Connection assembly between two structures (130, 150), the connection assembly comprising: - a generally cylindrical or frustoconical insert which has a bore and which is arranged in order to bring about a connection with one of the two structures using a fixing element (160, 161) which comprises a rod which is inserted in the bore, the longitudinal axis of the bore being different from the longitudinal axis of the insert so that the insert is generally in the form of an eccentric ring, - a generally cylindrical or frustoconical eccentric ring which is made of deformable material and which is arranged to be accommodated in a through-opening of the other structure of the two structures (130, 150), the through-opening of the structure having a shape which complements the external surface generated by revolution of the eccentric ring, the eccentric ring further comprising a through-opening which has a shape which complements the external surface generated by revolution of the insert and which is arranged to accommodate the insert therein, the longitudinal axis of the through-opening of the eccentric ring being aligned or substantially aligned with the longitudinal axis of the insert and the eccentric ring being fitted on the insert so that the assembly of the insert and the eccentric ring constitutes a "double eccentric" fitting in which the eccentric ring is fitted on the insert, which is itself in the form of an eccentric ring, and - two compression elements (140, 142) which extend radially with respect to the longitudinal axis of the through-opening and which each have a through-hole which is configured for the passage of the fixing element (160, 161) and which is, on the one hand, fixedly joined to the other structure or which has an abutment surface with respect to a surface of the other structure, which is perpendicular to the longitudinal axis of the through-opening and which has, on the other hand, an abutment surface with respect to at least one surface of the insert, perpendicular to the longitudinal axis of the through-opening, the eccentric ring being sized to have a compressed shape when the two compression elements (140, 142) are fixed in an abutment position with respect to the abutment surfaces. - a generally cylindrical or frustoconical insert which has a bore and which is arranged in order to bring about a connection with one of the two structures using a fixing element (160, 161) which comprises a rod which is inserted in the bore, the longitudinal axis of the bore being different from the longitudinal axis of the insert so that the insert is generally in the form of an eccentric ring, - a generally cylindrical or frustoconical eccentric ring which is made of deformable material and which is arranged to be accommodated in a through-opening of the other structure of the two structures (130, 150), the through-opening of the structure having a shape which complements the external surface generated by revolution of the eccentric ring, the eccentric ring further comprising a through-opening which has a shape which complements the external surface generated by revolution of the insert and which is arranged to accommodate the insert therein, the longitudinal axis of the through-opening of the eccentric ring being aligned or substantially aligned with the longitudinal axis of the insert and the eccentric ring being fitted on the insert so that the assembly of the insert and the eccentric ring constitutes a "double eccentric" fitting in which the eccentric ring is fitted on the insert, which is itself in the form of an eccentric ring, and - two compression elements (140, 142) which extend radially with respect to the longitudinal axis of the through-opening and which each have a through-hole which is configured for the passage of the fixing element (160, 161) and which is, on the one hand, fixedly joined to the other structure or which has an abutment surface with respect to a surface of the other structure, which is perpendicular to the longitudinal axis of the through-opening and which has, on the other hand, an abutment surface with respect to at least one surface of the insert, perpendicular to the longitudinal axis of the through-opening, the eccentric ring being sized to have a compressed shape when the two compression elements (140, 142) are fixed in an abutment position with respect to the abutment surfaces.