Study On Fire Resistance Of Recycled Aggregate Concrete-Filled Rectangular Steel Tube Columns Under Eccentric Loading

In order to effectively treat and use waste concrete,recycled aggregate concrete(RAC)technology emerges as the times require.RAC has some shortcomings such as low strength and low modulus of elasticity,but recycled aggregate concrete filled steel tube can effectively avoid these shortcomings.Relative to recycled aggregate concrete filled circular steel tube,recycled aggregate concrete filled rectangular steel tube(RACFRST)is convenient connection with beams connection and convenient for decoration.Many scholars have conducted relevant research on its mechanical properties.However,people still lack the necessary understanding of the fire resistance of RACFRST.In this paper,experimental study and finite element analysis on fire resistance of RACFRST columns under eccentric loading were carried out.Main tasks are as follows:(1)Three RACFRST columns subjected to eccentric load and one RACFRST column subjected to axial load were designed and tested for fire resistance.Two main influence factors including replacement ratio of recycled coarse aggregate and eccentricity were considered.The temperature field distribution of cross-section,axial displacement curve,failure mode and fire resistance limit of the specimens has been obtained.Considering the influence of replacement ratio of recycled coarse aggregate and eccentricity on fire resistance of RACFRST columns.(2)RACFRST columns were modeled to do fire-structure coupling analysis using ABAQUS.The temperature field distribution of cross-section,the axial displacement curve,lateral displacement curve and fire resistance limit were obtained,and the model was validated using some experimental test data.(3)The finite element analysis model was then used to investigate the influence of material parameters,steel ratio,eccentricity ratio,slenderness ratio,replacement ratios,load ratio,aspect ratio and perimeter on the axial displacement curve and fire resistance limit of RACFRST columns under eccentric loading.And a simplified formula for calculating the fire resistance limit of RACFRST was proposed.