Research On Axial Compression And Seismic Behavior Of Composite Columns With Concrete Filled Steel Tube Flanges And Honeycombed Steel Webs

With the development of building system to large span,heavy load and ultra-high height,the traditional steel structure system has poor stability and is prone to buckling deformation,resulting in structural instability and damage,therefore,the steel structure system is not well adapted to the super-high,heavy-duty and large-span building system.Therefore,to meet the requirements of building structure,structures or components with good seismic and fire resistance will be more suitable for the development need of the current building structure.Concrete filled steel tube column is an innovative composite structure,which is widely used in high-rise buildings and bridge piers due to its high section modulus,high strength,and good seismic performance.So far,all over 300m of the high-rise buildings in China are steel-concrete composite structures.On the basis of the current development situation,our research group proposed for the first time an evolution of the steel frame structure,that is,a new fabricated composite frame system with rectangular concrete flange honeycomb steel webs H-shaped（or cross shaped）composite columns as frame columns and rectangular concrete flange honeycomb steel webs I-shaped composite beams as frame beams,which realizes the stable connection of composite beams and columns through integral nodes.This system is suitable for new large-span buildings,super-high buildings and the transformation of existing buildings.The main research work of this paper is as follows:1.The reasonable constitutive model of steel and concrete were selected,and 14 finite element models of the test specimens were established by ABAQUS,the load-displacement curves and the failure forms of the specimens were obtained,and the correctness of the finite element model was verified by the results from the FEM analyses compared with the experimental results.2.In order to study the axial compression behavior of composite stub columns with concrete filled steel tube flanges and honeycombed steel webs（STHCC）,the constraint effect coefficient（ξ）,steel stub strength grade(f_yfk),concrete strength grade(f_ck),slenderness ratio（λ）,pitch-height ratio（s/h_w）and hole-height ratio（d/h_w）are the control parameters,and 12groups of further expand 36 STHCC composite stub columns were designed,the influence of different parameters of further expand 36 STHCC composite stub columns were investigated,and their failure modes,stress-strain relationship and stress mechanism of steel and concrete were analyzed.Finally,the reasonable matching suggestion of concrete-filled steel tube flanges and honeycombed steel web was given,and the axial compression bearing capacity reduction coefficientβwas introduced,and the 1st Opt software was used to statistically regress the axial compression bearing capacity calculation formula of STHCC composite columns.3.With steel stub strength grade(f_yfk),concrete strength grade(f_ck),shear span ratio（λ_s）,the height-to-width ratio（D/B）,section steel content（α）,axial compression ratio（n）are the control parameters,the seismic performance of 22 STHCC composite columns were investigated,and effects of different parameters on hysteresis performance,energy dissipation capacity,resistance attenuation,stiffness degradation,skeleton curve and ductility of STHCC composite columns were studied.The results show that the seismic capacity of the specimen is greatly affected by the axial compression ratio（n）,section steel content（α）and the height-to-width ratio（D/B）.The hysteresis curve of the specimens with smaller axial compression ratio,the smaller height-to-width ratio and the the high section steel content showed a fuller shuttle,slower stiffness degradation,larger ductility coefficient,and superior seismic performance.When the axial compression ratio remains the same,within a certain range,increasing the yield strength of the steel tube can effectively increase the energy consumption and the rate of stiffness degradation,meanwhile,can improve the ductility and deformation ability of the specimens.Finally,the design suggestion of the composite columns under earthquake action was given,and it was suggested to be popularized and applied in practical engineering.