A gas turbine engine including a gas exhaust duct assembly which comprises an annular shroud forming at least a section of an inner wall of a gas exhaust duct, a plurality of strut members radially projecting from the shroud, and a plurality of insert members. The strut members are disposed in a circumferentially, substantially equally spaced-apart relationship, and extend in a substantially axial direction. The insert members each define a circumferential section of an outer wall of the gas exhaust duct and are positioned in a space between adjacent strut members, and are secured to same. The gas exhaust duct is thereby defined between inner surfaces of the insert members and the outer surface of the shroud, and is circumferentially divided by the respective strut members, for directing exhaust gases rearwardly in an axial direction, meanwhile surrounding flow passages are defined by outer surfaces of the insert members and the strut members in combination, for directing surrounding air flows rearwardly in an axial, radial and inward direction.