Flutter characteristics of twin-box girder bridges with vertical central stabilizers

Abstract

It has been well known that Vertical Central Stabilizers (VCS) have the potential of improving flutter performance of long-span bridges. However, the fundamental flutter mechanisms of VCS are still not fully understood so far. In this study, a series of windtunnel tests involving the combination of six representative heights and four types of VCS were conducted to fundamentally investigate the influence of VCS on flutter performance of twin-box girders with various Slot Width Ratios (SWRs). Experimental results show that the flutter instability of 20% SWR is significantly sensitive to the height change of VCS, whereas the VCS have little effect on the flutter performance for 80% and 100% SWR. In addition, the results from Two-Dimensional Three Degree of freedom (2D-3DOF) flutter analysis demonstrates that aerodynamic damping Part A with reference of flutter derivative A2 * makes the greatest contribution to the flutter instability for a 0.8 h/H VCS, while the role of Part D with reference of A1 * H3 * becomes critical for a short VCS (i.e. the ratio of h/H is less than 0.2). Besides, the results of Computational Fluid Dynamics simulation indicate that the geometry of VCS influence the transforming vortices' structures and pressure distribution under the central slotting. Finally, the modified Selberg formula presented in this study has the capability of predicting the critical flutter speed of twin-box girders with various SWRs and VCS.

Statistical characteristics of modal damping of long-span suspension bridge at different wind speeds

“…These results were extracted from 226 groups of acceleration series recorded at wind speeds lower than 0.5 m/s. By contrast, Table 2 also gave the FEM results calculated by Yang et al (2017) as well as with the identified results by forced vibrations tests conducted by Tan (2012).…”

A Quick Assessment and Optimization Method for a Flutter Aerodynamic Measure of a Typical Flat Box Girder

“…Based on the coupling effect of aerodynamic forces, Yang et al [4][5][6] established the relationship between torsional, vertical, and lateral vibration parameters and flutter derivatives (e.g., using the two-dimensional three-degree-of-freedom coupled flutter analysis method) and studied the flutter mechanism of two typical bridge sections: the closed box girder and two-isolated-girder sections. e flutter of these two sections is caused by negative aerodynamic damping, and the negative aerodynamic damping of the streamlined section is the result of the coupling effect of torsion and vertical motion.…”

A predictive critical flutter wind speed modeling for long-span bridges

“…For long-span bridges, the bridge deck is a relatively slender structure with a low structural damping, remarkably low rigidity, high sensitivity to wind load, and high likelihood of wind-induced flutter or galloping (Hu et al, 2015). When the wind forces against the main span gain speed gradually, the bridge deck vibration can be converted from an initial damped vibration to vibration divergence (Hu et al, 2016; Ubertini et al, 2017; Yang et al, 2017), and eventually causing structural collapse. Therefore, during the bridge design phase, accurate and effective prediction of critical flutter wind speed is imperative.…”