Study On Biaxial Bias Loading Behavior Of Corroded RACFST Slender Columns

Recycled aggregate concrete(RAC)technology reduces the demand for natural aggregate,plays an active role in recycling concrete,reducing the damage of construction waste to the environment.and is of great significance to the protection of the environment and the sustainable development.It is of great significance to protect environmental and achieve sustainable development.However,there is still a gap between the mechanical properties of RAC and natural aggregate concrete,which limits the application and promotion of RAC technology.The recycled aggregate concrete filled steel tube(RACFST)structure is composed of steel tube and RAC,which optimizes the mechanical properties of RAC and gives full play to the advantages of steel tube and RAC.At present,there are many studies on RACFST slender columns,but the bearing performance of corroded RACFST slender columns needs further research.Considering that the columns in practical engineering are mostly subjected to biaxial eccentric compression load,this paper carries out biaxial eccentric compression tests on seven corroded RACFST slender columns.Based on the test,the finite element simulation and theoretical analysis are carried out to study the influence of different parameters on the bearing capacity of the corroded RACFST slender columns.The conclusion is as follows:(1)When the specimen under the biaxial eccentric compression reaches the yield load,it will go through a long period of plastic development to achieve the state of damage.While specimen under the axial compression reaches the peak load,the bearing capacity will decline rapidly.The specimen with larger eccentricity has smaller peak stiffness and larger displacement corresponding to yield load.The specimen with smaller eccentricity has faster stiffness degradation.The change of eccentricity angle has no significant effect on the displacement corresponding to yield load.(2)The safety reserve coefficient of specimen under axial compression is smaller than that of specimen under biaxial eccentric compression,indicating that the specimen under axial compression has higher strength reserve.The ductility of specimen under biaxial eccentric compression is greater than that of specimen under axial compression,indicating that the plastic deformation ability of specimen under biaxial eccentric compression is better.(3)The increase of corrosion degree will reduce the initial stiffness and peak bearing capacity;The change of RAC strength will not change the failure mode of RACFST column,but the bearing capacity and initial stiffness will decrease with the decrease of RAC strength.The increase of steel strength will increase the bearing capacity,initial stiffness and the displacement corresponding to the peak bearing capacity.(4)There is a limit corrosion degree ?.When the corrosion is less than ?,the bearing capacity of RACFST columns decreases slowly;once the corrosion degree is greater than ?,the bearing capacity of RACFST columns will decline rapidly.(5)Based on the unified strength theory and considering the influence of corrosion,the calculation formula of biaxial eccentric bearing capacity of RACFST slender columns is derived.The results of the formula are in good agreement with the experimental results,which verifies the applicability and reliability of the formula.