Flutter control effect and mechanism of central-slotting for long-span bridges

Abstract

The flutter control effect and mechanism of central-slotting, which have gradually been adopted in the design and construction of long-span bridges as an effective flutter controlling measure, were investigated with theoretical analysis and wind tunnel test. Five basic girder cross-sections representing five typical aerodynamic configurations were selected and central-slotted with two different slot widths. Then, a series of sectional model tests and theoretical analyses based on the two-dimensional three-degrees-offreedom coupling flutter analysis method (2 dimension-3 degrees of freedom method, 2d-3DOF method) were carried out to investigate the aerodynamic performance, flutter mechanism and flutter modality of the five basic sections and their corresponding central-slotted sections. The results show that central-slotting can not always improve the aerodynamic stability of bridge structure. The control effect of central-slotting depends on the aerodynamic configuration of the original girder section and the corresponding central-slotting width. If the original section is inappropriate or the slot width is unsuitable, central-slotting will even deteriorate the structural flutter performance. Theoretical investigations indicated that the differences in flutter control effects come from the different formation and evolution of aerodynamic damping, and flutter modality especially the participation level of heaving motion also has a significant influence on the control effect of central-slotting.

On the effects of the gap on the unsteady pressure characteristics of two-box bridge girders

“…22 and 29), meaning that, regardless of the gap length, rather the existence of the gap itself controls these parameters; H Ã 2 , A Ã 1 and A Ã 3 are better correlated with the original Theodorsen function (Eqs. (11), (14) and (16)), independently of the gap length. As for H Ã 4 , the values exhibit an independent behavior.…”

“…The mechanisms of such aerodynamic stabilization, however, have not been fully clarified [12][13][14]. Depending on the characteristics of the deck as a whole and the gap length, flutter onset may even decrease [13,14].…”

“…Depending on the characteristics of the deck as a whole and the gap length, flutter onset may even decrease [13,14]. Analyses to determine correlations with the characteristics of one of the boxes were attempted by Yang et al [14], leading to the conclusion that central-slotting is not always able to improve the stability, which would depend on the aerodynamic characteristics of that single-box and the gap length. When gratings are used, the situation becomes even complicated, since the effects of gratings have been shown to depend on Reynold's number [5,15,16].…”

Flutter performance and aerodynamic mechanism of plate with central stabilizer at large angles of attack

“…Chen et al (2006) investigated the mechanism of a vertical stabilizer for improving the aerodynamic stability of an open deck II-shaped section and a closed box section and found that vertical stabilizer can increase the amplitude of the heaving motion and decrease that of the rotational motion of the bridge decks. Yang et al (2007) indicated that the use of a central stabilizer with an appropriate height can improve the aerodynamic stability, but the aerodynamic stability decreases when the height of the stabilizer exceeds the critical limit. Ouyang and Chen (2016) showed that the central stabilizer promotes the formation of vortex pairs at the upper and lower decks near the center of the bridge deck by computational fluid dynamics (CFD) numerical simulation and particle image velocimetry (PIV) wind tunnel tests and enhances the participation function of the heaving motion of the bridge.…”

Study on the Effect and Mechanism of Aerodynamic Measures for the Vortex-Induced Vibration of Separate Pairs of Box Girders in Cable-Stayed Bridges

“…In this paper, we discussed the effects of different aerodynamic measures on the VIV of separate pairs of box girders through a wind tunnel test and tried to explain their control mechanism by using the Computational Fluent Dynamics (CFD) technology. Compared to the closed box girders, the flutter stability of the separate pair of box girders has been improved significantly, which, however, is compensated by high VIV possibility [29,30]. In order to restrain the VIV of the bridge with separate pairs of box girders, it is important to choose an appropriate aerodynamic configuration.…”