Calculation On Bearing Capacity Of CFST Column Stiffened With PBL Under Axial Load

CFST Stiffened with PBL shear connector is a new type of composite structure recentlylaunched refers to the inner wall of steel pipe vertical perforated steel plate PBL stiffener. PBLstiffener can enhance the bond strength of concrete filled steel tube interface, improve theferrule effect, prevent the steel concrete interface void and reduce the relative slip, effectivelyimprove the resistance to local buckling properties node performance and steel plate, whichmakes the RCFT with PBL stiffener has good prospect in long-span, heavy load bridge inengineering application. However, research on the RCFT with PBL stiffener is still in theprimary stage, the failure mode and the ultimate bearing capacity problems, therefore, thispaper used the model test and structural mechanics analysis and made a research oncalculation method bearing capacity of RCFT with PBL stiffener under axial load and longcolumn.Firstly, according to the principle of orthogonal test design, considering thewidth-thickness ratio, hoop coefficient, hole diameter, hole hole distance, longitudinal ribplates higher parameters influence on the bearing capacity, designed4RCFT specimens,4RCFT with longitudinal stiffeners and the15RCFT with PBL. Then, made test of bearingcapacity under axial compression, which were performed in the pressure testing machine10000kN and25000kN, get the failure mode, load-bearing capacity, and load-displacementrelationship.Secondly, collected rectangular steel pipe with steel cage, reinforced rib, binding bar,straight concrete ribbed rectangular steel tubular short columns under axial compression testat home and abroad. Analyzed the relationship between concrete strength-increasing coefficientand steel ratio, hoop coefficient, width-thickness ratio and other parameters. Results of theanalysis showed that: concrete strength-increasing coefficient of RCFT, RCFT with steel cage,reinforced rib, binding bars, longitudinal stiffener and PBL stiffener were:1.18,1.08,1.49,1.08and1.36, which proved PBL stiffener can effectively improve the bearing capacity ofRCFT.Then, by establishing mechanical model, it analyzed stress pattern of RCFT with PBL stiffener, derived formula of concrete strength-increasing coefficient, combined actual bearing capacity,made regression analysis, and got the formula of RCFT with PBL stiffener, which also were applicable inRCFT, RCFT with longitudinal stiffeners. Compared with test value, the formula of RCFT withPBL stiffener is more closer than other standard value.Finally, to compare with short column form, using the same section size and the PBLstructure, only changed the slenderness ratio of the parameters, it designed three longcolumns,which loaded in the25000kN testing machine. Test results show that RCFT withPBL stiffener has better ductility.In conclusion, research on PBL stiffened rectangular CFST short and long columnsbearing capacity calculation method has important engineering significance to the enrichmentand development of steel tube concrete structure forms of the bridge, has important theoreticalsignificance to perfect the theory of CFST structure. It discussed stability coefficient of longcolumn under axial compression, deduced calculation formula of eulor critical pressure andstability coefficient, put forward calculation formula of stability capacity, whose effect is goodcompared with test results.