Steel reinforced polymer (SRP) and steel reinforced grout (SRG) systems have emerged as viable and cost-effective solutions for the flexural strengthening of RC beams/slabs. Experimental tests recently performed at the University of Salerno have allowed for verifying the satisfactory behaviour exhibited by RC slabs strengthened in bending by SRG/SRP systems, both in terms of strength and deformability. Based on the results of this experimental campaign, a simple and efficient OpenSees model is presented herein with the twofold objective of: (1) simulating the behavior of shallow RC beams flexurally strengthened with SRG/SRP; (2) calibrating a constitutive law of the SRG/SRP-concrete interface based on the local deformation tensor evaluated. The preliminary comparison between experimental results and numerical predictions have allowed for verifying the accuracy of the developed model.