Computational & Technology Resources
an online resource for computational,
engineering & technology publications 

CivilComp Proceedings
ISSN 17593433 CCP: 79
PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 227
SemiActive Fuzzy Logic Control of Suspension Bridge Flutter S. Pourzeynali+ and T.K. Datta*
+Department of Civil Engineering, Engineering Faculty, The University of Guilan, Rasht, Iran
S. Pourzeynali, T.K. Datta, "SemiActive Fuzzy Logic Control of Suspension Bridge Flutter", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", CivilComp Press, Stirlingshire, UK, Paper 227, 2004. doi:10.4203/ccp.79.227
Keywords: semiactive control, fuzzy logic controller, suspension bridge, flutter.
Summary
The longspan suspension bridges due to their large flexibility, lightness, and
inherent low damping are much prone to aerodynamic flutter instability. Flutter is a
windinduced aerodynamic instability in the bridge deck at a critical wind velocity
leading to an exponentially growing response. Flutter phenomenon, normally causes
the catastrophic failure of the total bridge (Tacoma Narrows disaster, 1940).
The control of flutter by TMD systems has been studied by many researchers. Nobuto et al. [1], studied the effectiveness of the TMD control system on a sectional model of the bridge deck. Two TMDs were placed on the leading and trailing edge of the deck and their frequencies were tuned to resulting flutter frequency. The obtained improvement of the critical flutter wind speed was about 14%. Another TMD study is carried out by Pourzeynali and Datta [2], in which a combined vertical and torsional TMD system is applied to increase the critical flutter wind speed. The proposed TMD system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetric modes of the bridge, which get coupled during flutter. The maximum improvement of the critical flutter wind speed is obtained about 2.03 times the uncontrolled flutter speed for 5% TMD damping ratio. Wilde and Fujino [3] proposed an active aerodynamic control method of suppressing flutter of a very longspan bridge. The control system consists of additional control surfaces attached to the bridge deck, which are used to generate stabilizing aerodynamic forces. Although in recent years, there have been many studies on the control of coupled flutter of longspan suspension bridges as reported above; most of them use passive control devices. Recently few studies are made on the active/ semiactive control of suspension bridge flutter. In particular, use of fuzzy rule base for semi active control of suspension bridges is not reported before. In this study, a semiactive tuned mass damper (STMD) system with variable damping is used to control the flutter instability of long span suspension bridges. For this purpose, a combined vertical and torsional model of tuned mass damper (TMD) system is used. This system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetric modes of the bridge, which get coupled during flutter. The variable damping of the system is chosen through a fuzzy logic controller (FLC) system using the displacement and velocity at the center of the bridge, at which the TMD is placed, as the inputs. The transient response of the bridge due to a given initial condition in presence of the wind selfexcited forces is controlled so that critical flutter wind speed for the bridge is enhanced. The equation of motion of the suspension bridges is obtained by multimode finite element method in time domain using the energy approach and applying the Hamilton's principle. For this purpose, the entire bridge is discretized into two dimensional beam elements, each consisting of two nodes at its ends. At each node four degrees of freedom are considered, in which in final equation the degrees of bending rotation and warping displacement are condensed out. The methodology is applied to increase the flutter wind speed of the Thomas Suspension Bridge. Also, a numerical study is conducted to investigate the effectiveness of the semiactive control scheme, from which the following results are obtained:
References
purchase the fulltext of this paper (price £20)
go to the previous paper 
