The object of research is a section of a fiberglass pipe of a metallurgical enterprise's flue on sliding supports, working according to a split scheme. The material of the flue is fiberglass with mineral wool filler. The purpose of this work is to analyze the deflections of a three-layer cylindrical shell made of polymer composites under complex thermomechanical action and compare the results of full-scale and numerical experiments. The calculation considers the load from the own weight of the structure and the additional load. The range of gas operating temperatures from 22 to 130 °C is considered. Method. Numerical calculation is performed in the ANSYS Workbench software package (ansys.com). For finite element analysis of the shell under thermomechanical action, a bundle of Static Thermal and Static Structural modules is used. Results. The deflections of the shell are evaluated; the results of full-scale tests and the simulation of the experiment are compared.