| This paper presents theoretical analysis deeply on the fire performance of multi-storey&multi-span steel-concrete composite plane frame under local fire and behavior of axially-loaded CFRP-confined concrete-filled steel tubular (CFT) stub columns. The main contents are listed as follows:(1)An thermomechanical coupling constitutive relation considering high temperature creep of steel, transient thermal strain of concrete and short-term high temperature creep along with material thermal parameters were adopted for ABAQUS to conduct fire performance and temperature field analysis of concrete-filled steel tubular columns, steel-concrete composite beams, steel-concrete composite joints and steel-concrete composite plane frames under fire;(2)A model of a multi-storey&multi-span steel-concrete composite plane frame was designed and ABAQUS was used to carry out the temperature field calculation and fire performance analysis of the model. By changing the vertical load and protective layer thickness of columns and beams, different failure modes of plane frame under local fire were discussed. Besides, the varying pattern of fire endurance of plane frame, deformation of beams and columns and internal force at bottom section of column according to fire duration under different fire conditions were analyzed;(3)Based on continuum mechanics, the mechanical models of concentric cylinders of CFRP-confined CFT columns were studied to establish the interactional elastoplastic analysis theory of CFRP, steel tube and concrete, develop an relevant nonlinear calculation program and demonstrate the working mechanism of confinement from CFRP to CFT stub columns. According to elasticplastic calculation results, the formula of the bearing capa city of CFRP-confined CFT stub columns under axial load was developed on the basis of the limit equilibrium theory. |
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