Research On The Influence And Control Of Cracks In Reinforced Concrete Thick Slab Members

With the rapid development of economy,the demand of electric power energy is constantly climbing.Under the guidance of the concept of green development,our country has increased the development and investment of new clean energy such as nuclear power,and the related construction such as nuclear power engineering has ushered in great development opportunities.As one of the important components of nuclear power engineering structure,reinforced concrete slab members are easy to crack in the actual construction process because of their large size and high strength.Considering the importance of nuclear safety,it is of great practical significance and broad application prospect to study the crack related problems of thick plate members.In this paper,the influence of vertical penetrating cracks in thick plate members on the shear performance of thick plate members and the crack control effect of anticracking steel mesh technology are studied.The main work is as follows:(1)The shear test of 9 large specimens in 3 groups was designed and completed to explore the influence of the degree of crack self-healing,section area and interfacial reinforcement diameter on the shear properties of the fracture interface of thick plate members,reveal the failure mechanism of the members,discuss the applicability of shear friction theory and specification formula,and give relevant calculation suggestions.The test results show that the degree of self-healing of crack interface is the key to affect the final failure mode of specimens.When the self-healing of cracks is good,the specimens will suffer shear-compression failure.The ultimate bearing capacity of shear-compression failure is related to the strength of reinforcement and concrete.When the self-healing of cracks is poor or unable,direct shear failure occurs.The ultimate bearing capacity of direct shear failure is related to interface reinforcement ratio and interface roughness.For shear checking calculation of crack interface,GB/T 51390-2019 formula can be used in general,and fid Model Code 2010 formula can be used in extreme and special cases.The calculation results all maintain sufficient safety margin.(2)The bending test of 8 large specimens in 2 groups was designed and completed to explore the influence of the protective layer thickness,steel mesh diameter and spacing on the crack control effect of thick plate members,reveal the anti-cracking mechanism of steel mesh pieces,and derive the cracking load calculation formula of members based on the anticracking mechanism.The test results show that before cracks appear,the steel mesh mainly disperses the stress in elastic stage,improves the ultimate tensile in plastic stage and controls the formation of macroscopic cracks to improve the crack bearing capacity of the specimens.After the crack appears,the crack width of the specimens is controlled by adhesion and reinforcement binding force.When the thickness of protective layer is 50 mm and 80 mm,and the steel mesh pieces are configured with 6@150,8@150 and 8@200,the cracking load of specimens can be increased by more than 27.0% and the crack width can be reduced by more than 16.7%.The calculation results of the proposed cracking load formula are in good agreement with the experimental results and can be used to calculate the cracking load of thick plate members in general.(3)Based on the bending test results,a numerical model was established by ABAQUS finite element software,and the anti-cracking effect of steel mesh was analyzed from the perspective of internal stress and damage.The simulation results show that with the decrease of protective layer thickness,the diameter of the mesh reinforcement increases,and the spacing of the mesh reinforcement decreases,the damage degree of components decreases,the crack control effect of steel mesh is enhanced,and the stiffness and bearing capacity of components are effectively improved,but the overall improvement degree is limited.