四周受火异形截面部分包覆钢-混凝土轴压组合柱耐火性能试验研究OA北大核心CSTPCD

Special-shaped partially encased composite steel and concrete(PEC)columns is one of the effective solutions to solve the convex column problem of high-rise steel residential buildings.Due to the exposed steel flanges,its fire resistance has attracted much attention.In order to explore the fire resistance of special-shaped PEC columns,four special-shaped PEC columns were designed and fabricated with different cross-section shapes and axial compression ratios,and the fire tests with constant axial load were carried out.The failure mode,vertical and lateral deformation-time curves and fire resistance of special-shaped PEC columns under fire were obtained,and the temperature field distribution and deformation modes were analyzed.The results show that with the damage evolution under fire,L-shaped and T-shaped PEC columns gradually change from axial compression to bidirectional and unidirectional eccentric compression,respectively,while the cross-shaped PEC columns still maintain axial compression.Under the boundary conditions of the upper spherical hinge and the lower unidirectional hinge,the L-shaped PEC column fails in the bidirectional flexural buckling,the T-shaped PEC column fails in the out-of-plane flexural buckling,and the cross-shaped PEC column fails in the in-plane flexural buckling.Under the axial compression ratio of 0.4,the fire resistance of L-shaped PEC column without fire protection reaches 41 min,the fire resistances of T-shaped and cross-shaped PEC columns are 32.5 min and 29 min,respectively.When the axial compression ratio increases from 0.4 to 0.55,the fire resistance of the cross-shaped PEC column decreases by 28.7％.It is found that the simplified bearing capacity calculation method of regular cross-section PEC columns subjected to fire on all sides recommended in EN 1994-1-2 is conservative to predict the bearing capacity of special-shaped PEC columns at fire resistance.