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This paper presents experimental and finite element model (FEM) on reinforced concrete (RC) beam behavior strengthened by near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) strips subjected to pure torsional loading. Seven rectangular reinforced concrete RC beams of 250 mm 9 250 mm 9 1600 mm were constructed and tested considering the effect of length, inclination, arrangement of longitudinal and scheme of NSM-CFRP strips. The outcomes of the tests indicated remarkable enhancement in the behavior of torsional strengthened beams using NSM-CFRP strips. In general, the beams strengthening with inclined CFRP-NSM strips exhibited an increase in torsion moment strength and angle of twist more than the beams strengthening with vertical CFRP-NSM strips. The experimental measured results are validated with a 3D numerical simulation carried out using nonlinear finite element (FE) modeling. Finally, it can be seen that the calculated numerical torsional moment-angle of twist behavior is in agreement with the experimental results for all RC beams.

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The effectiveness of near-surface-mounted carbon-fiber-reinforced polymers on strengthening and repair of self-compacted concrete slabs was investigated experimentally and numerically. Twenty slabs were cast (10 one-way and 10 two-way) and tested under four-point load. Strengthening and repair effectiveness was investigated on slabs using near-surface-mounted carbon-fiber-reinforced polymer strips with straight and inclined orientation. Repair was performed on eight slabs using near-surface-mounted carbon-fiber-reinforced polymer strips with an orientation based on the best cost/capacity ratio, with two preloading levels: 35% and 50% of the ultimate load of the control slab. The results showed that using near-surface-mounted carbon-fiber-reinforced polymers increases the ultimate strength of one-way strengthened self-compacted concrete slabs (45%–163%) for both strip orientation, with the straight orientation performing better. Also, the cracking load and stiffness increased, while deflection decreased. The increase in ultimate strength for strengthened two-way slabs was 15% to 17%. The ultimate deflection and toughness of the two-way strengthened slabs increased 43% and 34%, respectively. Using near-surface-mounted carbon-fiber-reinforced polymers restored the load capacity of repaired one-way and two-way slabs but was more effective for one-way slabs. The repaired one-way slabs regained up to 223% of the control slabs’ ultimate strength, with a significant increase in stiffness (296%). The repaired two-way slabs regained up to 116% of the control slabs’ ultimate strength. The strength was higher in the case of the 50% preload compared to 35% preload. The finite element model shows somehow a reasonable capability of predicting the experimental behavior with a gap in terms of the stiffness and the maximum load.