This thesis discusses the effect of wind on air supported structures and methods of wind tunnel testing and analysis that can be used for design. Two design approaches are considered. Firstly the measurement of pressures on a rigid model in a wind tunnel followed by a separate structural analysis and secondly flexible aeroelastic model testing which combines the functions of wind tunnel and structural models. In order to compare these two procedures a number of rigid and aeroelastic models were tested in a wind tunnel and the displacements of a full scale structure under wind load were measured. It was found that analysis of the fluctuating pressures on the rigid model predicted certain types of dynamic response of the flexible models and full scale structure, but that there is always the danger of some aeroelastic instability, especially at low inflation pressures, which cannot be predicted by rigid model tests. With present knowledge it is not possible to undertake a dynamic analysis of an air supported structure which includes all the aeroelastic terms which may be important. However a method is presented which at least enables the natural frequencies and mode shapes of membrane structures to be calculated, including the effects of the air moving with the structure under zero wind conditions. It is concluded that properly designed air supported structures are well able to resist wind loads and this is confirmed by experience with full scale structures. However, as inflation pressures are reduced in the interests of structural and inflation system economy, there will be a point where unacceptable deflections take place and this area of behaviour can only be examined using flexible aeroelastic models.
|Date of Award||1983|