The buckling behavior of annular sector plates can be an essential design criterion due to their wide range of applications in various industries. The first and third shear defor- mation theories have been previously applied to formulate thick annular sector plates. In these theories, five unknown parameters generally appear in the coupled Partial Differ- ential Equations (PDEs), which are reduced to three due to a symmetrical configuration of the plates. This reduction can also be improved to two coupled PDEs utilizing the Refined Plate Theory (RPT) in a symmetrical construction. In this study, the RPT is separately used through five shear deformation functions to develop the coupled PDEs, which describe the buckling behavior of isotropic thick annular sector plates. Applying the Generalized Integral Transforms Technique (GITT), the PDEs are directly converted to infinite linear algebraic equations. This approach is based on twelve boundary con- ditions, which are achieved by combining simply supported and/or clamped edges as well as in-plane radial and tangential loads. Finally, the procedure generates an eigen- value problem from which the buckling coefficient is calculated. The results show that the type of shear deformation functions does not affect the buckling coefficient despite the fact that the proposed functions come in a variety of mathematical forms, such as polynomial, exponential, trigonometric, and hyperbolic. Three dimensionless geometrical parameters, including the thickness-to-outer radius ratio, the inner-to-outer radius ratio, and the central angle, affect the buckling coefficient values. Increasing the first, second, and third parameters without variation in the others leads to the buckling coefficient decreasing in cubic curve trends, increasing in approximate exponential curve trends, and decreasing in homographic curve trends for most boundary conditions, respectively.
