| Currently,steel construction has been universal used in practical projects.Steel construction has many merits for instance light conduct oneself with dignity and fine overall stability,but its shortcomings cannot be ignored,that is,poor high temperature resistance.In many studies at home and abroad,most of the steel notes are studied under the impact of axial force,bending moment and both without heat influence.In this paper,a certain temperature is applied to the heat-affected zone of KT steel joints.The impact of axial force and bending moment the mechanical behavior of nodes are founded using ABAQUS finite element method.Under the impact of heat,taking into consideration the impact of changes in individual parameters on the finlly capacity of the joint,the general law is found out.Finally,the orthogonal test method is used to fit the formula under the bending capacity of the joint.The conclusions obtained are as follows:(1)Under the action of axial force alone,the ultimate bearing capacity of joints in the presence of heat is significantly lower than that the lack of heat,which is mainly related to the composition of the steel body.The internal crystal structure of the steel is very sensitive to temperature.Besides,the thermal conductivity of the steel is large,the thermal conductivity is fast,the plastic deformation develops rapidly under high temperature,and the strength will also decrease.The same is true when the bending moment acts alone.(2)Under the action of axial force alone,based on the thermal influence,considering the influence of five parameters on the mechanical behavior of the node,for example the width thickness rate of main pipe γ,width rate of additional pipe to main pipe β,angle between branches and main pipes θ,wall thickness rate of additional pipe to main pipe τ and the gauge H of the web plate.The conclusion is that the larger the values of γ and θ,the smaller the limit bearing capacity of the note;The larger the values of β,τ and H,the greater the limit bearing capacity of the note;when 20≤γ≤30,0.5≤β≤0.6,0.5≤τ≤0.75,30°≤θ≤45°,the effect of increasing the bearing capacity of joints under axial action is more obvious.(3)Under the action of bending moment alone,based on the thermal influence,considering the influence of five parameters on the mechanical behavior of the node,for example the width thickness rate of main pipe γ,width rate of additional pipe to main pipe β,angle between branches and main pipes θ,wall thickness rate of additional pipe to main pipe τ and the gauge H of the web plate.The conclusion is that the larger the values of γ and θ,the smaller the limit bearing capacity of the note;The larger the values of β and H,the greater the limit bearing capacity of the note;τ Little impact on ultimate bearing capacity of joints.When 10≤γ≤20,0.5≤β≤0.6,30°≤θ≤45°,40≤H≤50,the effect of increasing the bearing capacity of joints under bending moment alone is more obvious.(4)Under the action of bending moment alone,the formulas between each parameter and ultimate bearing capacity are fitted on the basis of heat influence.Finally,representative joint conditions are selected through orthogonal test method,and the formula for the bearing capacity of KT notes under thermal conditions,which provides reference for future research. |
