The heightening use of thin-walled steel structures necessitates the search for fast and efficient methods of their reinforcement. One solution might be the application of bonded composite tapes. The author of the work has conducted a number of studies so far, which showed a beneficial effect of the use of bonded composite tapes to limit displacements and strains of bent thin-walled sigma beams. In practice, thin-walled steel beams of sigma section are most commonly used as purlins in steel halls, where they cooperate with the sandwich panel. To approach this issue, the present work describes pilot studies in which the effect of the use of composite tapes on the operation of bent thin-walled beams connected with a sandwich panel was analyzed. A four-point bending test was conducted on 9 thin-walled sigma beams Σ200x70x2, 3 meters long, connected with a 6 cm thick PIRTECH sandwich panel. Three samples were treated as reference, the next three were reinforced by bonding a composite tape to the lower flange of the steel beam, and the last three were reinforced by bonding a tape to the web. The conducted studies indicate that the adhesion of composite tapes to the lower flange of the thin-walled sigma beam cooperating with the sandwich panel allows for a significant reduction in beam strains and vertical displacements.