Study On Influence Of Connection Defects On Function Of Half-grouted Sleeve Splicing Of Rebar

Half-grouted sleeve splicing of rebars is the core of precast assembled concrete structure,which is quite important to the integrated performance of structure.The different degrees of defects of half grouting sleeves will remarkably increase the risks of precast concrete structures.By studying and consulting a large amount of data in practical engineering,the author analyzes the causes of formation,and summarizes the defects in the connection of half-grouted sleeve splicing of rebar into five categories.Including insufficient grout height,insufficient compactness,rebar offset,insufficient anchor rebar length,overtime grouting.In order to better understanding the defects of rebar connections between half-grouted sleeves,the main contents of the pilot study include: 1.The author made one group of standard specimens and five different test groups,including specimens with insufficient vertical grouting height,specimens with insufficient compactness of grout,specimens with rebar offset,specimens with insufficient anchorage depth of rebar,specimens with overtime grouting.2.The uniaxial tension experiments were conducted for the 24 different specimens experimented to analyze the load-slip curve.3.A finite element model was established using ANSYS for uniaxial tensile simulation and stress-strain analysis.The results of the research showed that: 1.The experiment shows that the specimens displayed three destruction modes the thread shear failure,rebar tension fracture,and rebar pull-out due to bond failure.2.When the vertical grouting height is 104mm(80%8d),the anchorage depth between rebar and grout decreases,which leads to the decrease of bearing capacity and deformation capacity,and the failure mode is rebar tension fracture.3.When20% air bubbles are produced in the grout,the anchorage capacity of the grout is not enough to bear the tensile strength of the joint,resulting in the decrease of bearing capacity and deformation capacity,and the failure mode of the specimen is rebar pull-out.4.When the rebar is offset 5mm,the bearing capacity and deformation capacity of the joint decrease,and the failure mode of the specimen is rebar tension fracture.5.When the anchorage depth of rebar decreases from 130mm(8d)to 120mm(7.5d)and 104mm(6.5d),the bearing capacity anddeformation capacity of sleeve joint gradually decrease,and the failure mode of specimen is rebar tension fracture;when the anchorage depth of rebar decreases to 88mm(5.5d),the bond strength of grout no longer satisfies the tensile strength,and the destruction mode of joint changes from rebar tension fracturee to rebar pull-out.