In the past three decades, one-dimensional (1D) thermal model was usually used to estimate the thermal responses of glass fiber-reinforced polymer (GFRP) materials and structures. However, the temperature gradient and mechanical degradation of whole cross sections cannot be accurately evaluated. To address this issue, a two-dimensional (2D) thermomechanical model was developed to predict the thermal and mechanical responses of rectangular GFRP tubes subjected to one-side ISO-834 fire exposure in this paper. The 2D governing heat transfer equations with thermal boundary conditions, discretized by alternating direction implicit (ADI) method, were solved by Gauss-Seidel iterative approach. Then the temperature-dependent mechanical responses were obtained by considering the elastic modulus degradation from glass transition and decomposition of resin. The temperatures and midspan deflections of available experimental results can be reasonably predicted. The overestimation of deflections could be attributed to the underestimation of bending stiffness. This model can also be extended to simulate the thermomechanical responses of beams and columns subjected to multiside fire loading, which may occur in real fire scenarios.

Composite sandwich materials with glass fibre-reinforced plastic (GFRP) skins and a foam core have been widely used in civil engineering. However, the interfacial delamination is the main failure mode in practice, especially at elevated temperatures. Temperature-induced interfacial shear stress can be generated because of the different coefficients of thermal expansion of GFRP skin and foam core, which can weaken the interfacial bond strength of sandwich materials. In this study, to investigate the distribution of temperature-induced interfacial strain, an analytical model was developed by using the infinitesimal method. In the meantime, a series of foam-core composite sandwich materials were tested via a kind of non-direct test method at different temperatures to validate the accuracy of the proposed analytical model. Finally, the comparison between experimental and analytical results demonstrates that the proposed analytical model can predict the interfacial strain distribution of sandwich structures at elevated temperatures.