Research On Shear Resistance Of Beams With Cracks And Without Web Reinforcement And Carbon Fiber Sheet Reinforcement

The shear failure of reinforced concrete beams is brittle failure,which is more harmful.Many scholars have conducted research on the shear resistance of reinforced concrete beams.In actual engineering,there are a large number of working conditions of internal cracks and defects in reinforced concrete beams,which is not conducive to the normal performance of the shear performance of reinforced concrete beams,and there are certain hidden safety hazards.It is generally believed that the shear bearing capacity of reinforced concrete beams consists of two forms:the contribution of the concrete part and the contribution of the web reinforcement,and the contribution of the concrete part is usually taken as the shear bearing capacity of the beam without web reinforcement.This paper studies the shear performance of beams with cracks and without web reinforcement,which can further improve the theoretical system of shear performance of beams with web reinforcement.In order to effectively strengthen the cracked beam,this paper uses carbon fiber cloth for side bonding to improve the shear resistance of the cracked beam.Certain conclusions have been obtained,which has high application value.In this thesis,the method of indoor test was adopted.The beam model without web reinforcement was used as the test object.The pre-set cracks were used to simulate the existing cracks.A three-point bending load test was carried out to study the effect of the existing cracks on the test beam at different positions and angles.The influence of the shear performance of the cracked beam concrete part.At the same time,in order to ensure that the cracked beam can be effectively strengthened to meet the normal working requirements,the effect of different angles of side sticking of carbon fiber cloth on the shear performance of the cracked beam was further studied.The stress state of typical test conditions is calculated numerically,and compared with the test results,the test results are explained.At the same time,through the analysis of the shear mechanism of the beam with cracks and no web reinforcement,the theoretical model of tie-bar arch is used to analyze and explain the shear performance of the beam with cracks and the law of crack propagation.Finally,combined with the experimental data,the reinforcement mechanism of the side-bonded carbon fiber cloth reinforced beam with cracks is analyzed,which can provide guidance for production practice.Studies have shown that during the three-point bending loading process of reinforced concrete beams,the existing cracks in the beam have a weakening effect on the shear resistance of the concrete part of the beam.When the existing cracks are located in the middle of the beam,the distance between the crack tips of the existing cracks The closer the center of the beam bottom,the greater the weakening effect on the shear bearing capacity of the concrete part of the beam with cracks;when the existing cracks are located within the basic arch of the beam side,the angle of the existing cracks and the basic arch of the concrete beam are more closely aligned,The greater the weakening effect on the shear bearing capacity of the concrete part of the beam with cracks.In addition,when the verticality of the existing crack in the beam span is higher,the crack tip attracts the stronger the horizontal position of the crack initiation point at the bottom of the beam;when the angle of the existing crack on the beam side is more closely aligned with the basic arch When it is high,the cracks at the bottom of the beam are easier to extend through the two crack tips of the existing cracks;when the angle of the existing cracks on the side of the beam and the basic arch are lower,the cracks at the bottom of the beam can expand to the middle area of the existing cracks.When the angle of the existing cracks on the beam side and the basic arch of the concrete beam are relatively high,the carbon fiber cloth is used to strengthen the beam with the cracks.The higher the perpendicularity of the paste direction to the existing diagonal cracks,the more the carbon fiber cloth has the right to the cracks.The better the reinforcement effect of the beam,the better the shear bearing capacity of the concrete part of the beam with cracks can be improved.