A method for assembling two structural elements, at least one of the two structural elements being tube-shaped and including a skin made of a fiber-reinforced composite material. The ability of the element to adapt to the shape and perimeter of a junction interface is improved by providing longitudinal grooves distributed on the circumference of the junction interface. The grooves are of a sufficient length to provide the junction interface with the flexibility to accommodate, through relative radial movement of each portion located between two grooves, differences in shape and perimeter among the junction interfaces of the two structural elements.