If I understand the question correctly, I believe many times these buildings rely on an upper ‘gable rafter set’, supported by the upper purlin plate, and a ‘lower shed rafter set’, supported by the upper and lower plates. In this case the upper tie beam, which is carrying the upper gable rafter set thrust or tension, is just that a tie beam and I believe a necessary element of the frame. I have built a number of building using an upper queen post/tie beam system and believe the tie beams are a required element. I’ve seen this style of building w/o the upper tie beam, but they will have common coller ties for the common rafters at the upper plate location. I also like the braces to the upper tie beam as they stiffen the roof system in the transverse direction.
Pete
