Fire performance of restrained PEC columns under axial load based on sub-structure model

By using the software ABAQUS,a finite element model was established to calculate the temp erature field and mechanical behavior of the sub-structures including partial beams and retrained PEC columns,then the model was verified by fire test data.The verified model was used to analysis the behavior of the sub-structure subjected to axial load under fire condition,including influence of axial load ratio,axial restraint stiffness,retrained beam span,column length and materials strength on the axial displacement and the axial force.It can be seen from the research results that the axial displacement and the axial force enhancement coefficient decrease due to an increase of the axial load ratio.The increasing of axial restraint stiffness lead to a higher peak value of the enhancement coefficient and lower axial displacement,then the axial displacement reduce gently when the column is compressed.The augment of column length induces a slightly increase in the axial displacement and the axial force enhancement coefficient,while the retrained beam span,steel yield strength,concrete compression strength have little influence.