Implementation of a 6-dof hypoplastic macroelement in a finite element code

The macroelement concept, introduced for the first time by Nova & Montrasio (1991) is particularly well suited for complex soil–foundation–superstructure interaction (SFSI) problems of special structures such as tall bridge piers, towers or wind turbines under severe loading conditions. The capability of some of the models proposed in the literature to simulate the foundation response under six-dimensional loading paths (Bienen et al. 2006; Salciarini et al. 2011) is of great importance in the analysis of offshore structures such as mobile jack-up drilling units. In this work, the numerical implementation of the 6–dof hypoplastic macroelement proposed by Salciarini et al. (2011) in the Finite Element code Abaqus is presented. Particular attention has been paid to the development of a robust, accurate and efficient algorithm for the integration of the inelastic and incrementally non–linear constitutive equations of the macroelement. In this respect, an explicit adaptive integration algorithm with error control, based on the application of two embedded Runge–Kutta schemes of 2nd and 3rd order has been considered the most suitable candidate. The macroelement implementation has then be used to analyze the response to wind loading of a wind turbine. The results obtained from a series of cyclic and monotonic simulations demonstrate the computational efficiency of the proposed approach and the importance of the coupling effects between the different degrees of freedom of the foundation.