Ultra High Bi-pass Ratio Engines constitute one of the most cutting-edge architectures in propulsion research panorama. Fundamentally, their introduction is motivated by the need of reducing fuel consumptions. Most of research projects on this topic focus on solving the numerous aerodynamic, control and structural challenges deriving from concepts. In this work, structural issues will constitute the central focus. The present study is the result of a 6-month internship in Airbus Operations SAS (Toulouse, France). The project aims to explore possible solutions of the design of the airframe of such engines. For this purpose, Topology Optimization (TO) is adopted as main tool: it allows to find the optimal arrangement of masses in pre-sizing phases.