Sandwich metal foam rings for wind turbine tower buckling enhancment

In this paper, buckling analysis of wind energy towers is performed. Stiffening rings are used in various heights to enhance the dynamic behaviour of wind energy structures, making the tower stiffer and reducing the susceptibility of the structure to local buckling under external loads. The augmenting stiffening rings may be steel solid or composite, the latter being a sandwich steel ring filled with metal foam, either vertical or horizontal sandwich rings. This design approach aims to take advantage of the low density of the metal to achieve stiffening with a reduced bill of materials, whilst the porosity of the foam presents additional opportunities to control structural damping. Three different design configurations are considered to assess the buckling characteristics of the proposed approach: one unstiffened tower, one stiffened tower through solid steel rings, a stiffened tower with horizontal sandwich metal foam ring, and a stiffened tower with vertical sandwich metal foam rings. Both linear and nonlinear buckling resistance were studied to evaluate the influence of sandwich rings. All stiffening schemes were compared in terms of bucklingimprovement and mass increase, whereas the impact on the structure's modal properties is assessed.