Homogenous Generalized Yield Function And Ultimate Load Bearing Capacity For Rectangular Concrete-filled Steel Tubular Structures

With the advantages of simple nodes form and convenient connection,rectangular concrete-filled steel tube structure(CFST)is widely used in the engineering of trusses,and the analysis of ultimate bearing capacity is a hot topic in research field.Thus a method used in the analysis of ultimate bearing capacity and safety of structures called elastic modulus reduction method(EMRM)was proposed by our research group,combining with the current researches,then corresponding theory and application research were carried out.However,the method has not been applied to the analysis of the ultimate bearing capacity of CFST rectangular section yet.Therefore,this paper analyses the limit bearing capacity of rectangular CFST components and structures on the base of existing research.The main work and results as follows.(1)Through the analysis of axial compression,pure bending and compression-bending bearing capacity using the existing codes and books,it concluds that the calculation results of bearing capacity using DBJ/T13-51-2010 formula are in good agreement with the experimental datas and safe enough,thus the bearing capacity formula of DBJ/T should better be used to calculate the stability bearing capacity of rectangular CFST components.(2)The homogeneous generalized yield function(HGYF)is developed for CFST with different rectangular cross sections by taking full considerate of constraining coefficients.The HGYF has good accuracy,overcomes defect of the traditional generalized yield function(GYF)in analyzing the limit bearing capacity,and avoids regression analysis repeatedly by using traditional homogeneous method for GYF of different rectangular section which gets the HGYF with poor applicability and inconvenient for engineering application.(3)The elastic modulus reduction method(EMRM)is proposed for ultimate bearing capacity analysis of rectangular CFST trusses and frames.Firstly,the finite element mode is built based on the unified theory of CFST;Secondly,defining element bearing ratio(EBR)according the HGYF,and an elastic modulus reduction strategy is established on the base of principle of conservation of deformation energy,then an adaptive criterion is presented to distinguish the highly stressed elements;Lastly,the comparison of results from the proposed method with those from model experiments and incremental non-linear finite element method is performed for CFST at component level and structural one,demonstrating that the HGYF and EMRM proposed in this paper are applicative,accurate and efficient method for rectangular CFST structures.(4)The influence of axial force,shear force and bending moment on the structure is analyzed,and it is concluded that the axial force is the main control force and the impact of shear and bending moment is little.(5)The influences of parameters such as steel ratio,concrete strength,high span ratio and support position on the ultimate bearing capacity of rectangular CFST truss are analyzed,and the corresponding engineering regularity are summarized,which can provide reference for engineering design and analysis.