CFST Column - Steel Concrete Composite Beam Plane Frame Fire Resistance

This paper presents theoretical analysis deeply on the behavior of steel-concrete composite structure under high temperature(fire). The main contents are listed as follows:(1) stress-stain relations of concrete at normal temperature which is suitable for using ABAQUS were proposed.Based on the result of the load-strain relations of circular concrete filled steel tubular under axial compression,this paper definded the dilatancy angle 40°.stress-stain relations of concrete under high temperature(fire) which is suitable for using ABAQUS were proposed. Based on the experimental result of circular concrete filled steel tubular under high temperature(fire), this paper definded the expression of thermo-mechanical coupled constitutive relation.(2) An accurate nonlinear finite element model of the push-out specimen has been established by ABAQUS,and the analysis results are in good agreement with the experiment results from references.Based on this, An extensive parametric study was conducted to study the the capacity and behaviour of the shear connection,then the practical formula about the ultimate shear capacity and the load-slip curve of stud connector at normal temperature were proposed.(3) Throught the establishment of ABAQUS finite element model, the load-deflection and the load-slip relations of the specimens were calculate and the analysis results are in good agreement with the experiment results from references.(4) Based on the thermal parameters of steel and concrete under high temperature(fire), an accurate nonlinear temperature field finite element model of circular concrete filled steel tubular, steel-concrete composite and the steel-concrete composite beam-CFST frame under high temperature(fire) has been established by ABAQUS to simulate the fire time-temperture curve, and the analysis results are in good agreement with the experiment results from references.Based on the stress-stain relations of concrete and steel under high temperature(fire), an accurate nonlinear finite element model of circular concrete filled steel tubular, steel-concrete composite beam and the steel-concrete composite beam-concrete filled steel tubular frame under high temperature(fire) has been established by ABAQUS to simulate the fire time-deformation curve, and the analysis results are in good agreement with the experiment results from references.(5)Based on the accurate nonlinear finite element model of the steel-concrete composite structure under high temperature(fire)established above, an extensive parametric study was conducted to study the effect of the changes of load-level, concrete strength,steel strength, steel ratio and cover thickness on the fire-resisrant of steel-concrete composite beams, the results showed that the cover thickness was the main factor on the fire-resisrant of steel-concrete composite beams. An extensive parametric study was conducted to study the effect of the changes of axial compression ratio, concrete strength,steel strength, steel ratio and cover thickness on the fire-resisrant of circular concrete filled steel tubular, the results showed that the cover thickness was the main factor on the fire-resisrant of circular concrete filled steel tubular. An extensive parametric study was conducted to study the effect of the changes of load-level, concrete strength,steel strength, steel ratio and cover thickness on the fire-resisrant of the steel-concrete composite beam-concrete filled steel tubular frame, the results showed that the cover thickness was the main factor on the fire-resisrant of steel-concrete composite beam-concrete filled steel tubular frame...