ratio or the eccentricity. For 2-m specimens with a slenderness ratio of 9, the ultimate load-carrying capacity is increased by 3% and 5% for variable CFST latticed columns with a slope of 1:40 and 1:20 as compared with that of uniform CFST latticed columns, respectively. For the eccentrically compressed variable CFST latticed columns, the strain of the columns at the loading side, as well as the difference in the strain, increases from the bottom to the cap, and a more significant increase in strain is observed in the cross section closer to the column cap.