Aerodynanmic and aeroelastic response of large structures: historical review and some recent results

A general overview on the dynamic analysis of structures under turbulent wind is presented. The attention focuses here on three groups of structures: large roofs, tall buildings and long-span bridges. The experimental tests carried out in the boundary-layer wind tunnel for the design of the large roofs of the new Olympic stadium (Karaiskaki) in Pyraeus (Greece), Manfredonia (Italy) and “Delle Alpi” of Turin (Italy) are presented. Some time-domain dynamic response analyses performed on the Karaiskaki and the Olympic stadium in Rome are also given. The peculiar shape and the location of these roofs let arise the question about the actual distribution of the wind loads. The data recorded in the wind tunnel are used for the numerical dynamic simulation in the time domain. The full-scale correlation of wind pressures is considered. The final aim is the definition of the design loads of the steel lattice structures. Among the tall buildings which are presently under construction in Italy, CRIACIV has investigated two particularly interesting cases: the directional centre tower UNIPOL on via Larga in Bologna, and the principal tower of the new centre of P.za Garibaldi-Repubblica in Milano. The main targets of the research are the evaluation of the wind actions from both global and local point of view. The investigation includes: the assessment of the components of the global forces at the foundation through an aerodynamic balance; the measurement of the local pressures; a statistical analysis of the pressure time-history, the evaluation of maximum local effects and global effect through the integration of the local pressures. Other tests consider the circulation of air around the building and are used for different purposes. Finally, some results in the simulation of the response of long-span bridge under turbulent wind will be presented. The techniques adopted are based on the finite element simulation of the bridge and semi-empirical wind load models, which are based on experimental coefficients measured in the wind tunnel. A short overview of the numerical techniques required for the analysis is provided, including the generation of multi-correlated wind fields through autoregressive filters, the numerical identification of time-domain unsteady quantities, the solution of the aeroelastic stability problem (flutter analysis) in the frequency- and time-domain, and the transient analysis under turbulent flow.