Experimental Study On Axial Compression Performance Of Thin-walled Square Steel Tube Columns Filled With Phosphogypsu

A new type of cold-formed thin-walled steel wall stud called phosphogypsum-filled thin-walled square steel tube(PFST)column was proposed in this paper.The column consists of a square steel tube and phosphogypsum inside,which meets the characteristics of lightweight.But now the lack of the studies on the properties of PFST columns under axial load,This paper makes a deep study of the axial compressive performance of PFST columns under axial load through.The main contents are shown as below:(1)3 hollow steel tubes(HST)and 36 PFST columns were designed and fabricated with consideration of the section with or without phosphogypsum,water-solid ratio,hollowness ratio and thickness of steel tube.Through axial loading tests.the failure mode,load-deformation curve,load-strain curve,and bearing capacity were analyzed.The test results indicated that the HST short column presented a failure mode of local buckling,the PFST short column presented a failure mode of the “drum shape” failure mode,the intermediate long column filled with phosphogypsum presented a failure mode of elasticplastic instability.Compared with the HST short column,filling phosphogypsum can significantly increase the axial bearing capacity of the specimen.The axial bearing capacity of the PFST column is proportional to the thickness of the steel tube,and inversely proportional to the water-solid ratio of phosphogypsum.The change of the hollow percentage of the specimen has a significant influence on the bearing capacity of the specimen.This is because the water content has a great influence on the strength of phosphogypsum.The change of the hollow percentage of the specimen results in the difference of the water content of phosphogypsum,which further affects the bearing capacity of the specimen.(2)This paper carried out the finite element analysis of the axial compressive performance of HST、PFST column under axial load.and the variation trend of stress and interaction in the whole process of loading is analyzed.By analyzing a large number of parameters of hollowness ratio,thickness of steel tube,steel strength,phosphogypsum strength,slenderness ratio,etc.The different failure modes of short,intermediate long columns is obtained.The effects of various parameters on the axial compression performance of short and intermediate long PFST stud were investigated.The test results indicated that the hollow steel tube stud presented a failure mode of local buckling,the short stud presented a failure mode of the “drum shape” failure mode,the intermediate long stud filled with phosphogypsum presented a failure mode of elastic-plastic instability.With the increase of phosphogypsum strength,thickness of steel tube and steel strength,the axial bearing capacity of the specimen increases.With the increase of the hollow ratio and slenderness ratio,the axial bearing capacity of the specimen decreases.(3)The force modes of HST short column,PFST short column and intermediate long columns are analyzed theoretically,and the simplified calculation formula of axial compression capacity of various components is derived.The rationality of the derived formula is verified by comparing the calculated results with the experimental results.These formulas can accurately predict the axial bearing capacity of specimens,and can provide reference for practical engineering applications.