On the Investigation of the Most Critical Shape Imperfections for Wind Turbine Tower Shell Structures

As the wind power industry is the fastest growing energy resource in the world, wind turbine structures have been continuously increasing their dimensions and in particular their height, a trend which is expected to continue in the future. The height of wind turbines has doubled during the last 10 years and their power has increased by a factor of 5. This increase in height comes along with an overwhelming increase in the construction cost as well as with a plethora of emerging problems involving design/construction/erection processes. The present paper studies the problem of the most critical geometrical imperfections for the buckling capacity of wind turbine tower shell structures. The presented study is applied to many different tower geometries and includes linear elastic as well as plastic buckling through a series of nonlinear finite element calculations. The most critical geometrical shape imperfection is calculated through the parametric interaction of the buckling modes of the shell tower structure. The results present the sensitivity of the buckling capacity of the shell structure to the interaction of the modes considered as the geometrical onset for the nonlinear finite element analysis. The produced interactions are compared to the widely applied Eurocode design codes and useful conclusions are drawn.

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