Flexural performance of NSM and PNSM beams maintaining the ACI440 bar diameter to groove size limitation

• The flexural performance of NSM and PNSM-strengthened beams was investigated. • Providing design guidelines covering the full behavior for BFRP and GFRP beams. • The effect of the groove size-to-rebar diameter was examined. • Different prestressing levels and groove numbers were studied. • Propose mathematical relationships depending on the material properties. • Compare results with ACI440 and the proposed relationships. In this study, the flexural behavior of RC beams upon the strengthening by NSM and PNSM techniques has been evaluated using the NLFEA method after being calibrated against a reputable published experimental work from the literature. However, this study focuses on the performance of NSM and PNSM with various FRP diameters, maintaining the ACI440.2-23 bar diameter to the groove size limitation of 1.5. Meanwhile, it was designed on two main categories: various FRP diameters with different reinforcement ratios and groove numbers with the same reinforcement ratio. Five FRP diameters have been examined (8, 10, 12, 14, and 16) mm with groove sizes of (12, 15, 18. 21, and 24), respectively. Two FRP materials (Basalt and Glass), three prestressing numbers (0, 30, and 50) %, and groove numbers (one or two). It has been found that the yielding stiffness undergoes a 35% increase under increasing the PNSM bar diameter by 2 mm compared to 40% and 45% for prestressing levels of 30 and 50%, respectively. Besides, the cracking load is affected by 0.6% compared to 3.5% and 25% for yielding and ultimate loading. Furthermore, it has been found that the prediction of the cracking and ultimate capacities is different for PNSM rebars where differences exist and decrease under increasing the prestressing level and FRP diameter.