Nonlinear Stability of Sandwich Functionally Graded Cylindrical Shells with Stiffeners Under Axial Compression in Thermal Environment

The geometrically nonlinear response of sandwich functionally graded cylindrical shells reinforced by orthogonal and/or spiral stiffeners and subjected to axial compressive loads is investigated in this paper. Two types of sandwich functionally graded material models are considered. The formulations are based on the Donnell shell theory considering geometrical nonlinearity and Pasternak’s elastic foundation. The improved Lekhnitskii’s smeared stiffener technique is used to account for the stiffener effects with both mechanical and thermal stresses. The results obtained indicate that the spiral stiffeners have significantly beneficial influences in comparison with orthogonal stiffeners on the nonlinear buckling behavior of shells. The relatively large effects of temperature change, geometrical and material parameters are also demonstrated in the numerical investigations.

Dynamic Analysis of Wind Turbine Tower-Foundation with Stiffeners

In the light of the geometric characteristics of wind turbine and the distribution of stiffeners, the finite element models for the megawatt horizontal axis wind turbine are established by ANSYS. A model analysis is made of the effect of the foundation stiffness, longitudinal stiffeners, ring stiffeners and orthogonal stiffeners on natural frequency and vibration mode of the tower. The results show that the foundation stiffness and stiffeners all have a certain influence on the natural frequency of the tower. There is a 7% difference in the first-order natural frequency between the models of the tower with and without foundation stiffness; there is an increase in natural frequency of the tower when longitudinal stiffeners or orthogonal stiffeners are considered, while natural frequency of the tower experiences an erratic change with the increase of ring stiffeners. The present study will provide some theoretical basis for the optimization design of wind turbines.