This paper aims to present and analyze the results of an ongoing research project on the use of NSM and side-NSM-FRP composites for the purpose of increasing the load-carrying capacity of two-pan continuous RC beams. This research study comprises two parts; an experimental part and a finite element (FE) part. First, three large-scale two-span beams were statically investigated; one control beam and two other beams initially strengthened in bending with two 6 mm diameter CFRP bars. Second, a three dimensional (3D) FE model was developed, using the computer software ABAQUS, in order to predict the flexural performance of the tested beams and to investigate the influence of the models applied to the CFRP-resin-concrete interfaces. The results obtained indicated that the side-NSM-CFRP bars system is a convenient alternative to the conventional one for strengthening continuous beams. For some strengthening configurations, the side-NSM technique proved to be more efficient than the NSM technique, particularly when the CFRP bars were applied solely in the hogging region or the sagging regions. The moment redistribution of strengthened beams was negatively affected when the steel reinforcement ratio in the hogging region was increased. Nevertheless, the moment redistribution degree was significantly affected by the position and arrangement of the CFRP bars. The 3D-FE analysis developed with the cohesive zone model can capture the main aspects observed from the experiments. •The NSM and side-NSM techniques could be used to improve the load-carrying capacity of the continuous RC beams.•The side-NSM-CFRP system is a convenient alternative to the NSM system for strengthening continuous beams.•The moment redistribution degree of NSM/side-NSM CFRP beams is affected by the position and arrangement of the CFRP bars.•The 3D FE analysis developed with the CZM can capture the main aspects observed from the experiments.