Dynamic Characteristics Of Cable-stayed Bridge Research Articles

Modal Analysis of a Steel Truss Girder Cable-Stayed Bridge with Single Tower and Single Cable Plane

The dynamic characteristics of bridge structures are important in wind stability analysis, seismic design, fatigue assessment, health inspection, and maintenance of bridge structures; however, the mechanical and dynamic properties of different bridge types are different. A long-span cable-stayed bridge has the advantages of large flexibility, long natural vibration period, low natural frequency, dense spectrum, and denser modal than those of general structures. In this paper, the dynamic characteristics of a cable-stayed bridge with single pylon and single cable plane in the maximum cantilever stage and the complete bridge are analyzed. The single-tower cable-stayed bridge has some unique characteristics, such as lower cost, and a more beautiful appearance, but its torsional rigidity is lower, which increases the risk of wind damage and earthquake damage. Therefore, a finite element analysis of this bridge in the maximum cantilever state is carried out, and the influences of the main components’ rigidity, the inclination angles of the stayed cables, the supporting conditions, and the locations of the auxiliary piers are analyzed for the sustainability of this type of cable-stayed bridge. The analysis results show that a cable-stayed bridge with single pylon and single cable plane has more flexibility, and that the lateral rigidity and torsional rigidity are smaller. Structure rigidity, dip angles of the stayed cables, and positions of the auxiliary piers all have significant influences on the dynamic characteristics of cable-stayed bridges.

Effectiveness of Soil–Structure Interaction and Dynamic Characteristics on Cable-Stayed Bridges Subjected to Multiple Support Excitation

The purpose of the study is to determine the effects of multiple support excitations (MSE) and soil–structure interaction (SSI) on the dynamic characteristics of cable-stayed bridges founded on pile foundation groups. In the design of these structures, it is important to consider the effects of spatial variability of earthquake ground motions. To do this, the time histories of the ground motions are generated based on the spatially varying ground motion components of incoherence, wave-passage, and site-response. The effects of SSI on the response of a bridge subjected to the MSE are numerically illustrated using a three-dimensional model of Quincy Bayview cable-stayed bridge in the USA. The soil around the pile is linearly elastic, homogeneous isotropic half space represented by dynamic impedance functions based on the Winkler model of soil reaction. Structural responses obtained from the dynamic analysis of the bridge system show the importance of the SSI and the MSE effects on the dynamic responses of cable-stayed bridges.

Three-dimensional finite element modelling of long-span cable-stayed bridges

Finite element (FE) modelling is a prominent way to simulate both static and dynamic characteristics of cable-stayed bridges to understand their structural complexities. Many initial FE models have not been successful in the analysis of the structural behaviour of cable-stayed bridges. This paper presents the details of an updated FE modelling procedure for long-span cable-stayed bridges. The design information of Tatara Bridge with an 850-m main span is considered for numerical studies. The dynamic properties of the FE model, including mode shapes and natural frequencies, are compared with field vibration test results to validate the presented modelling process. Sensitivity analysis of structural parameters is also applied to update effective parameters and understand the structural behaviour of the bridge. The new and beneficial aspects presented in this paper regarding FE modelling procedure and finding effective material and structural parameters will be useful for future design and analysis of cable-...

Statistical Analysis of Basic Dynamic Characteristics of Large Span Cable-Stayed Bridge Based on High Order Perturbation Stochastic FEM

With the quick development of transportation in China, long span cable-stayed bridges have been widely constructed to cross large rivers and deep canyons attribute to their unique structural forms and mechanical properties. For large-scale cable-stayed bridges, how to determine their basic dynamic characteristics or modal data is an important issue on the dynamic analysis of bridge structures. Noting the uncertainty of structural parameters or geometric shape, it is also of significance to find out the statistic dynamic characteristics of uncertain long span cable-stayed bridges. At the present paper, different from traditional low order perturbation stochastic approach, a high order perturbation stochastic FEM called as recursive stochastic finite element method was employed, which is a good practical approximation method compared to the Monte Carlo simulation method. Taking Edong Yangtze River Bridge as a research objective, the recursive stochastic finite element method was employed to solve the modal data of large span cable-stayed bridge with random parameters. Firstly, in the non-orthogonal polynomial presentation, natural frequencies and mode shapes of the random cable-stayed bridge were expressed. Then coefficients of the non-orthogonal polynomial expansion are able to be determined through high order perturbation technique. On the basis of the coefficients obtained, the probability density functions and statistic characteristics of the modal data were straightforward to implement. In accordance with detailed analyzations and discussions on the basic dynamic characteristics of the cable-stayed bridge, it can be found that the randomness of sectional flexural stiffness of the deck beam and bridge towers is very sensitive to many modes of Edong Yangtze River Bridge. However, the elastic stiffness simulating the pile-soil interaction has less influence on the in-plane modes.

