Finite element modelling of the contact between shell structure and foundation

Abstract

This paper presents the problem of modelling of a shell structure as a vertical steel tank with a volume of 20000 cubic meters under a combination of static loads. The total height of the cylindrical wall of the tank is 17880 mm, and its diameter is 39900 mm. The wall thicknesses have been determined according to the design requirements of strength and buckling. The geometric model of the object has an axisymmetric form. The task is to perform the analysis of the stress-deformed state of the cylindrical wall and the contact zone of the wall with the foundation under different loads. The type of the contact is "Frictional" with a coefficient of friction equal to 0.45. The lower part of the foundation has been fixed. We have also restricted the radial movement of the upper part of the tank. Modelling has been carried out using the ANSYS simulation software. In three-dimensional modelling, finite elements of the SHELL281 type have been used. When solving an axisymmetric problem in a two-dimensional formulation, we have used PLANE183 finite elements. We have verified the model by comparing the radial displacements of the shell obtained using numerical simulation with the values calculated analytically. The discrepancy between the data does not exceed 5%, which indicates the adequacy of the finite element model. We have performed the analysis for non-standard operating conditions, which suppose the excessive internal pressure in the tank (2.5 and 3 kPa against 2 kPa under normal conditions). The contact "bottom - foundation" with a one-way connection allows separation of the bottom from the foundation. The complete detachment occurs under a specific combination of excessive and hydrostatic pressures. For certain levels of liquid in the tank, the gap decreases almost to zero, followed by a noticeable increase. This rapid change can be explained by the fact that with an increase in the hydrostatic pressure the effect of separation due to the excessive pressure decreases, and then the process of internal separation occurs, caused by the increasing moment from hydrostatic pressure.