| Reinforced concrete is one of the most widely used building materials at present.In recent years,with the aggravation of terrorist activities and frequent natural disasters such as earthquakes,reinforced concrete structures will inevitably be impacted,in which reinforced concrete beams are important load-bearing members.Its performance needs in-depth study.At the same time,due to the influence of its own characteristics and later decoration construction and other factors,the reinforced concrete material will contain initial defects and artificial defects in the later stage.At present,the research objects of scholars are basically undefective reinforced concrete,and there are few dynamic mechanical studies on reinforced concrete structures with defects.Based on this,this paper establishes a three-dimensional finite element model of reinforced concrete beams without defects by using the large-scale nonlinear finite element program LS-DYNA,according to the existing impact test conditions of reinforced concrete beams in references.After verifying the reliability of the model,we first study the influence of single spherical defects on the impact performance of reinforced concrete beams,and then study and analyze the effects of multiple spherical defects on the impact performance of reinforced concrete beams.The main conclusions are as follows:(1)Under the impact load,the spherical defect with a diameter lower than 30 mm has almost no effect on the impact resistance of reinforced concrete beams.When the diameter of spherical defect is higher than that of 30 mm,the influence of spherical defect on the impact performance of reinforced concrete beams increases gradually with the increase of diameter.(2)When the spherical defect is above the neutral layer of the beam,the defect has almost no effect on the beam;when the spherical defect is below the neutral layer of the beam,with the position of the defect moving down,the influence of the defect on the impact resistance of the beam becomes greater.(3)In the case of the same impact mass and impact position,the effect of spherical defects on the impact resistance of the beam changes from no obvious effect to a certain positive correlation with the increase of speed.(4)When the impact mass,velocity and the size and position of the spherical defect are the same,the failure mode of the reinforced concrete beam gradually changes from bending failure to shear failure as the impact position moves from the middle of the span to the support.the failure shape of the beam is mainly affected by the change of the horizontal distance between the impact position and the bearing,but the influence of the spherical defect is not obvious.(5)When multiple spherical defects exist at the same time,the influence of their position distribution on the impact resistance of the beam is greater than that of the simple quantity on the impact resistance of the beam. |
