Mechanical behavior of prestressed UHPC wind turbine tower columns under combined axial compression and bending

Abstract

Developing offshore wind power can effectively reduce carbon emissions, and adopting large‐capacity wind turbines is an important way to achieve cost reduction and efficiency increase. With increasing power capacity, the hub height and rotor‐nacelle assemblies (RNA) load will increase significantly. Ultra‐high performance concrete (UHPC) possesses ultra‐high compressive performance, good tensile, fatigue, and corrosion resistance, and thus is an effective way to further improve the mechanical performance and economic efficiency of tall offshore wind turbine (OWT) towers. Evaluation of ultimate strength is an essential aspect of design for OWT towers, and the tower structure is mainly under the combined action of axial compression from the self‐weight and RNA loads and bending from the eccentricities of RNA and aerodynamic loads from the rotor on the tower top. In this work, the mechanical behavior of prestressed UHPC wind turbine tower columns under combined axial compression and bending was numerically investigated. The finite element (FE) analyses were carried out using ABAQUS, and the material and geometric nonlinearity were considered in the model, as well as the tensile strain hardening properties of UHPC. The FE models were firstly verified by the typical experimental results of UHPC hollow columns, reinforced UHPC beams, prestressed UHPC beams, and prestressed concrete‐steel hybrid wind turbine tower model. Then the parametric study was carried out, and the parameters included the control stress and number of prestressing tendons, rib number, diameter‐to‐thickness ratio of the UHPC column, steel ratio of longitudinal reinforcement, axial load ratio, and UHPC strength. The calculation methods for flexural capacity of prestressed UHPC wind turbine tower columns were finally proposed, and were found to agree well with the modeling results.