POLIMI-CIRIVE
Overview of the politecnico di Milano Wind Tunnel
Bridges and Boats and Planes… And So Much More The Politecnico di Milano Wind Tunnel is unusual in that it has two different test sections in the closedcircuit loop. This arrangement provides the ability to test in many different fields, applications and industries. prof. Giorgio Diana, of Politecnico di Milano describes the facility
t
he poLitecnico di Milano Wind Tunnel (GVPM)
has been operating since 2001 and is located on the academic campus of the Politecnico di Milano university. Thus the GVPM has a dual aim, being both a purely research tool and, secondly, a modern instrument for high-technology industrial applications, offering advantageous reciprocal synergies. A peculiar characteristic of the facility is the closed circuit arrangement with two different test sections in the loop. The Boundary Layer Test Section (section 14 m x 4 m, length 35 m, maximum wind velocity of 16 m/s and turbulence index <2 percent) enables the setting up of upstream active or passive turbulence generators to simulate the atmospheric boundary layer (turbulence index higher than 25 percent). The high-speed low-turbulence test section (4 m wide, 3.84 m high, and 6 m long) facilitates tests in a closed test section and in an open jet. The maximum wind velocity is 55 m/s and the turbulence level is less than 0.1 percent. Thanks to these capabilities the facility can operate in a wide range of research fields in aerodynamics, including: suspension bridges, buildings, sailing boats (America’s Cup class), high-speed trains, vehicles, aircrafts, helicopters, sport aerodynamics and wind energy. 82
LONG SpAN BRiDGES AERODYNAMiCS Bridges are subjected to static and dynamic loads due to the incoming wind. A bridge with a main span longer than 500 m is generally defined a long bridge. If over 1000-1500 m it is considered a very long span bridge. Very long span bridges are generally, up to now, suspension bridges while smaller ones (500-1000 m) are generally cable stayed and those below 500 m bridges can be of any type including steel lattice structures. With regard to long span bridges, wind effects are a major problem to be considered for the stability of the structure. Politecnico di Milano’s Research Centre for Wind Engineering (CIRIVE) gained experience in bridges aerodynamic because of the studies carried out on the project of the Messina Strait Bridge that, with its length of 3300 m, when completed, will stand undisputed as the world’s longest single span bridge. For this purpose state of the art test rigs were designed in order to perform tests on both full bridge aeroelastic models and sectional ones. Considering the aerodynamic of the bridge, the deck is most sensitive part to the wind action: sectional models permit complete experimental aerodynamic characterization of the deck section. Steady state coefficients, flutter derivatives and aerodynamic admittance functions WIND TUNNEL INTERNATIONAL | 2010