Experimental study on CFST stub columns strengthened with outer steel tube and sandwiched concrete jackets under axial compression
Concrete-filled steel tube(CFST)structures may be in urgent needs of strengthening and renovation due to physical aging,chemical erosion,extreme disaster and other factors during service,or changes in their functional use.To this end,a strengthening technology using outer steel tube and sandwiched concrete jackets to strengthen concrete-filled steel tube(CFST)columns is proposed in this study.Ten strengthened columns(including five strengthened columns with inner circular and outer circular section and five strengthened columns with inner square and outer square section)and two un-strengthened CFST columns were tested under axial compression.Based on the analyses of the failure modes,load-displacement curves,relative load-strain curves,and composed compressive strength,the effects of the cross-section form(square and circular section),thickness of outer steel tube(2.5～5.5 mm),and sandwiched concrete strength(C50～C70)on the axial compressive behavior of the combined strengthened columns were investigated.The results show that the local buckling degree of the original CFST columns is reduced after strengthening owing to the presence of the outer steel tube and sandwiched concrete,and the axial stiffness and compressive capacity is greatly improved.The average increase of bearing capacity of circular concrete-filled steel tube and square concrete-filled steel tube column is 151％and 212％,respectively.The load-bearing capacity of the combined strengthened columns increases with the thickness of the outer steel tube and the strength of the sandwiched concrete.The composed compressive strength of circular-section strengthened stub columns is higher than that of square-section columns,and the influence of the outer steel tube thickness on the composed compressive strength of circular-section columns is more significant than that of sandwiched concrete strength.The limit equilibrium method was used to calculate the force state and longitudinal stress of each component of the circular-section and square-section retrofitted stub columns.A calculation formula of axial compressive bearing capacity of the combined retrofitted stub columns was proposed,and the calculation results fitted well with the test results,indicating that the proposed formula can be used to calculate the bearing capacity of the composite strengthened columns.
万方数据
维普
