Comportamento aeroelastico di un cilindro rettangolare 3:2

This paper reports some results of static and dynamic wind tunnel tests on a rectangular cylinder with a side ratio of 3:2, with the short side transverse to the flow. A significant negative value of the galloping stability parameter, obtained from static tests, showed that the quasi-steady galloping critical wind speed can be close to or even below that of vortex-shedding resonance for values of the Scruton number which can be found in many structures of practical interest. The instability of the section is due to the interaction between vortex-induced vibrations and galloping, and considerably large vertical oscillations were observed, also for low reduced wind speed and high values of the Scruton number. The two phenomena occurred separately only for a ratio of galloping to vortex-shedding resonance wind speed around 7. This limit value of the ratio is strongly underestimated by the Eurocode and the Italian CNR recommendations. Also the values obtained for both the galloping stability parameter and the Strouhal number are not in agreement with those reported in European and Italian recommendations, which do not seem conservative for design purposes.