Buffet loading, dynamic response and aerodynamic control of a suspension bridge in a turbulent wind

Abstract

This paper describes experiments relating to the buffet response and control of a section of a long-span suspension bridge deck elastically mounted as part of a wind tunnel experiment. The bridge section is subject to grid generated flow turbulence. Two grids are used -one is a standard biplanar grid, while the second is a new design that provides larger turbulence length scales. The buffet response results are compared with admittances calculated using unsteady, three-dimensional, lifting-surface theory that extends standard two-dimensional Sears' theory. The bridge deck heave and pitch responses are predicted with comparisons made with wind tunnel measurements. In order to suppress buffeting, and increase the deck's critical flutter speed, the deck model is fitted with controllable leading-and trailing-edge flaps. Two sets of passive controllers, which use the flap angles as the control inputs, are demonstrated and evaluated for their capability to suppress the buffet response of the deck and increase its critical flutter speed. The first set of controllers sense the deck's position (pitch angle and heave, or pitch angle alone), whilst the second set (which are mechanical controllers) sense the vertical velocity of the flap hinge points. The control system design problem is solved as a mixed H 2 /H ∞ optimisation problem. The wind tunnel experPreprint submitted to Fluids and Structures June 14, 2016 iments show that these control systems can reduce considerably the deck's buffet response, whilst simultaneously increasing its critical flutter speed.

Buffeting performance of long-span suspension bridge based on measured wind data in a mountainous region

“…Outer environment conditions more correspond to the reality and considered such astopography, extreme value of typhoon, turbulent spatial correlation coefficient, skew wind, design and measured power spectrum, non-stationary and stochastic excitation [2,5,[18][19][20][21][22][23][24][25]. Improved analysis theories were applied in the buffeting performance including linear and non-linear regression analysis, evolutionary power spectral density, varying frequency-increment sweeping method, three-dimensional simulation [19,21,24,[26][27][28][29][30].…”

Experimental Aerodynamic Control of a Long-Span Suspension Bridge Section Using Leading- and Trailing-Edge Control Surfaces

“…The growth of both the pitch and heave displacements due to the flutter instability is also noisier due to superimposed buffet-induced motions. Controllers specifically designed to alleviate buffetinduced forces have also been tested for flutter suppression and are discussed in detail elsewhere [31]. Each of the four controllers in Table II were tested for a range of super-critical wind-speeds.…”

Vortex moment map for unsteady incompressible viscous flows

“…An understanding of the dynamic variation of pitching moment is key to analyzing a range of dynamic problems, including buffeting of long-span suspension bridges (Zhao et al 2016), the phenomenon of stall flutter on helicopters (Ham & Maurice 1966) and wind turbines (Hansen 2007), as well as flapping flight (Krashanitsa et al 2009) particularly when the wings or lifting sections are very flexible in torsion. In these cases which involve either bluff bodies or leading-edge separation, the unsteady effect of the pitching moment can play a very important role in the stability and dynamic response of the body when coupled to the effects of structural compliance or rigid-body dynamics (Ham & Maurice 1966).…”