Study On Shear Behavior Of Seawater Sea-Sand Concrete Beams Strengthened With Superelastic SMA Bars

With the rapid development of the current society,a large amount of concrete will be used in infrastructure construction,which will inevitably consume a large amount of fresh water and river sand resources,resulting in the destruction of the ecological environment.In order to alleviate the environmental damage and resource consumption,the use of seawater sea-sand to prepare concrete has become one of the research hotspots in the field of new building materials and structures.However,the chloride ion content in seawater sea-sand is high,which will bring corrosion problem to steel bar and seriously affect the service life of engineering structure.Shape Memory Alloy(SMA)is a new kind of material,which has super elasticity,Shape Memory effect and good corrosion resistance.It can not only avoid corrosion problems,but also realize the self-repair and self-reset function of components or structures when used in seawater sea-sand concrete structures.Based on this,this paper carries out experimental and theoretical research on the shear performance of seawater sea-sand concrete beams with SMA stirrups,mainly including:(1)Uniaxial compression test of seawater sea-sand concrete specimens,tensile test of SMA bar,analysis of strain amplitude and number of cycles on the mechanical properties of SMA bar,lay the foundation for subsequent experimental research.In this experiment,four-point loading was used to conduct one-way low-cycle repetitive loading with displacement control.The effects of different types of stirrup,different types of longitudinal reinforcement,shear-span ratio and stirrup spacing on the shear performance of SMA seawater sea-sand concrete beams were studied.(2)The experimental data of five seawater sea-sand concrete beams were compared and analyzed,this paper compares and analyzes through the crack width in the process of test,information acquisition boards such as records of displacement experiment,draw the load-displacement curve,skeleton curve,since the restoration capacity curve and stiffness degradation curve,also used the DIC in the process of test equipment,for auxiliary observation,The shear behavior of SMA seawater sea-sand concrete beam was studied.(3)The finite element model of SMA seawater sea-sand concrete beam was established by ABAQUS software,and the numerical simulation analysis was carried out.The results of numerical simulation,such as stress-strain cloud diagram,load-displacement curve and maximum bearing capacity,are obtained,and compared with the experimental results,which shows that the numerical simulation results are in good agreement with the experimental results,and the correctness of the model is verified.(4)Based on the existing concrete flexural member of shear model and design specifications from all countries,with truss arch model and the theory of limit equilibrium model,this paper derived the superelastic SMA reinforced the seawater sea-sand formula of ultimate shear capacity of concrete beams,and were compared with experimental value,verify the applicability of the proposed formula.The test results show that using SMA stirrups instead of ordinary steel stirrups,the shear bearing capacity of specimens is increased by 19.4%,ductility is increased by 65.8%,and crack width is relatively wide.However,the cracks are basically closed after unloading,which has a certain repair effect;Longitudinal reinforcement using SMA material,ductility further increased by 11.4%,in the bearing capacity decline stage,the bearing capacity decline rate is slow;Increase the shear span ratio of specimens,SMA stirrup can still increase the ductility of specimens,improve 20%.Therefore,SMA can enhance the shear performance of sea-sand concrete beams,increase ductility,and reduce the shear brittle failure tendency of beams.