Endurance Test Research Of Steel Reinforced Concrete T-shaped Column Under High Temperature

The steel concrete special-shaped column is that the structure of vertical component configuration and the corresponding steel stirrups in reinforced concrete special-shaped column.As a new type of structure,it has the advantages of high bearing capacity,flexible layout,good anti-seismic performance and has been widely applied,but it is easy to damage in the fire because of its high percentage of steel and large fire face.At the same time,at home and abroad,there are few experimental researches on the steel reinforced concrete special-shaped column in the fire,especially the T section.This paper describes that 8 steel reinforced concrete T shaped columns was designed and casted.They were studied under high temperature and analyzed axial compression ratio,eccentricity,loading angle,spacing of stirrups and steel ratio of steel reinforced concrete T shaped column failure,temperature field characteristics and effects of the fire resistance limit and draw the following conclusions.(1)?In axial compression,the wing flange of steel reinforced concrete special-shaped columns were severely damaged and cracks are vertical cracks or a small number of diagonal cracks;In eccentric compression,when the eccentricity is large,there are huge number of diagonal cracks on the eccentricity direction and there are some horizontal cracks on the opposite of loading point.(2)?The temperature of the cross-section of the location of the same temperature,the first30 min temperature is slow,then enter the short temperature platform,the duration of about 10~ 20 min,the platform area temperature measurement points are different,but are in the range of 100 ~ 150 ?,And the more close to the central area of the phenomenon of the more obvious platform after the temperature was parabolic rise.In the axial compression,with the increase of axial compression ratio,T column internal heating rate is higher;the warming trend of sections of each position is roughly the same;the temperature along the axis outward circular symmetry;in eccentric compression,along the direction of eccentricity has quick heating temperature.(3)? In the process of heating under constant load,the axial displacement of steel reinforced concrete T shaped column roughly the same changed trend;it has less changesbefore 40 min,and then,axial displacement rise up to the highest point;after increasing,it appears linear decrease approximately.The range of rising displacement and time decrease gradually with the increasing of the axial compression radio and eccentricity.Even in a certain axial compression ratio and eccentricity,axial displacement does not appear to rise and decline phenomenon directly.(4)? With the increase of axial compression ratio and eccentricity,the limit of fire resistance decreases gradually;in the eccentric compression,loading point is in the strong axis;fire endurance is larger;the fire endurance at 45 degrees direction and on the weak axis is smaller.Spacing of stirrups has little influence on the fire resistance limit;Under the premise of meeting the requirements of the structure,the distance between the ribs increases and the fire resistance decreases slightly.With the increase of the steel ratio,the fire resistance limit increase obviously,and the fire resistance limit is nearly doubled when the steel ratio is increased by 15%.(5)? The influence of all factors on the fire resistance of steel reinforced T shaped concrete columns were studied.The effect of the ratio of steel to steel is the largest and the influence of axial compression ratio,eccentricity and loading angle is the second and the least influence of the space of web reinforcement.