Stability of a suspension bridge with a localized structural damping

<p style='text-indent:20px;'>Strong vibrations can cause lots of damage to structures and break materials apart. The main reason for the Tacoma Narrows Bridge collapse was the sudden transition from longitudinal to torsional oscillations caused by a resonance phenomenon. There exist evidences that several other bridges collapsed for the same reason. To overcome unwanted vibrations and prevent structures from resonating during earthquakes, winds, ..., features and modifications such as dampers are used to stabilize these bridges. In this work, we use a minimum amount of dissipation to establish exponential decay- rate estimates to the following nonlocal evolution equation</p><p style='text-indent:20px;'><disp-formula> <label/> <tex-math id="FE1"> \begin{document}$ u_{tt}(x,y,t)+\Delta^2 u(x,y,t) - \phi(u) u_{xx}- \left(\alpha(x, y) u_{xt}(x,y,t)\right)_x = 0, $\end{document} </tex-math></disp-formula></p><p style='text-indent:20px;'>which models the deformation of the deck of either a footbridge or a suspension bridge.</p>

Three-dimensional FSI Simulation by Using a Novel Hybrid Scaling – Application to the Tacoma Narrows Bridge

In this paper a novel fluid-structure interaction approach for simulating flutter phenomenon is presented. The method is capable of modelling the structural motion and the fluid flow coupling in a fully three-dimensional manner. The key step of the proposed FSI procedure is a hybrid scaling of the physical fields; certain properties of the CFD simulation are scaled, while those of the mechanical system are kept original. This kind of scaling provides a significant speedup, since the number of the costly CFD time steps can be remarkably reduced. The acceptable computational time makes it possible to consider complex engineering problems such as buffeting, vortex shedding or flutter of a bridge deck or a wing of an airplane.

Eccentric-wing flutter stabilizer – Simplified analysis and main findings

<p>A device aiming at preventing bridge flutter is studied. It consists of fixed wings positioned with a large lateral offset along the edges of the bridge deck. The wings are attached to the bridge deck by means of lateral support structures. Flutter analyses for various kinds of bridges and wind-tunnel tests confirm the flutter-suppression effectiveness of the wings. They constitute a passive damping device without moving parts. This is an advantage over devices with moving parts, which meet resistance due to reliability and maintenance concerns. The main findings to date concerning analysis, flutter-suppression effectiveness, and cost-efficiency of the eccentric-wing flutter stabilizer are summarized. In addition, a simplified approach for the analysis of torsional flutter of a bridge equipped with this device is presented and applied to the first Tacoma Narrows Bridge. It is found that with relatively small effort the flutter stability of that bridge could have been substantially improved.</p>

The Tradeoffs of Tolling Untolled Roads

Recent years have seen increasing study and implementation of imposing tolls on existing untolled roadway capacity. This is due to growing agency budgetary challenges, increasing infrastructure needs, and some easing of legislative restrictions and pilot-project opportunities to add tolls to untolled roads. This paper presents a summary of current policy, profiles of facilities in operation, and a discussion of common tradeoffs related to tolling untolled roads. The facilities included are the Port Mann Bridge, Snapper Creek Expressway, Ohio River Bridges, Dominion Boulevard, Downtown Tunnel, Midtown Tunnel, SR 520 Bridge, and Tacoma Narrows Bridge. The tradeoffs discussed include those related to traffic diversion, the argument that untolled roads have already been paid for, that new toll payers may be unfamiliar with how to pay, equity, how tolling provides acceleration of project implementation and a dedicated funding source, and all-electronic tolling. Considering traffic diversion, the facilities included in the study were found to have from 10% to 36% less traffic after tolling, with most in the range of 15% to 25% less. Considering project acceleration, tolling on all facilities was established to fund major improvement projects that likely would not have been possible without toll revenue. Given consideration of all tradeoffs, it is important to take a long-term approach to toll project evaluation.