Performance of an innovative fully-assembled dense ribs foundation for wind turbines under combined loads

With the ongoing development of wind turbines (WTs) towards larger geometrical sizes and higher capacities, foundations with good mechanical properties under combined loads have become a critical prerequisite for the safe operation of WTs. Therefore, this study first innovatively develops a fully-assembled dense ribs wind turbine foundation, yielding good mechanical performance. Then, an innovative pulley block constant-pressure device and a novel regional counterweight loading system are proposed, achieving accurate simulation of combined loads in scaled experiments. Subsequently, experimental tests and numerical verifications are implemented to clarify the advantages of the dense ribs configuration. Finally, significant improvements in foundation mechanical performance are presented: (a) Rib beam stresses increase approximately linearly with load magnitude and exhibit spatial dependence on proximity to the wind direction, with stress concentrations near the pedestal pillar, thus necessitating chamfered rib designs. (b) Strategies of connection and non-connection setup among the base plates were simultaneously examined by scaled model and FEM approaches, highlighting the practicality and simplicity of the latter in fully-assembled dense ribs foundations. The soil pressure distribution at the foundation base, without connections between base plates, is discontinuous and wavelike (experimental and numerical deviation<8%). Moreover, the absence of base plate connections reduces the bending moment at the middle of the base plate by 10-40%, bending-moment reduction occurs at the mid-plate, without significant edge amplification. (c) A comprehensive comparison with existing single rib layout is also conducted, and the results reinforce its reliability and effectiveness of dense ribs configuration, which enhances the uniformity of load transfer, reduces foundation soil pressure by 37%, and extends the pressure dispersion angle to 120°, thereby mitigating localized stress risks.