Research On Bearing Capacity Of Hot-rolled SHS And RHS Steel Tube Beam-column Members

In recent years,with the revolution of steel structure production technology,square and rectangular section steel tube is gradually used as the main component of the structure,and the failure mode and bearing capacity of steel members are closely related to their section parameters.At present,there are some shortcomings in the design of bearing capacity of steel members in most design codes for steel structures at home and abroad.For example,in the European Code for Design of Steel Structures,cross-sections were divided into four classes according to different aspects ratios of plates.There exists a"jumping"discontinuity in the design process of bearing capacity of section between class II and III.Meanwhile,and there was some drawbacks in Chinese design code,which neglects the interaction between plates and the stress strengthening of materials was not taken into account in codes.The continuous strength method?CSM?is a design method based on the deformation capacity of section,which can make full use of the stress strengthening properties of steel.Although CSM can effectively solve the above problems,the design theory of hot-rolled steel tube beam-column members are still poor,especially the bearing capacity of hot-rolled square and rectangular steel tube members under eccentric load needs further study.In this paper,the effects of material strength f_y,aspect ratio H/B,ratio of height-thickness h/t,width-thickness ratio b/t,eccentricity angle?and distance e,length L on the bearing capacity of beam-column members is further analyzed by using finite element method,some factors are taken into consideration such as stress strengthening and initial defects and residual stress of materials,then the limit reference values of the corresponding parameters are proposed.The results show that the normalized compressive bearing capacity N_u,FE/Af_y of beam-column members decreases with the increase of f_y.With the increased of h/t,b/t and?,the normalized capacity N_u,FE/Af_y and M_u,FE/M_pl decreased.When h/t and b/t exceed 21 and 16respectively,there is no obvious change in bearing capacity.It is suggested that 21 and 16should be taken as the limits of h/t and b/t respectively in design.With the increase of H/B,the normalized capacity M_u,FE/M_pl of uniaxial beam-column members first increases and then decreases.moreover the normalized capacity N_u,FE/Af_y gradually increases.With the increase of slenderness ratio lambda,the capacity of members increases first and then decreases,where?=19.273 is the limit slenderness ratio between local buckling and overall buckling.With the increased of eccentricity e,the normalized capacity M_u,FE/M_pl increased first and then remains unchanged,and the normalized capacity N_u,FE/Af_y decreased.On the basis of finite element analysis,the EC3-CSM design formulas for hot-rolled square and rectangular steel tube beam-column members are presented.Compared with the design formulas for hot-rolled square and rectangular steel tube bending members in Chinese codes and European and American codes,the proposed EC3-CSM formula can accurately reflect the continuous relationship between the section slenderness and the beam-column bearing capacity.The accuracy is higher when the cross-section slenderness is 0.15<?_p^—?0.68,which effectively solved the problems of the discreteness of the calculation results of the design formulas in European codes and the conservativeness of the calculation results in Chinese codes and American codes.