An analytical investigation of the buckling/wrinkling behavior of GFRP webs in cell-core sandwiches subjected to combined in-plane shear and bending stresses is conducted. Web-core panels are modeled as long orthotropic plates stabilized by a relatively thick layer of elastic foam. The boundary condition of the plate is defined according to the interaction between the webs and face sheets in the presence of the core material by applying a series of numerical analyses using the three-dimensional finite element modeling. Two approaches are adopted to predict the wrinkling behavior. The first is to predict the buckling/wrinkling of webs subjected to combined shear and bending loads using a mixed-mode interaction formula. In the second approach, the wrinkling behavior of web-core panels is treated as a biaxial compression-tension local buckling problem. The developed approaches are applied to predict the wrinkling loads of thin-walled webs in GFRP cell-core sandwich beams designed for the GFRP cell-core sandwich roof of the Novartis Campus Main Gate Building constructed in Switzerland. (C) 2012 Elsevier Ltd. All rights reserved.