On the nonlinear dynamic analysis of annular baffled steel containers isolated by bearings

Abstract

This paper focuses on numerically scrutinizing the simultaneous influences of the base-isolator devices and annular baffles on the dynamic behavior of a three-dimensional (3D) cylindrical water storage tank, considering anirrotationaland inviscidfluidundergoing smallvibrations. A coupled acoustic-structure finite element formulationis developed for the analysis of the nonlinear dynamic behavior of the thin-walleddeformable cylindrical tanksunder real ground excitations. The established FEM procedure is competent in assaying the precise three-dimensional behavior of the isolated ground-supported annular baffled containers, including the performance of laminated rubber-bearing isolation devices in frequency and time domains. Vibration characteristics of water sloshing inside the benchmark tank are investigated under five different earthquakes with long and short-period contents. Furthermore, the dynamic response components of the base shear force, base moment, hydrodynamic pressure, and bearing deformation of the isolation devices regarding some system parameters comprising lateral isolation and locations of baffle devices are quantified efficaciously. In conclusion, the numerical simulations in the time-domain revealed that satisfactory performance of the baffled liquid tanks might not be achieved by only relying on the first convective mode frequency of the tanks due to an unwanted increase of sloshing amplitudes in exceptional cases of liquid tank geometry and baffles; the baffles with smaller effects on the first convective modes were more effective on decreasing the sloshing wave amplitudes. Hence, in the case of slender tanks, it is recommended that a baffle geometry be selected for each earthquake frequency content and analyzed over time to obtain the best performance from the baffles, but for the broad tanks, a baffle selection independent of the earthquake frequency content might be acceptable. Also, the results indicate that in the board tanks, top-mounted baffles amplify the seismic response of the system; thus, remarkable attention would be required in using baffles in such tanks; therefore, it has been recommended to use mid-mounted baffles in these tanks.