Long-span bridges constitute landmark projects, whose iconic impact blends together aesthetic creativity and structural competence. The simplicity of their form is contrasted by the magnitude of their scale, and the span length, in particular, relates to the structure's technical efficiency as well as to its visual impression. Simple extrapolation of rather conventional concepts, however, does not usually lead to great progress in technological development and this might prove to be the case for the aeroelastic performance of such structures as the trend to increase their slenderness continues. The aim of this work is to establish a framework for implementing control devices, primarily in the form of aerodynamic appendices, for suppressing aeroelastic instabilities and mitigating wind induced vibrations in long-span bridges. First, a simplified, sectional structural bridge model is created, and its interaction with a constant velocity airstream is analysed using thin-aerofoil theory. Two different passive control strategies are then considered, separately and in combination. The first makes use of trailing and leading-edge flaps adjacent to the bridge deck. The rotating motion of the flaps is triggered by the deck’s movement through a combination of connecting springs, dampers and the newly introduced inerter device. The second approach combines the aerodynamic stabilizing effect of the flaps with a driving force provided by a suspended mass, placed inside the box girder. For both strategies, special attention is given to ensuring that the proposed passive control system attains optimum robustness margins, that is, maximum tolerance to the uncertainties which accompany any physical system. The analysis is then generalized by extending it to a discretized bridge aeroelastic model, which considers full multimodal interaction. The structural component of the modelling makes use of a reduced-size finite element formulation, in which the contribution of both the girder and the main cables is combined into single ...
Active and passive aeroelastic control of long-span suspension bridges
2016-08-25
Theses
Electronic Resource
English
DDC: | 629 |
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