Experimental Study On CFRP Confined Concrete Filled Steel Tube Stub Columns Under Axial Compression

Concrete filled steel tube is a kind of steel and concrete combination structure form,the structure of the internal steel tube of concrete under the constraints of the role in the three-way compression state,after strength is improved,and steel tube for stability to enhance internal concrete,concrete filled steel tubular give full play to the interaction of concrete and steel tube,the bearing capacity and ductility of the member is also improved.In recent years,with the development of super highrise building and long-span bridge,on the section size of main stress components and the load bearing ability put forward higher requirements,compared with the ordinary strength concrete filled steel tube component,high strength and ultra high strength concrete filled steel tube,can effectively decrease the size of the structure,reduce its weight,and can raise the bearing capacity of components.It is found that the ultra high strength concrete filled steel tube can be used to increase the strength of concrete and improve the ductility of ultra high strength concrete.However,due to the large brittleness of ultra-high strength concrete,the constraint effect of the steel tube is reduced,the bearing capacity is lower and the ductility is poor.And the corrosion of steel tube is a common problem of concrete-filled steel tube structure.In order to strengthen the constraint effect of high strength and ultra high strength concrete filled steel tube,improve its ductility at the same time,combining with the former high strength and ultra-high strength concrete filled steel tube and constrains of CFRP concrete research,we put forward the concept of CFRP constraint ultra-high strength concrete filled steel tube,it is using CFRP external paste in ultra-high strength concrete filled steel tube structure,can enhance the effect of restraint of the ultra-high strength concrete filled steel tube,increasing the capacity and ductility of the increase,and can reduce the amount of steel structure dead weight,still can rise to protect steel tube,reduce the steel tube corrosion problems.In this thesis,CFRP confined concrete-filled steel tube is studied,and its axial compression performance is studied.The specific contents are as follows:(1)Completed six concrete filled steel tube stub columns and 12 CFRP confined concrete filled steel tube stub columns under axial compression,studied the coefficient of concrete strength,restraint coefficient,and the number of CFRP layer parameters influence on the mechanical properties of the specimens.It is found that the failure mode of CFRP confined high strength and ultra high strength concrete filled steel tube is easy to be presented as shear failure,and carbon fiber cloth can significantly improve the ductility of ultra high strength concrete filled steel tube.(2)On the basis of reasonable calculation assumption,the formula for calculating the bearing capacity of CFRP confined concrete filled steel tube stub columns under axial compression is derived.Will formula is derived and the existing three other formulas for bearing capacity calculation of test component,and the test of bearing capacity are compared,and the results showed that the formula is derived the calculation result has good agreement with the test results.(3)The finite element simulation analysis was carried out on the specimen with ABAQUS software,compared with the test results,established for analysis calculation model for analysis CFRP confined ultra high strength concrete filled steel tube stub columns under axial compression,provide the basis for the theoretical analysis and engineering practice.