Research On Mechanical Behavior Of Concrete Filled Square Steel Tube Columns With Inner I-shaped Profiled CFRP Under Lateral Impact Load

Concrete-filled steel tubular(CFST)composite structure is widely used in civil buildings,bridge structures and underground engineering fields bacause of its high bearing capacity,good toughness,easy construction,fire and corrosion resistance and good economic benefits.Carbon Fibre-reinforced Polymer(CFRP)has been developed and applied to modern structures because of its high tensile strength,light weight and easy molding.Place I-shaped CFRP inner with CFST columns not only can reduce the section size,lighten the self weight and increase the service area but also effectively enhance the resistance of composite columns to lateral impact load.Structures might be crashed by lateral impact loads during service,which may bring local damage to members or even permanent deformation and loss of bearing capacity occur.Either way happens,it is a kind of loss to people’s life and property.Therefore,the study of impact resistance is one of the key research issues in the field of engineering at home and abroad.Besides the characteristics of short impact time,large energy release and rapid deformation,impact process also has some others problems,such as the consumption of impact energy under dynamic condition is quite different from static’s,the complex coupling effect of axial load and lateral impact load,and the failure of each component is difficult to determine.The existence of the above conditions brings great difficulties to the study of the mechanical mechanism of impact resistant components.Therefore,It’s of great significance to research on mechanical behavior of concrete filled square steel tube columns with inner I-shaped profiled CFRP under lateral impact load.Based on the accurate constitutive model and contact relationship of steel tube,concrete and CFRP,considering the strain rate effect of materials under dynamic condition,using the ductile damage model of steel tube and Hashin failure criterion of CFRP to define the failure conditions of the two materials,nonlinear finite element analysis(FEA)software ABAQUS was used to simulate 17 square concrete-filled steel tube columns with inner I-shaped CFRP under the lateral impact.The impact force versus time curves and mid-span displacement versus time curves of typical members were analyzed,and the whole process analysis of its working mechanism was also carried out.Stress-strain curves and the failure of each material in different stages were studied.The results showed that the impact process could be divided into three stages: the peak stage,the platform stage and the descending stage.Plastic deformation and impact energy consumption of the components were fully developed in the platform stage.So the platform value reflected the ability of lateral impact resistance.Taking ordinary CFST components as comparative studies,the influence of the inner CFRP profile on the impact resistance of the component was analyzed.According to the results,CFRP profiles could improve the lateral impact resistance of component by 24%.The ductility could be increased by increasing the size of CFRP,while the effect wouldn’t improve all the time,so the best section configuration ratio was 9.16% to resist the lateral impact.Due to the coupling effect of axial load and lateral load,when the axial compression ratio was less than 0.5,the existence of axial force had a favorable effect on the lateral impact resistance of the components,and when the axial compression ratio was greater than 0.5,the effect was opposite.