Experimental study on flexural behavior of damaged concrete beams strengthened with high ductility concrete under repeated load

In this study, pre-damaged beams were repaired and strengthened using high ductility concrete (HDC), and the extent of damage at different stages of the beam was measured using an ultrasound method. Nine concrete beams were fabricated, one of which was a control beam and the rest were HDC-reinforced beams. The investigated parameter was the thickness of the HDC reinforcement layers, and four thickness values were investigated. Damage equations and thresholds were obtained on the basis of damage mechanics and probabilistic statistical analyses. The results showed that as the thickness of the reinforcement layer increased, the ultimate load-carrying capacity and cracking load of the reinforced beam gradually increased while the residual deforma-tion gradually decreased. Compared with the load-carrying capacity of the test beam in Group A, that of the test beam in Group D increased by 46.3%, the residual deformation reduced by 32.5%, and the cracking load increased by 55.7%. The comparison between beams in Groups A and D was performed in terms of ultimate load-carrying capacity, crack control capacity, and degree of damage. The comparison showed that as the thickness of the reinforcement layer increased, the load-carrying capacity of the structure increased while the degree of damage decreased; however, this behavior was not suitable for the healing of the structural cracks. Therefore, the reinforcement measures and structural damage determination methods proposed in this study are simple and convenient, easy to deploy on a large scale, and valuable to the further development of the industry.

Automated summary

In this study, pre-damaged beams were repaired and strengthened using high ductility concrete (HDC), and the extent of damage at different stages of the beam was measured using an ultrasound method. The results showed that increasing the thickness of the reinforcement layer improved the load-carrying capacity and cracking load of the beam while reducing residual deformation. However, this method was not suitable for repairing structural cracks. The proposed reinforcement measures and structural damage determination methods are simple and convenient, and valuable to the further development of the industry.