Impact Study Of Grouting Defects On The Mechanical Property Of Prestressed Concrete Beam

The prestressed concrete girder bridges are adapt to the development of large span structure,and have been widely used in the civil engineering construction,which have many advantages,such as materials saving,the weight of the structure reducing,the crack of concrete structure preventing and good mechanical performance.The grouting quality of prestressed concrete bridge is one of the key points to ensure the construction quality.In this dissertation,the theoretical and experimental researches are carried out on the problem of grouting in prestressed concrete channel.Firstly,the influence of the concrete grouting quality on the performance of concrete structure is analyzed.The influence of prestressed duct grouting defect size and distribution position on flexural behavior of prestressed concrete beams are analyzed by scaled experiments.A numerical model of prestressed beam is established for the analysis of the performance of a beam structure with different duct grouting defects.The numerical and experimental results show that the length and the bearing capacity of prestressed concrete are approximately linear.The stiffness degradation would occur earlier with large defects.Secondly,the full scaled experiment of the prestressed concrete beam with different defect is carried out to study the mechanical property.It can be concluded that the ultimate flexural capacity of the box girder is weakened along with the increase of the length of the defect.When the defect is in the position of the box girder,the ultimate flexural capacity of the box girder is weakened more seriously.Finally,the experimental study on the durability of influence prestressed concrete beams are carried out to study the influence of defects on the mechanical properties of prestressed concrete beams.The results show that the local corrosion of prestressing tendons without grouting is more serious than that of the prestressed reinforcement.In the extreme case,the influence of the prestressed tendon fracture due to the defect of prestressed channel grouting on the bearing capacity of member is analyzed,and theexperimental results show that under this case,the ultimate bending load of member weaken more than 20%,in which the mid span prestressed tendon fracture has the greatest effect on the bearing capacity of the member.In order to overcome the influence of grouting defect on the prestressed concrete structure,the feasibility of the new type of intelligent circulating channel grouting process is studied.Through the establishment of numerical analysis model of fluid,the simulation of the process of circulating slurry is carried out.The results show that slurry density can be further improved along with the extension of the cycle grouting time for a 30 m span of the prestressed concrete beam.The effects of grouting pressure,diameter and length of cycle parameters such as grouting quality are studied.The relationship between circulating pressure grouting pressure and length parameters are determined.Finally,combined with the practical engineering,the circulating pressure grouting technology is studied systematically in this dissertation.It can be concluded that the circulation grouting technology can ensure the grouting effect of the prestressed channel is full and dense.