Effects of horizontal splitter plates on the vortex-induced vibration and aerostatic characteristics of twin separated parallel decks for a rail-cum-road bridge

Abstract

Installing the splitter plates is a passive aerodynamic solution for eliminating vortex-induced vibration (VIV). However, the influences of splitter plates on the VIV and aerostatic performances are more complicated due to aerodynamic interference between highway and railway decks. To study the effects of splitter plates, wind tunnel experiments for measuring VIV and aerostatic forces of twin decks under two opposite flow directions were conducted, while the surrounding flow and wind pressure of static twin decks with and without splitter plates are numerically simulated. The results showed that the incoming flow direction affects the VIV response and aerostatic coefficients. The highway deck has poor vertical and torsional VIV, and the VIV region and amplitude are different under different directions. While the railway deck only has vertical VIV when located upstream. The splitter plates can impede the process of vortex generation, shedding and impinging at the gap between twin deck, and significantly reducing the surface fluctuating pressure coefficient, thus effectively suppressing the VIV of twin decks. While, the splitter plates hurt the upstream deck regarding static wind stability and have little effect on the downstream deck. The splitter plates of appropriate width are recommended to improve VIV performances in twin parallel bridges.

1. Introduction

The long-span twin parallel bridges are a unique type of rail-cum-road bridges that may greatly increase cross-straits’ capacity and enhance transportation [1, 2]. As high-speed train bridges evolve [3, 4], more and more twin parallel bridges are visible to the general public [5]. However, wind-induced response problems such as static wind stability and interactive vortex-induced vibration (VIV) of bridges caused by complex inter-gap aerodynamic disturbance effects also bring new challenges to the development of twin parallel bridges [6 −8]. In recent years, the continuous reports of VIV events make VIV gain the attention of more researchers [9, 10], who have done extensive studies on the manifestation, triggering mechanism, and vibration suppression mechanism of the VIV phenomena of large-span bridges through wind tunnel experiments, field measurements, and numerical simulations [11−22].

However, the static and dynamic wind response of the twin parallel decks, such as VIV and aerodynamic characteristics, is more complex and also worth studying, and some related studies have been explored by researchers [23−26]. It has been found that the spacing ratio, frequency ratio, and aerodynamic vibration suppression measures are the primary determining elements in the aerodynamic disturbance effect, which has a great influence on the static and dynamic wind-induced response of twin parallel decks [27 −31]. Adopting VIV suppression methods during the bridge design phase is crucial for long-span bridges [32, 33].

Aerodynamic countermeasures for passive techniques, which control vortex shedding by changing the form of the aerodynamic shape or adding extra devices to the flow, remain the most extensively employed procedures due to the dependability [34, 35], including the wind fairings, guide vanes for maintenance traces [36], grid plates [37], sealing traffic barriers at regions [18], wind barriers [38, 39], splitter plates [40, 41] and so on.

The splitter plate is one of the effective measures to control the VIV among passive controls [42, 30]. As one of the passive control aerodynamic countermeasures, the splitter plates are often used to suppress VIV of cylinder. This device was first developed by ROSHKO [43], who performed experiments in which a splitter plate was attached to the cylinder base to suppress VIV. Thin splitter plates were widely used in subsequent studies [44]. There are two kinds of installation of splitter plates, such as attached [45] and detached [42].