• Energy Research

The main idea of a hinged-deck cross-section cable-stayed bridge appears with the need of increasing the capacity of a simple bridge by adding to lateral extension decks to the main deck. An experimental wind tunnel campaign to analyse the aeroelastic behaviour of a hinged-deck cross-section cable-stayed bridge has been performed. The bridge cross-section under study is formed by three parts: a central deck and two lateral extension decks joined to the central one using hinges and supported by their respective cable systems. The experimental model used is a reduced 6 degrees of freedom (DOFs) model for the elastic problem, which has previously proved to give good results concerning the bridge behaviour. The number of DOFs induces a new complexity in the oscillating motion of the bridge deck, compared to classical single deck 2 DOFs configurations. In this work, the aeroelastic tests performed at the UPM/IDR ACLA-16 wind tunnel facility to address the effect of wind barriers on the aeroelastic characteristics of the bridge section are reported. Nominal barriers are considered and compared with the case with no barriers. The effect of barrier porosity (wind barriers of the central deck and lateral decks) is also analysed. Stability ranges are reported in terms of reduced wind speed. The results show the large influence of the barriers in controlling the aeroelastic characteristics of the bridge. In some configurations, a large increase in bridge stability has been found due to the relevant effect of the barriers in changing the flow around the bridge.

Abstract An experimental investigation of instabilities of a cable-stayed bridge using wind tunnel tests is considered. The bridge deck is composed of three parts: the central deck, and two extensions, one at each side. These extensions can rotate around hinges placed at the central deck edges. The central deck and the extension decks are supported by their respective cable system. Performing a sectional test of a rigid bridge section only two DOF should be considered. However, here, 6 DOF should be considered in the modelling of the elastic problem. This is a reduced model based on a FEM model of the whole bridge, and is the base for the design of the wind tunnel tests. Aeroelastic tests have been performed in the IDR ACLA-16 wind tunnel. The influence of the angle of attack of the windward extension deck on the bridge stability has been studied. The complexity of the bridge deck motion is described considering both the oscillation frequencies and the modal shapes. Stability ranges are presented in terms of reduced wind speed and compared to other long span bridges. In a configuration, the stability range achieved is more than twice that of a similar bridge.

Abstract Bird protection barriers on high speed train bridges may have an impact on the aerodynamic and aeroelastic behaviour of these structures. On the aerodynamic static loads on the bridge deck, the conclusion is that the most porous barriers (barriers with handrails) do not modify substantially the aerodynamic loads; however, barriers with solid screens increase the intensity of these loads, in some cases significantly. No significant difference is found between barriers with straight or curved tubes. Regarding the static load on the train, only barriers with acoustic protection screens decrease the lateral load and the turning moment significantly. Again, no significant difference is found between barriers with straight or curved tubes. Finally, concerning the effect of the barriers on the air flow on the catenaries, the conclusion is that barriers with solid screen produce a very intense perturbation in this flow, both in the windward and leeward catenaries. On the contrary, the barriers with handrails (porous) practically do not alter the flow on the catenaries.

Parabolic reflectors, also known as parabolic troughs, are widely used in solar thermal power plants. This kind of power plants is usually located on desert climates, where the combined action of wind and dust can be of paramount importance. In some cases it becomes necessary to protect these devices from the joined wind and sand action, which is normally accomplished through solid windbreaks. In this paper the results of a wind tunnel test campaign, of a scale parabolic trough row having different windward windbreaks, are reported. The windbreaks herein considered consist of a solid wall with an upper porous fence. Different geometrical configurations, varying the solid wall height and the separation between the parabolic trough row and the windbreak have been considered. From the measured time series, both the mean and peak values of the aerodynamic loads were determined. As it would be expected, mean aerodynamic drag, as well as peak values, decrease as the distance between the windbreak and the parabolic increases, and after a threshold value, such drag loads increase with the distance.