Finite element formulations for implicit beam-to-solid coupling: numerical obstacles and solution strategies

Due to their exceptional ability to simplify the finite element analysis of complex geotechnical problems involving a high number of slender structures, embedded beam formulations representing implicit beam-to-solid finite elements have attracted widespread interest from the scientific community. While numerous scientific contributions confirm their suitability for the modelling of pile-type structures in the light of load-settlement analyses, insight to the numerical phenomenon of oscillations traditionally occurring in the predicted skin traction profiles is rare. This numerical obstacle is the core of the present work, in
which we perform parametric studies to investigate selected features of the recently developed embedded beam element with interaction surface, an improved version of the well-known embedded beam element with interaction line employed in the FE code Plaxis 3D. The results provide numerical evidence on the cause of the oscillatory nature, and shed light on potential solution strategies; moreover, they provide guidance with respect to future lines of research to achieve more genuine solutions.