Tianyou Tao

Simulation Study on Train-Induced Vibration Control of a Long-Span Steel Truss Girder Bridge by Tuned Mass Dampers

Train-induced vibration of steel truss bridges is one of the key issues in bridge engineering. This paper talks about the application of tuned mass damper (TMD) on the vibration control of a steel truss bridge subjected to dynamic train loads. The Nanjing Yangtze River Bridge (NYRB) is taken as the research object and a recorded typical train load is included in this study. With dynamic finite element (FE) method, the real-time dynamic responses of NYRB are analyzed based on a simplified train-bridge time-varying system. Thereinto, two cases including single train moving at one side and two trains moving oppositely are specifically investigated. According to the dynamic characteristics and dynamic responses of NYRB, the fourth vertical bending mode is selected as the control target and the parameter sensitivity analysis on vibration control efficiency with TMD is conducted. Using the first-order optimization method, the optimal parameters of TMD are then acquired with the control efficiency of TMD, the static displacement of Midspan, expenditure of TMDs, and manufacture difficulty of the damper considered. Results obtained in this study can provide references for the vibration control of steel truss bridges.

Comparative Study of the Wind Characteristics of a Strong Wind Event Based on Stationary and Nonstationary Models

AbstractInherent time-varying trends of wind records are frequently captured in recent field measurements of tropical cyclones. These observations indicate a nonstationary process that deviates fro...

Influence of apparent wave velocity on seismic performance of a super-long-span triple-tower suspension bridge

As one of the main characteristics of seismic waves, apparent wave velocity has great influence on seismic responses of long-span suspension bridges. Understanding these influences is important for seismic design. In this article, the critical issues concerning the traveling wave effect analysis are first reviewed. Taizhou Bridge, the longest triple-tower suspension bridge in the world, is then taken as an example for this investigation. A three-dimensional finite element model of the bridge is established in ABAQUS, and the LANCZOS eigenvalue solver is employed to calculate the structural dynamic characteristics. Traveling wave effect on seismic responses of these long-span triple-tower suspension bridges is investigated. Envelopes of seismic shear force and moment in the longitudinal direction along the three towers, relative displacements between the towers and the girder, and reaction forces at the bottoms of the three towers under different apparent wave velocities are calculated and presented in detail. The results show that the effect of apparent wave velocity on the seismic responses of triple-tower suspension bridge fluctuates when the velocity is lower than 2000 m/s, and the effects turn stable when the velocity becomes larger. In addition, the effects of traveling wave are closely related to spectral characteristics and propagation direction of the seismic wave, and seismic responses of components closer to the source are relatively larger. Therefore, reliable estimation of the seismic input and apparent wave velocity according to the characteristics of the bridge site are significant for accurate prediction of seismic responses. This study provides critical reference for seismic analysis and design of long-span triple-tower suspension bridges.

Measurement of Non-Stationary Characteristics of a Landfall Typhoon at the Jiangyin Bridge Site

The wind-sensitive long-span suspension bridge is a vital element in land transportation. Understanding the wind characteristics at the bridge site is thus of great significance to the wind- resistant analysis of such a flexible structure. In this study, a strong wind event from a landfall typhoon called Soudelor recorded at the Jiangyin Bridge site with the anemometer is taken as the research object. As inherent time-varying trends are frequently captured in typhoon events, the wind characteristics of Soudelor are analyzed in a non-stationary perspective. The time-varying mean is first extracted with the wavelet-based self-adaptive method. Then, the non-stationary turbulent wind characteristics, e.g.; turbulence intensity, gust factor, turbulence integral scale, and power spectral density, are investigated and compared with the results from the stationary analysis. The comparison highlights the importance of non-stationary considerations of typhoon events, and a transition from stationarity to non-stationarity for the analysis of wind effects. The analytical results could help enrich the database of non-stationary wind characteristics, and are expected to provide references for the wind-resistant analysis of engineering structures in similar areas.

Evolutionary power spectral density analysis on the wind-induced buffeting responses of Sutong Bridge during Typhoon Haikui:

Recent field measurements on long-span bridges during typhoon events have captured strong nonstationary features in the buffeting responses. In this study, the buffeting responses of Sutong Bridge during Typhoon Haikui in 2012 recorded by structural health monitoring system are analyzed to represent the nonstationary characteristics. As an accurately measured state variable, the acceleration response of the main girder is first selected to evaluate its own original stationarity in different time intervals using the run test method. The acceleration response of the main girder can be regarded as a zero-mean nonstationary random process which is in demand to extract its transient features in time–frequency domain. Hence, the evolutionary power spectral density (EPSD) of the acceleration responses, which can present the local turbulence energy distribution in both frequency and time domains, is estimated using the wavelet-based method. Also, an average wavelet spectrum is obtained by averaging the square values of wavelet coefficients along the time axis, and the comparison between the average wavelet spectrum and Fourier spectrum shows a great conformance which indirectly verifies the validity of the obtained evolutionary power spectral density. The results of this study exhibit that there are strong nonstationary characteristics existing in the buffeting responses of Sutong Bridge during Typhoon Haikui, and it is essential to incorporate the nonstationary features of winds in the analysis or design of long-span bridges from an aerodynamic viewpoint.

Parametric study on buffeting performance of a long-span triple-tower suspension bridge

Abstract The triple-tower suspension bridge is a brand new type of structural form that is equipped with a dominant mid-tower. The dynamic characteristics of this multiple main-span suspension bridge present a significant difference with that of the conventional single main-span suspension bridge. Hence, taking the Taizhou Yangtze River Bridge as an example, the buffeting performance of a long-span triple-tower suspension bridge under strong winds is comprehensively investigated via finite element method. Specifically, the sensitivity of structural buffeting performance to some major structural parameters, aerodynamic parameters as well as parameters of turbulence inputs is analysed in time domain. It was found that the structural buffeting performance heavily depends on the dead load of the main girder, sag-to-span ratio of the main cable, longitudinal stiffness and structural type of the mid-tower. Also, appropriate selection of aerodynamic admittance function, power spectrum model of fluctuating wind and the spatial coherence coefficient is important in the buffeting analysis. Besides, the self-excited forces have small impact on the calculation of buffeting responses of such a bridge. The analytical results can provide references for the buffeting analyses and wind-resistant design of similar long-span triple-tower suspension bridges.