Abstract: In order to study the dynamic fracture properties of FRP strengthened concrete, the three-point bending experiment with different initial crack-depth ratios was carried out under dynamic loading. The effects of crack-depth ratios on the fracture parameters were analyzed. Combined with Pearson Correlation Coefficient formula, the correlation between crack-depth ratios and fracture parameters was quantitatively verified. The conclusions could be drawn that, there are three critical points in the damage process: the crack initiation point, first peak point and ultimate bearing capacity point. With the increase of crack-depth ratio, the crack initiation load decreases, but the first peak load and ultimate load increase first and then decrease. The stress intensity factors of three points also increase first and then decrease. The increment of critical crack-depth ratio and flexibility coefficient are related to crack-depth ratio, which could reflect the effect of crack-depth ratio on the deformation capacity of FRP strengthened concrete.

Abstract: In order to study the dynamic fracture properties of FRP strengthened concrete, the three-point bending experiment of FRP strengthened concrete beams with five different initial crack-depth ratios was carried out by using MTS-810 hydraulic servo experiment machine. The initial crack-depth ratios are 0.2, 0.3, 0.4, 0.5 and 0.6 respectively. The effects of different initial crack-depth ratios on the load-crack mouth opening displacement (CMOD) curves, failure process, increment of critical crack-depth ratio and flexibility coefficient of FRP strengthened concrete beams were analyzed through displacement controlled monotonic loading method. Combined with Pearson correlation experiment formula, the correlation between initial crack-depth ratios and different fracture parameters was quantitatively analyzed. The conclusions could be drawn that, there are three obvious critical points in the fracture damage process of FRP strengthened concrete beams: the starting point of concrete crack, the first peak point and the ultimate bearing capacity point. As the increase of initial crack-depth ratios, the crack initiation load decreases, but the first peak load and ultimate load increase first and then decrease. It is found that the stress intensity factors (SIFs) of the three critical points increase first and then decrease with the increase of the initial crack-depth ratio, and when initial crack-depth ratio of concrete beams is 0.4, three kinds of SIF all reach the maximum value. The increment of critical crack-depth ratio and flexibility coefficient of FRP strengthened concrete beams are related to initial crack-depth ratio, which could be used to reflect the effect of initial crack-depth ratio on the deformation capacity of concrete specimens. Keywords: FRP strengthened concrete; dynamic fracture; initial crack-depth ratios; stress intensity factors; increment of critical crack-depth ratio; flexibility coefficient

Abstract: In order to study the dynamic fracture characteristics of FRP reinforced concrete, the three-point bending experiment of FRP reinforced concrete beams with different initial crack-depth ratios was carried out by using MTS-810 hydraulic servo experiment machine. The initial crack-depth ratios are 0.2, 0.3, 0.4, 0.5 and 0.6 respectively. The effects of different initial crack-depth ratios on the load-crack opening displacement curve, failure process, the increment of critical crack-depth ratio and flexibility coefficient of FRP reinforced concrete three-point bending beam specimens were analyzed by displacement controlled monotonic loading method. Combined with Pearson correlation experiment formula, the correlation between initial crack-depth ratios and different fracture parameters was quantitatively analyzed. The conclusions can be drawn that, there are three obvious critical points in the fracture process of FRP reinforced concrete three-point bending beam: the starting point of concrete crack, the first peak point and the ultimate bearing capacity point. With the increase of the initial crack-depth ratio, the crack initiation load decreases, but the first peak load and ultimate load increase first and then decrease. It is found that the stress intensity factors of the three critical points increase first and then decrease with the increase of the initial crack-depth ratio, and when the initial crack-depth ratio is 0.4, the three kinds of stress intensity factors all reach the maximum value. The increment of critical crack-depth ratio and flexibility coefficient of FRP reinforced concrete beams are related to the initial crack-depth ratio, which can be used to reflect the influence of initial crack-depth ratio on the deformation capacity of concrete specimens. Keywords: FRP reinforced concrete; dynamic fracture; the initial crack-depth ratios; stress intensity factors; increment of critical crack-depth ratio; flexibility coefficient