Numerical analyses of the connections between representative SFRC prestressed rings of off-shore wind towers

Abstract

Off-shore wind towers are the wind farms used to harvest wind energy to generate electricity on water bodies. With the growing need of sustainable production for electricity, off shore wind towers are finding a rapid growth in application. In fact, 4% of European electricity demands will be generated by offshore wind towers by 2020 in European waters. The current project concentrates on development of an innovative structural system using advanced materials for lightweight and durable offshore towers. The present paper discusses the nonlinear finite element modelling of the connections between representative prefabricated rings of off-shore wind towers made by steel fibre reinforced concrete (SFRC) and prestressed by a hybrid system formed by carbon fibre reinforced polymers (CFRP) bars and steel strands. The connection between these two rings are assured by post-tension high steel strength cables and concrete-concrete shear friction of treated surfaces. The model takes into account different types of loads and moments originating from rotor, wind and water currents considering the critical loading conditions. The material nonlinear analyses were carried out inFEMIX V4.0 software, considering a 3D constitutive model capable of simulating the relevant nonlinear features of the SFRC, and interface finite elements for modelling the shear friction of the concrete-concrete surfaces in contact. The SFRC rings are modelled by solid elements, and the longitudinal CFRP bars and steel strands by 3D embedded cables. Parametric studies are carried out in order to assess the influence of different fracture parameters of the SFRC and post-tension level in the cables (steel and CFRP) on the performance of the connection between the two rings.