| Prefabricated steel building is an important representative of green building.The seismic performance of special-shaped concrete-filled steel tubular(SS-CFST)column structure is excellent,which can solve the problem of convex column edges in residential buildings.At present,it has become an important structural form of prefabricated steel residential buildings.However,the existing SS-CFST column structure still has the problems of large welding workload and high requirements for processing and manufacturing accuracy.Due to the existence of special-shaped column section,the joint has significant spatial coupling stress characteristics under earthquake.The existing research of SS-CFST column can not meet the needs of practical engineering.Therefore,this thesis proposes a hoop-type SS-CFST composite column which is convenient for rapid assembly and its corresponding hooped reinforced beam column connection joint.The mechanical properties and design methods of the above structure are studied by using the methods of experimental research,numerical simulation and theoretical analysis.The main contents are as follows:(1)The axial compression performance tests of four hoop-type and four weld-type SSCFST columns were carried out,and the effects of section form,steel tube wall thickness and slenderness ratio on the failure mode and bearing capacity were analyzed.The results show that the failure modes of SS-CFST columns under axial compression are mainly local buckling failure of steel tube and overall bending instability failure of specimens;The ultimate bearing capacity of hoop-type specimens SL-1,ST-1 and SL-2 is 19.86%,20.86% and 20.00% higher than that of weld-type specimens WL-1,WT-1 and wl-2 respectively.Hoop can not only be used as a connecting component between square steel tubes to coordinate deformation and work together,but also enhance the restraint effect of steel tubes on core concrete,make the steel tubes bulge locally in a wider range,and improve the bearing capacity and ductility of specimens.(2)The calculation method of bearing capacity of SS-CFST columns is established.Considering the restraint and reinforcement effect of the steel tube coincidence area and the hoop connection part on the core concrete,the relevant constrained concrete constitutive relationship model is modified,and the axial compression numerical analysis model of SS-CFST column is established by using this model.On the basis of verifying the accuracy of the model,the influence laws of steel tube wall thickness,steel strength,concrete strength and hoop structure on the axial compression bearing capacity of the specimen are analyzed,The bearing mechanism of SS-CFST columns under axial compression is revealed,and the calculation method of bearing capacity of SS-CFST column is established by using the unified theory.The results show that the average value of the ratio of the axial compression bearing capacity of each specimen calculated by the finite element model to the test results is 1.011 and the mean square deviation is 0.069.The finite element model has good accuracy;The thickness of steel tube,the strength of steel tube,the strength of concrete and the slenderness ratio are the main factors affecting the bearing capacity of axial compression;The error between the calculation results of the bearing capacity formula proposed in this thesis and the experimental and numerical simulation results is less than 15%,which is in good agreement.(3)The seismic performance tests of 9 SS-CFST column-H-shaped steel beam hoop strengthened joints were carried out.The quasi-static tests of three plane cross joints and six spatial corner joints are carried out by using the beam end loading method.The failure mode,hysteretic curve,skeleton curve,strength degradation,stiffness degradation,ductility,energy dissipation capacity and strain distribution are analyzed.The effects of side plate thickness,side plate height and side plate connection length on the seismic performance of the joint are studied.The results show that the failure modes of joints mainly include side plate fracture failure,beam flange tear failure and beam end plastic hinge failure;The failure mode of the joint is related to the component size.The bearing capacity of the side plate fracture failure joint is low and the ductility is poor.The hysteretic curve is in a narrow shuttle shape,and the energy consumption capacity of the joint has not been brought into full play.The bearing capacity of the beam end failure joint is high and the ductility is good.The hysteretic curve is in a full shuttle shape and has good energy consumption capacity.(4)The design method of hoop reinforced joint between SS-CFST column and H-shaped steel beam is proposed.The refined finite element model of the joint considering geometric nonlinearity and material nonlinearity is established,the stress development process of each component of the joint in the loading process is analyzed,the force transmission path of the joint and the core area is revealed,the effects of geometric parameters,physical parameters and load parameters on the flexural capacity and initial stiffness of the joint are studied,and the calculation formula of the flexural capacity of the joint is proposed based on the yield line theory.The results show that the failure mode,hysteretic curve,skeleton curve and bearing capacity of each specimen are in good agreement with the experimental results;There is stress concentration at the junction of side plate and hoop and at the connecting corner between side plate and beam flange;The thickness and height of side plate,the width thickness ratio of square steel tube and the yield strength of steel have a great influence on the bearing capacity of the joint.The length of side plate connection has no obvious influence on the bearing capacity of the joint,but has a great influence on the initial stiffness of the joint.The error between the calculation formula of joint bearing capacity proposed in this thesis and the experimental and numerical simulation results is within 10%. |
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