| Reinforced concrete beam member is the most basic force member in the design of civil engineering structure.In most cases,the beam is bent or shear.One of the premise of beam design is to analyze the shear mechanism of the beam,showing that obvious brittleness is one of the characteristics of shear failure of ordinary reinforced concrete beam.In practical engineering problems,crack problems are also common,which seriously affects the safety and usability of the structure,and brittle failure brings great difficulties to the follow-up repair work.At present,the research of fiber concrete at home and abroad is increasing day by day.Fiber concrete has high ductility,high strength,and can effectively inhibit the development of cracks.If it is properly applied to the key structural parts,it can be very effective to improve the deformation capacity of the structure and make the strength of the structure meet certain requirements,inhibit the development of cracks,increase the ductility of members,reduce the possibility of brittle failure.(1)Polyvinyl alcohol fiber(PVA)is a kind of synthetic fiber,its strength and elastic modulus are relatively high,and good hydrophilicity,easy to bond with cement matrix,in practical application can be used as a better toughening material,in the application can not only make the early plastic crack of concrete can be effectively inhibited,Moreover,the brittleness of concrete materials can be significantly improved and the impact resistance of the structure can be improved.(2)The microcracks in the concrete matrix can be bridged by adding PP fiber in concrete.By effectively controlling the appearance and development of cracks,the crack width of concrete can be effectively controlled and the tensile strength,flexural strength and toughness of concrete can be improved ultimately.In general,the mixed concrete has better strain capacity and energy absorption capacity than the concrete mixed with single fiber.(3)At present,the research results on PP-PVA hybrid fiber concrete at home and abroad are very limited,and the research on the shear performance of PP-PVA hybrid fiber concrete beams is relatively few.Therefore,the influences of fiber type,fiber volume and other parameters on the shear performance of PP-PVA hybrid fiber concrete beams are discussed in this paper.This paper studied the effect of PP-PVA hybrid fiber on the shear performance of concrete beams,designed and studied the optimal mix ratio,made 9 concrete beams with different fiber content,carried out shear experimental study,and hit the corresponding test blocks,measured the strength of each test block and made a summary analysis.According to the experimental results,the influences of fiber volume content and fiber type on the initial crack load,ultimate load,crack evolution and load-deflection curve of PP-PVA hybrid fiber concrete beams under shear were compared and analyzed.The failure process of each fiber concrete beam was described and the damage degree of concrete in compression zone and tension zone between each beam was compared. |
