A Study Of The Mechanical Properties Of Grout Sleeve Considering Different Defect Distributions

In prefabricated buildings,grout sleeve connection is a more common way to connect reinforcement,grouting defects and connection performance will directly affect the safety of the entire structure.The grouting process is one of the more important aspects of the construction process,but in practice it is easy to see how the grout is not full.At present,there is little research into the performance of defective grout sleeve joints,especially in terms of the mechanical properties of grout defects at different locations.The non-linear finite element analysis of the test model is carried out,and combined with structural tests and theoretical analysis,the force performance of grout sleeve with different defect distribution is systematically investigated,and the main research contents and results are as follows.1.In order to study the mechanical properties of grout sleeve with different defect distributions,49 sets of specimens with different specifications were made and monotonic axial tensile tests were carried out considering factors such as defect length and different defect distributions.It has investigated the damaged procedure and damaged morphology,with an analysis of the consequences of defects on the mechanical properties of grouted sleeves.The study showed that the specimens with defect lengths of 1D and 2D were all damaged by pulling the reinforcement,while the specimens with defect lengths of 3D had both forms of damage depending on the distribution of defects.2.The load carrying capacity of the specimens with defect length in 2D and 3D are: class A < class B <class C ≈ class H,class A < class B < class C < class H respectively.The ultimate displacement of each corresponding numbered specimen of class B and C in defect length 2D shows that class C is larger than class B.For specimens that have a defect length of 3D,the ultimate displacement will increase with increasing load capacity.Through movement defects,it is found that if there is vertical overlap of defects in the upper middle section of the specimen,it will greatly affect the load bearing capacity of the specimen.3.The analysis of the bond strength of the grout was carried out using mechanical theory.The conclusions are as follows: the bond strength values calculated for each specimen were compared with the test values using the Mander model to derive a grout bond strength coefficient with a range of values between0.83-0.90.The theoretical value of grout compressive strength was also calculated to be less than the actual value.To make the strength more accurate,a correction factor for the compressive strength of the grout was proposed,which was calculated to be in the range of 1.20-1.43.Based on the occurrence of reinforcement pull-out damage specimens in the test,combined with the theoretical formula of bond strength can be inverse to the minimum value of reinforcement anchorage length.When the overall anchorage length of the reinforcement is not less than 5.51 D,the grout sleeve can be considered to meet the force performance requirements.4.ABAQUS finite element simulations were carried out on specimens with annular defects,control specimens and specimens with defects of 3D length where reinforcement pull-out damage occurred.The study shows that the damage form of each specimen model in the simulation is consistent with the test results,but the ultimate tensile stresses of the simulated specimens are all smaller than the test values,with the ratio of simulated ultimate tensile stresses to test values ranging from 0.91 to 0.95.The Mises stress cloud of the grout in the specimens shows that the grout at the sleeve stiffening ribs and near the defective locations is prone to stress concentration.The stress distribution law at the internal and external interfaces of the grout in the presence of defects was analysed.