Limbs, Concrete Filled Steel Tubular Lattice Column Experimental Research And Theoretical Analysis

At the present time,the design of laced columns mainly adopts the theory computation of the《Steel Structure Design Code. GB 50017-2003》,which simulates the concrete filled steel tubular laced columns to steel laced columns, not considering the effection of the shear,and not reflecting the great difference between the compressive strength and the tensile strength of the concrete-filled steel tubes. There is great error between the calculation result and the test result,and there is a defect in the design formula. Therefore, in-depth theoretical analysis about laced columns are needed, and the more accurate calculation theory and practical calculation formula are needed.The follow work is to aim at the problems of the design calculation about the ultimate bearing capacity of the CFST laced columns.(1) The tests about the ultimate bearing capacity and the mechanical property of the 20 axial and bias four-tube CFST laced columns whose lacing bars were arranged into K-shaped were carried out,and the differente eccentric ratio and slenderness ratio's influence on the ultimate bearing capacity and the mechanical property of the laced columns whose lacing bars were arranged into K-shaped has been obtained.(2) Considering the effection of the shear and the great difference between the compressive strength and the tensile strength of the concrete-filled steel tubes, the fiber model method of the axial four-tube CFST laced columns and the multi-phases assembling method and the fiber model method of the bias four-tube CFST laced columns have been proposed, and the corresponding computer program has been compiled.The calculation results haave been compared with the test results and the criteria results in ordor to verify the rationality of the numerical calculation method and the calculation method of the common criteria.(3) Some laced columns with differente ratio of steel,eccentric ratio,slenderness ratio,concrete strength and steel strength have been computed with the multi-phases assembling method and fiber model method in ordor to analysis influence of the differente ratio of steel,eccentric ratio,slenderness ratio,concrete strength and steel strength on the reduction coefficient of the ultimate bearing capacity of the four-tube CFST laced columns.(4) The partial stabilization analysis of the concrete-filled steel tube and the lacing bars have been carried out with the thin shell method and the thin-walled beam method. The local buckling critical loads of the concrete-filled steel tube have been deduced, and the fact that the subsequent buckling loads are only belong to the steel tubes.(5) The advantages and disadvantages of the eccentric ratio reduction coefficient and the slenderness ratio reduction coefficient about the three criteria have been analysised through comparing the the eccentric ratio reduction coefficient and the slenderness ratio reduction coefficient computing results of the existing three criteria and numeric computing and test. The concept of the equivalent slenderness ratio about the CFST laced columns has been proposed,and the simple and practical calculation formula of the ultimate bearing capacity about the laced columns has been proposed in the basis of the improved equivalent slenderness ratio.