Experimental Research On Axial Pressure Performance Of FRP-stainless Steel Pipe-seawater Sea Sand Concrete Column

In this paper,a FRP-Stainless Steel Pipe-Seawater Sea Sand Concrete Column(FRPStainless Steel Pipe-Seawater Sea Sand Concrete Column)is systematically tested and theoretically analyzed.The FRP-stainless steel pipe-seawater sea sand concrete column in this test is a composite column composed of three materials: external CFRP,internal stainless steel pipe,and seawater sea sand concrete in the stainless steel pipe.Seawater and sea sand concrete can save river water and river sand resources,and achieve the purpose of protecting the ecological environment;internal stainless steel pipes will not be corroded by seawater and sea sand concrete,and can also increase the ultimate bearing capacity and ductility of seawater and sea sand concrete;external CFRP is also It will be corroded by seawater sea sand concrete,and the external CFRP can effectively restrain the internal stainless steel pipe seawater sea sand concrete to improve the bearing capacity and ductility.The main research has the following points:(1)Through 6 sets of FRP-stainless steel pipe-seawater sea sand concrete columns,monotonous axial compression test was conducted to study the three parameters of CFRP layer,steel pipe thickness and concrete strength to explore the changes of its mechanical properties.The results show that: FRP-stainless steel pipe-seawater sea sand concrete columns are all fracture and failure of CFRP near the middle;when the number of CFRP layers increases,FRP-stainless steel pipe-seawater sea sand concrete columns have higher ultimate bearing capacity and ductility.When the thickness of the stainless steel pipe increases,the ultimate bearing capacity and ductility of the FRP-stainless steel pipe-seawater sea sand concrete column are higher;when the strength of the concrete increases,the ultimate bearing capacity of the FRP-stainless steel pipe-seawater sea sand concrete column is more High,but its ductility is lower.(2)Through 7 groups of FRP-stainless steel pipe-seawater and sea sand concrete columns,the cyclic axial compression test was conducted to study the three parameters of CFRP layer number,steel pipe thickness,and loading rules to explore the changes in its mechanical properties.The results show that the failure form of FRP-stainless steel pipe-seawater sea sand concrete column under cyclic axial pressure is similar to that of monotonic axial pressure,all of which are the fracture failure of CFRP near the middle;the stress-strain curve of the specimen under monotonic axial pressure can be approximated As the envelope of the stressstrain curve under cyclic axial compression;multiple cycles of axial compression will cause more damage to the confined seawater and sea sand concrete than single cycle axial compression.And put forward a new plastic strain formula.(3)Combined with the existing theoretical model of FRP confined concrete,a new design model of monotonous axial compression of FRP-stainless steel pipe-seawater sea sand concrete column is proposed,and the model value is compared with the experimental value.The results show that: FRP-stainless steel proposed in this paper The new design model of the pipe-seawater sea sand concrete column has better prediction effect and can provide theoretical guidance for this type of component.