Sensitivity Analysis of the Influence of Structural Parameters on Dynamic Behaviour of Highly Redundant Cable-Stayed Bridges

The model tuning through sensitivity analysis is a prominent procedure to assess the structural behavior and dynamic characteristics of cable-stayed bridges. Most of the previous sensitivity-based model tuning methods are automatic iterative processes; however, the results of recent studies show that the most reasonable results are achievable by applying the manual methods to update the analytical model of cable-stayed bridges. This paper presents a model updating algorithm for highly redundant cable-stayed bridges that can be used as an iterative manual procedure. The updating parameters are selected through the sensitivity analysis which helps to better understand the structural behavior of the bridge. The finite element model of Tatara Bridge is considered for the numerical studies. The results of the simulations indicate the efficiency and applicability of the presented manual tuning method for updating the finite element model of cable-stayed bridges. The new aspects regarding effective material and structural parameters and model tuning procedure presented in this paper will be useful for analyzing and model updating of cable-stayed bridges.

Soil–structure interaction analysis of cable-stayed bridges for spatially varying ground motion components

In this study, it is intended to determine the effects of soil–structure interaction (SSI) and spatially varying ground motion on the dynamic characteristics of cable-stayed bridges. For this purpose, ground motion time histories are simulated for spatially varying ground motions, depending on its components of incoherence, wave-passage and site-response effects. The substructure method, which partitions the total soil–structure system into the structural system and the soil system, is used to treat the soil–structure interaction problem. To emphasize the relative importance of the spatial variability effects of earthquake ground motion, bridge responses are determined for the fixed base bridge model, which neglects the soil–structure interaction (no SSI) and for the bridge model including the soil–structure interaction (SSI). This parametric study concerning the relative importance of the soil–structure interaction and spatially varying ground motion shows that these effects should be considered in the dynamic analyses of cable-stayed bridges.

Influence of Pile-Soil-Structure Interaction on the Dynamic Characteristics of Cable-Stayed Bridge

The dynamic characteristics of cable-stayed bridge will be affected greatly by soil action. In the paper, a spatial dynamic analysis model of a cable-stayed bridge was built by using the general finite element software ANSYS. The dynamic characteristics of the frequencies and modal shapes are investigated and compared with considering the pile-soil-structure interaction or not. From the analysis, the results indicate that if the pile-soil-structure interaction is taken into account, there will have a significant effect on the dynamic behaviors of bridge.

Effects of partially earth-anchored cable system on dynamic wind response of cable-stayed bridges

In this study, a partially earth-anchored cable system is studied in order to reduce the dynamic wind response of cable-stayed bridges. The employment of earth-anchored cables changes the dynamic characteristics of cable-stayed bridges under wind loads. In order to estimate the changes in the member forces, the spectral analysis for wind buffeting loads are performed and the peak responses are evaluated using 3-D finite element models of the three-span cable-stayed bridges with the partially earth-anchored cable system and with the self-anchored cable system, respectively. Comparing the results for the two different models, it is found that the earth-anchored cables affect longitudinal and vertical modes of the bridge. The changes of the natural frequencies for the longitudinal modes remarkably decrease the peak bending moment in the pylon and the movements at the expansion joints. The small changes of the natural frequencies for the vertical modes slightly increase bending moments and deflections in the girder. The original effects of the partially earth-anchored cable system are also shown under wind loads; the decrement of girder axial forces and bearing uplifting forces, and the increment of cable forces in the earth-anchored cables.

Modeling of cable vibration effects of cable-stayed bridges

The analysis of dynamic responses of cable-stayed bridges subjected to wind and earthquake loads generally considers only the motions of the bridge deck and pylons. The influence of the stay cable vibration on the responses of the bridge is either ignored or considered by approximate procedures. The transverse vibration of the stay cables, which can be significant in some cases, are usually neglected in previous research. In the present study, a new three-node cable element has been developed to model the transverse motions of the cables. The interactions between the cable behavior and the other parts of the bridge superstructure are considered by the concept of dynamic stiffness. The nonlinear effect of the cable caused by its self-weight is included in the formulation. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed model. The impact of cable vibration behavior on the dynamic characteristics of cable-stayed bridges is discussed.