Research On Fire Performance Of Restrained Partial Encased Concrete Columns (Strong Axis) Based On Sub-Structure Model

To investigate the fire performance of the structure,the springs are used to simulate the effect of axial and rotational restraint of the columns,and generally the spring stiffness is a constant value.Actually the stiffness of the beams linked with columns continuously decrease due to the high temperature,which results in the real restraint capability to the columns constantly changing.Therefore,there is some discrepancy with realistic condition.In order to reflect the fire resistance of the restrained PEC columns in real structure,the sub-structure contained with segmental beams,columns and slabs were employed in this paper,which can take the axial and rotational restraint into consideration and simulate the continuity of beams more accurately.Specific content as follows:1.Based on the force state and boundary conditions of PEC column under local fire condition,the sub-structure model of the PEC column is determined.2.By using the software ABAQUS,a sequentially coupled thermal-mechanical analysis model was established to calculate the axial deformation curves and fire resistance of the sub-structure including partial beams,retrained PEC columns and concrete floor slab.The model was validated by using the fire resistance test of PEC column.3.The temperature field and mechanical response analysis were conducted using the validated model of PEC column.4.The influences of the parameters such as fire load ratio,axial restraint stiffness ratio,beam-column stiffness ratio,relative slenderness and eccentricity ratio on the axial displacement curves and the axial force variation coefficient curves of the column were analyzed.5.The effects of load ratio,axial restraint ratio,relative slenderness and eccentricity ratio on the fire resistance of PEC column were studied based on the axial displacement curve.