Research On Influence Factors Of SMA Concrete Beam Self-repairing Performance

Shape memory alloy(Shape memory alloy,SMA)as one of the smart materials,due to large deformation can be recovered,in the restricted recovery can produce a great driving force,resistance is sensitive to strain,high damping properties,resistance fatigue performance,widely used in construction,aviation,aerospace,military and medicine etc.In the field of construction engineering,because the application characteristic of SMA material,SMA material is used in the seismic isolation structure design,structure vibration control,reinforcement and repair and structure detection.Made of SMA material made of various dampers,seismic isolation and shock absorption support,SMA concrete intelligent structure has achieved remarkable results.However,reinforcement application in detection and repair of the SMA concrete structure is affected by many factors.In this paper,we research on those factors of SMA concrete structure repairing,and how to utilize these factors make the SMA concrete structure self-repairing effect to achieve the optimal.Firstly,mechanics performance Study of SMA.Heat treatment to SMA material,to change the temperature of phase change of the SMA material,make it has good material properties.Then the heat treated SMA materials by differential scanning calorimeter(Differential Scanning Calorimeter,referred to as DSC)test,get the alloy heat flow and temperature diagram,so as to determine the temperature of phase change of materials.On this basis,the tensile test of SMA wire,understand the mechanics properties of SMA wires.Secondly,test pieces making and bond strength test.By test,get test specimens load-slip curves,and the average bond stress is 394.33N.That smooth bond force SMA wire and concrete is smaller,effects on self-repairing is also small.So in unbonded length effect on SMA concrete beam repair test,before recovery test we need to install plate and anchorage on both ends of beam anchor.Once again,influence factors effect on the self-repairing performance of SMA concrete beam.By three points bending tests get the mechanical properties of the beam Through the analysis of experimental phenomena and data find that the more value of SMA wire pretension the bigger bearing capacity of the beam;the longer unbonded length of SMA wires,the lower bearing capacity of the beams.Then by using SMA wire shape memory and super elasticity characteristics,repair test of concrete beam.The test shows that which pretension value is 25%to 35%of the limit pretension value,crack restoration the situation is relatively good;the longer unbonded of SMA wire,the more well repairing of crack of test beam.Finally,factors affecting the performance of SMA concrete beam repair and the engineering application analysis.Through the formula derivation and experimental data analysis we can find through analysis the member force estimated SMA wire’s strain values due to load,to find the optimal value of the pre tension.In engineering applications,it can synthetically treat of two kinds of influence factors(pretension and unbonded length).By pretension SMA wire embedding in concrete beam or installed pretension SMA wire outside the concrete beam to achieve the optimal repair of cracks,and according to the actual situation to choose suitable engineering realization way.