Study On Bearing Capacity Of Precast Concrete Beam And Slab Members

As a kind of building products,the quality of prefabricated components directly affects the safety and reliability of prefabricated buildings.Many factors during the fabricated process of prefabricated members will lead to different degrees of damage,which will have an impact on their product quality.This paper focuses on two serious representative issues,one is the demoulding and hoisting adhesion of laminated slab,the other one is the non-compactness of grouting of reinforcement sleeve for prefabricated reinforced concrete beam in the stage of component fabrication.The influence of fabrication defects on the bearing capacity of components is investigated.The main research work is as follows:The four-corner,one-corner and intermediate bonding conditions of the demoulding and lifting of the laminated plate were conducted through the finite element analysis(FEA)which is based on the determination of reasonable lifting point position.The influence of three different bonding conditions was discussed on the bearing capacity of the prefabricated laminated plate.The bending capacity of laminated plates around weak axes decreases obviously when there is adhesion,but the bending capacity around strong axes basically remains unchanged.For the same bending direction,the bending capacity decreases obviously under the condition of intermediate adhesion.On the basis of unidirectional tensile test of the reinforcement sleeve drawing parts,this paper evaluated the influences of tensile behavior of high strength reinforced bar grouting sleeve connections of different diameters and density.For the steel bar grouting sleeve with diameter of 32 mm,when the compactness of the steel bar grouting sleeve is 60%,its test load accounts for about 6%of the test load of the steel bar grouting sleeve with 100%compactness.When the compactness of the sleeve grouting reaches 80%,its connection performance is greatly improved,and its test load accounts for 83.5%to 87%of the test load with 100%compactness of the grouting sleeve.When the grouting compactness is 50%,the average tensile bearing capacity of the grouting sleeve is only about 10%of the grouting compactness 100%.When grouting compactness is increased to 70%,the average tensile bearing capacity of pulled-out specimens can reach about 50%of the 100%grouting compactness specimens;when grouting compactness continues to increase to 90%,the average tensile bearing capacity of pulled-out specimens has basically the same as that of 100%grouting compactness specimens.The bearing capacity test of prefabricated concrete beams with 70%compactness of grouting sleeve is conducted.Based on the principle of equivalence of steel cross-section,the prefabricated reinforced concrete beams with grouting sleeve are simulated through FEA.On the basis of verifying the feasibility of the modelling method,the influence of the compactness of grouting sleeve on the ultimate bearing capacity of prefabricated reinforced concrete beams is further studied.The compactness of reinforced grouting sleeve has an important influence on the bearing capacity of beams.When the compactness of reinforced grouting sleeve is 70%,the decline of bearing capacity of precast reinforced concrete beams is sudden and there will be potential safety risks.Attention should be paid to the non-compactness of sleeve grouting of large diameter and high strength reinforced beams.The numerical simulation method based on the principle of equivalent section area of reinforcement can obtain the bearing capacity of beam members which matches well with the experimental results.The results indicate that the bearing capacity of prefabricated reinforced concrete beam was improved with the increase of the compactness of reinforced grouting sleeve.