GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 2.3 255 where H is the design height of the fluid, R is the radius of the tank, s is the equivalent uniform thickness of the wall of the tank, ρ the density of the liquid mass and E the modulus of elasticity of the material. The coefficients Ci and Cc are obtained from an exact model of the tank-liquid system and included into Appendix 1 in Eurocode 8. Ci is a non-dimensional coefficient, while Cc is expressed in s/m 1/2 . The ���� ��������� �� ��� ������� ��������� ���� ��������� �� ��� ��� ���� ��� �� ���������� main objective of the ���� ��������� �� ��� ��� ���� ambient vibration test performed on the oil tank ��� �� ���������� was to understand if it was possible to measure the impulsive and convective periods instead of calculating them. The structure tested is a vertical cylindrical steel structure, with a radius of 13.72 m and 17 m height, 10.000 m 3 capacity. At the time the tests were done the tank was almost empty, since it is a buffer tank. Therefore, the same test has been taken also on a slightly smaller water tank that was, instead, full. The results are shown in Fig. 2 and in Tab. 1 a comparison between the theoretical and experimental periods is presented (��������� Massolino et al. , 2014)� ��� ������ ���������� ��� ��� ��� . The period calculated for the oil tank almost empty are approximated, since the Eurocode 8 code does not provide formulations for a filling ratio lower than 0.3. The results are promising even if not totally satisfactory, probably because of a bad coupling between the sensors and the structure. More tests should be performed on many other tanks so to verify if these considerations are reliable. Fig. 2 – a) Results of H/H ratio for the oil tank, almost empty (less than 3 meters of fluid level); b) results of H/H ratio for the water tank, completely filled up. Tab. 1 - Comparison between convective and impulsive periods obtained by experimental vibration tests and by theoretical formulations. T imp T conv f imp f conv Exp.f imp Exp.f conv [s] [s] [Hz] [Hz] [Hz] [Hz] Water tank (full) 0.20 4.9 4.97 0.20 4 <0.3 Oil tank (full) 0.24-0.26 5.59 3.85-4.14 0.18 / / [Oil tank (empty)] ≈ 0.05 ≈ 8.47 ≈ 19 ≈ 0.12 ≈ 10 <0.3 Hangar. NoiseInputModalAnalysistechniquehaswidelybeenadoptedforthecharacterization of standard buildings, giving reliable results especially for multi-storeyed ones with regular characteristics in height and plan architecture. In this study, ambient vibration surveys have been implemented on a two-storeys hangar of 60x30 m planar dimension, framework structure with prestressed reinforced concrete pillars and reinforced masonry infill walls. The two floors has different height: 6 and 3 m respectively. The stairs are always considered as an element of major stiffness, so when they are located on one side, as in this case, the building shows a stiffness planar asymmetry. Therefore, a strong torsional component is expected. In order to