On the elasto-plastic behavior of continuous steel beams reinforced by bonded CFRP lamina

This paper is focused on the flexural behavior of steel beams reinforced with carbon fibers reinforced polymer materials (CFRPs). In order to fully exploit the potentialities of a CFRP reinforcement the beam has to be designed in the plastic regime. In fact in the linear elastic case the contribution of a thin CFRP lamina attached on the tension side are very limited both for the ultimate and serviceability limit states. However debonding of the CFRP lamina or failure of the carbon reinforcement may prevent the achievement of the full plastic flexural capacity of the section. Non-linear finite element models have been employed to compute the elasto-plastic response of the structure in terms of internal forces and stresses; however these models are often complicated, time consuming and not available for practitioners. In the present paper we propose a simple approach to compute the response of the reinforced beam up to the ultimate limit state, which can be easily implemented and exploited for design purposes. This method has been validated against results from literature and from ad hoc formulated finite element models and then adopted to study a continuous beam over three supports. Parametric studies have been performed in order to point out the influence on the main design reinforcement parameters on the elasto-plastic response of the reinforced steel beam.