Experimental Research On Seismic Performance Of L-special-shaped Steel Reinforced Concrete Columns After Fire

Steel reinforced concrete special-shaped columns are developed on the basis of shaped RC columns and steel reinforced concrete structures.Due to the steel,its bearing capacity,stiffness,ductility and seismic performance have been significantly improved.However,the fire will have a significant impact on the seismic performance of SRC columns.internal channel steel will accelerate the conduction of temperature to make severe damage.In this paper,the seismic behavior of L-shaped SRC columns after fire is studied,which provides basis for the damage assessment and design theory of SRC structures after fire.The main content:(1)L-shaped SRC columns are designed by axial compression ratio,shear span ratio and spacing of web member.Fire test has a damage standard which is the time when temperature of concrete which is 20 mm far from the heated side reached up to 400 ℃.(2)Based on the experiment of 8 steel reinforced concrete columns subjected to low cyclic reversed lateral loads,the main failure patterns of steel reinforced concrete columns are obtained,and the influence of fire,axial compression ratio,shear span ratio and web spacing on the bearing capacity,ductility,rigidity and energy dissipation capacity of steel reinforced concrete columns are analyzed.The main conclusions:(1)The hysteresis curve of the specimen is plumper and symmetrical about the origin.L-shaped steel reinforced concrete columns after fire still have a good seismic performance.(2)The main failure patterns of steel reinforced concrete columns include shear type and flexure-shear type.The specimen in room temperature produces shearing failure,and the burned specimen is subjected to bending shear failure.There was a transition of the failure mode from shear-bending failure to shear failure along with the increasing of axial compression ratio.The shear stress decreased with the increase of the shear-span ratio,and the failure mode changed from shear failure to bending shear failure,with the spacing of webs increases,failure mode changed from bending shear failure to shear failure.(3)Fire has little effect on the rigidity,ultimate bearing capacity,ductility and energy dissipation capacity of L-shaped SRC columns.The ductility decreased with fire effect.The rigidity and ultimate bearing capacity of L-shaped SRC columns increased with the increased of axial compression ratio and the deformation behavior becomes worse.The ductility,yield load and ultimate bearing capacity decreases with the increase of the shear span ratio.The rigidity and bearing capacity including yield load and ultimate bearing capacity decrease with the increase of the spacing of web members.The ductility becomes worse due to the dense arrangement of the webs,which limits the deformation ability of channel steel.(4)For the L-shaped steel reinforced concrete columns subjected to fire,The strain measurement proves that the average strains agree with the assumption of plane section.(5)In this test,the neutral axis of the L-shaped steel-reinforced concrete column is perpendicular to the loading direction.