| With the wide application of composite structures such as concrete-filled steel tubular(CFST)structures in super high-rise buildings,it is imperative to study the disaster prevention performance of new composite components.In the whole life cycle of structure,it may suffer disasters such as fire,impact and explosion,etc.When the key vertical members of structure are failed,the remaining structure may suffer progressive collapse.As the key component of system,the beam-column joint plays an important role in the process.In this paper,the resistance to progressive collapse of the circular CFST column-steel beam joint with outer-ring plate and the square CFST column-steel beam joint with through bolt-extended endplate are studied.The main research works which have been done are listed as follows:(1).For the circular CFST column-steel beam joint with outer-ring plate,the finite element(FE)method is used to verify the test of the research group and related tests in China and abroad.Meanwhile,FE analysis of the resistance to progressive collapse of the experimental joint is carried out.The resistance mechanism,failure mode,stress and strain development of crosssection of joint under progressive collapse condition.And the effects of constructions of outerring plates,material properties and geometric parameters on the resistance to progressive collapse of joints are analyzed.(2).The monotonic loading test of CFST column-steel beam joints with through boltextended endplate under progressive collapsed is carried out to investigate the overall deformation,failure mode,resistance to progressive collapse and strain development of critical section.The FE model of the square CFST column-steel beam joint with through bolt-extended endplate is established.In this FE model,the method of bolt pretightening force is discussed.Meanwhile,the failure mode,stress at core area and resistance mechanism of joint are analyzed.(3).In order to further analyze the failure mode and deformation process of the square CFST column-steel beam joint with through bolt-extended endplate,the FE method and constitutive selection of joints are considered in detail.The method by using ABAQUS/Explicit module to analyze the anti-progressive collapse performance of joint is proposed.The techniques such as smooth step loading criterion and controlled kinetic energy model are used to guarantee that the static loading and contact relationship are reasonable and effective.The steel constitutive such as steel plate and through bolt for ABAQUS/Explicit module is proposed.The reasonable constitutive model of steel plate and through bolt materials under large deformation are selected,and the comprehensive fracture criterion and damage evolution path of ductile damage,shear damage and mixed damage modes based on stress triaxiality are considered in the steel constitutive structure,respectively.(4).For the square CFST column-steel beam joint with through bolt-extended endplate,the influence of strength and weak relationship of through-bolt,extended endplate and steel beam on the resistance to progressive collapse of joint is considered.Five FE models with two sets of different key component characteristics are designed and established.The influence of key component characteristic on the failure mode and resistance mechanism of joint under progressive collapse condition is investigated.And the deformation process,fracture evolution process and stress development process of through bolt,extended endplate and steel beam are analyzed. |
