New proposal for flexural strengthening of a continuous I-steel beam using FRP laminate under thermo-mechanical loading

Construction materials such as composites are used recently for the reinforcement and rehabilitation of structures subject to risks of partial or total degradation during their service, which are due to either poor design, overload or a charge assignment. The use of fibers is a new technique which gives additional rigidity and resistance to structures. In this research, we develop an approach which makes it possible to analyze the interfacial constraints which are the cause of the delamination phenomenon at the level of the structure, for a continuous steel beam bonded by a FRP laminate plate, under thermo-mechanical loading coupled with the shear lag model. In such plated beams, shear forces develop in the bonded beam and these will be transferred to the FRP plate via the adhesion technique. Thus, the interfacial shear stress and normal stress will develop consequently, and debonding may occur at the FRP plate ends due to high interfacial stress values in this area. This original research aims to study the debonding phenomenon using an analytical model, in order to identify the interfacial stresses of a continuous steel beam strengthened by the FRP plate with taper model, taking into account a new coupled approach of thermomechanical loading effect. Finally, numerical comparisons between the existing solutions and the present solution enable a clear appreciation of the effects of various parameters. This article explores the effects of various parameters related to the subject, such as the effect of thermal loading, geometrical and physical properties, on the stress behavior of FRP composites. This solution is intended for application to beams made of all kinds of materials bonded with a thin composite plate. For steel I-beam section, a geometrical coefficient q is determined to show the effect of the adherend shear deformations. This research is helpful for the understanding on mechanical behaviour of the interface and design of such structures.