Search Results (3)

Strengthening of reinforced concrete (RC) structures has become a primary challenge in civil engineering. Different materials and procedures have been used in order to repair or strengthen RC structures. In this research, the NSM-Basalt Bar (NSM-BFRP) technique was used to strengthen high-strength reinforced concrete beams in flexure and shear. Twelve beams were designed, constructed, and tested under four-point loads. Six of them were designed to have insufficient longitudinal steel reinforcement to make sure that the failure would be a flexural failure in the control beam. Whereas, the other six specimens were designed to have insufficient transverse steel reinforcement to make sure that the failure will be a shear failure in the control beam. All RC beams were strengthened using NSM-BFRP with different configurations except control specimens. The load deflection curve, the cracking pattern and the failure mode were evaluated. The experimental results reveal that NSM-BFRP bars significantly enhance the ultimate load capacity of high-strength concrete beams, with flexural capacity improvements of up to 33.33% and shear capacity enhancements of up to 63.5%. However, the use of BFRP bars also led to a shift in failure modes from flexural to shear, particularly in specimens with increased flexural reinforcement. The findings suggest that while NSM-BFRP bars are highly effective in strengthening concrete beams, careful consideration of the reinforcement configuration is necessary to avoid premature shear failure and ensure balanced structural performance. Full article

Damage often develops in glued laminated timber members under high bending loads due to natural defects in the timber, which results in their low load-bearing capacity and stiffness. In order to improve the bending mechanical properties of glulam beams, a new type of longitudinal glulam reinforcement with pre-stressed basalt fibre-reinforced polymer composites (BFRP) was developed using the Near Surface Mounted (NSM) technique. The strengthening method consisted of two pre-stressed BFRP bars glued into the grooves at the bottom side of the beam; meanwhile, for the second strengthening alternative, the third BFRP bar was embedded into the groove at the top side of the beam. Therefore, an experimental study was carried out to verify this strengthening technique, in which fifteen full-size timber beams were tested with and without bonded BFRP bar reinforcement in three series. According to the results of this experimental study, it can be seen that the effective load-bearing capacity of the reinforced beams increased up to 36% and that the stiffness of the beams increased by 23% compared to the unreinforced beams. The tensile stresses in the wooden fibres were reduced by 11.32% and 25.42% on average for the beams reinforced with two and three BFRP bars, respectively. On the other hand, the compressive stresses were reduced by 16.53% and 32.10% compared to the unreinforced beams. The usual failure mode saw the cracking of the wood fibres at the defects, while for some specimens, there were also signs of cracks in the epoxy adhesive bond; however, the crack propagation was, overall, significantly reduced. The numerical calculations also show a good correlation with the experimental results. The difference in the results between the experimental and numerical analysis of the reinforced and unreinforced full-sized beams ranged between 3.63% and 11.45%. Full article

This paper reports the numerical simulation of earthquake-damaged circular columns repaired with the combination of near-surface-mounted (NSM) basalt fiber reinforced polymer (BFRP) bars with external BFRP sheets jacketing at quasi-static loading. The numerical modeling was carried out with the nonlinear OpenSees software platform by using the BeamWithHinges element. In the simulations, the effect of the previous earthquake damage on the behavior of the repaired columns was taken into account, and a simple and effective material damage-accumulation model is proposed to modify the constitutive of materials in the unrepaired regions of the repaired columns. The developed numerical models were validated by comparing their quasi-static findings with those obtained from a previous experimental program, and a good agreement can be observed. Furthermore, the efficiency of the repair technique used in tests is evaluated via the developed numerical model. Full article