Research On Axial Compression And Seismic Performance Of GFRP Tube Reactive Powder Concrete Composite Columns With Encased Steel

The compressive strength of reactive powder concrete is higher than that of ordinary concrete,and has GFRP excellent hoop tensile strength.Combining the reactive powder concrete and GFRP can make the best of the behavior of the material.Based on this,this study proposes GFRP tube reactive powder concrete composite columns with encased steel which is set inside.The encased steel is beneficial to prevent the composite column from shearing damage and ensure the stable behavior of the composite column.It can be seen that this type of composite columns has high bearing capacity,good durability,strong deformation ability and good seismic behavior,for which it can be widely used in the actual frame structure system.In order to study the axial compression performance of the GFRP tube reactive powder concrete composite short columns with encased steel（GRS）,25 GFRP tube reactive powder concrete composite short columns with encased steel are designed by considering the diameter of the GFRP tube（D）,the thickness of the GFRP tube（t）,the number of fiber winding layers（n）,and the fiber winding angle（θ）,the slenderness ratio（λ）,the compressive strength of reactive powder concrete（f_c）,the area of encased steel（A_s）the strength of encased steel(f_sy).Based on the existing theoretical results,a verification analysis was carried out on14 existing specimens with similar structures,and the maximum error was within 2.22%.The two were in good agreement,which verified the rationality of the finite element modeling method.Based on this,a total of 25 GFRP tube reactive powder concrete composite columns with encased steel were carried out finite element numerical analysis in this paper,the axial load-displacement curves and failure characteristics of the composite columns were obtained,and the effect of different parameters on the axial compression bearing capacity and ultimate displacement of the specimens were investigated.The results show that,the axial compression bearing capacity of GFRP tube reactive powder concrete composite columns with encased steel columns increases significantly by increasing of the diameter of the GFRP tube,the thickness of the GFRP tube,the number of fiber winding layers,the fiber winding angle,the strength of encased steel,the compressive strength of reactive powder concrete and the area of encased steel.With the increase of the thickness of the GFRP tube,the number of fiber winding layers,the angle of fiber winding,the slenderness ratio of the specimen,and the cross-sectional area of??the I-shaped steel,the ultimate displacement of the specimen increases significantly.But as the diameter of the GFRP tube increases,the ultimate displacement of the composite columns gradually decreases.A good load-holding capacity and ductility is showed by all the specimens within the parameter range of this paper.Finally,based on the force mechanism of the composite column,the constraint effect coefficient（?）of the GFRP tube is introduced,and the calculation formula for the axial compression bearing capacity of the GRS composite short column is statistically regressed using by software named of 1st Opt.Based on the analysis of the axial compression performance of the GFRP tube reactive powder concrete composite columns with encased steel,A numerical analysis of the seismic performance of 17 GFRP tube reactive powder concrete composite columns with encased steel under low-cycle reciprocating loads has been carried out by considering the diameter of GFRP tube（D）,the thickness of the GFRP tube（t）,the number of fiber winding layers（n）,and the fiber winding angle（θ）,the axial compression ratio（n₀）,the compressive strength of reactive powder concrete（f_c）,the area of encased steel（A_s）the strength of encased steel(f_sy).The horizontal load-displacement curve drawn,failure characteristics and stress distribution cloud diagram were obtained of each specimen.The influence of the hysteretic performance,skeleton curve,energy dissipation capacity,resistance attenuation and stiffness degradation of GRS composite columns were studied.The results show that the axial compression ratio and the restraint effect provided by the GFRP tube have a significant impact on the seismic performance of the GFRP tube reactive powder concrete composite columns with encased steel.Suggestions for the seismic design of the composite column are given within the parameter range of this article.The foundation for the application of this kind of composite column was laid in actual engineering.