Study On Eccentric Compressive Behavior Of Concrete-filled Steel Tubular Columns Filled With Steel Parts

Through the fire resistance test and axial compression test,it is found that under the condition that the total steel consumption is almost unchanged,the fire endurance of steel tubular column filled as thinning steel wall with high-strength steel angles or stirrups can be remarkably increased,and the axial compressive performance of such columns changes little compared with the traditional CFST(Concrete Filled Steel Tube)column.However,it is worrying whether the steel wall thinning will weaken the eccentric performance of the column obviously.In response to this concern,the eccentric performance of concrete-filled steel tubular columns with highstrength steel angles or stirrups is studied in this paper.The specific work is as follows:1.Eight square steel tubular columns filled with high-strength steel angles and two traditional square CFST columns were tested under eccentric compression and the influences of ratio of steel angles weight to total steel weight,clear distance between the steel angle and steel tube and eccentricity have been investigated.It is found that:(1)under the condition that the total steel consumption is almost unchanged,when the clear distance between the steel angle and steel tube is 10 mm or 30 mm,eccentric load bearing capacity of square steel tubular columns filled with high-strength steel angles increases by 2.7%?14.9% and decreases by 2.7%?12.9% respectively compared with the traditional square CFST columns,while such column's equivalent stiffness and ductility change little.In practical engineering,eccentric load bearing capacity of square steel tubular columns filled with high-strength steel angles can be the same as that of traditional square CFST columns by reasonable design of ratio of steel angles weight to total steel weight and clear distance between the steel angle and steel tube;(2)Compared with ratio of steel angles weight to total steel weight,clear distance between the steel angle and steel tube has a more obvious effect on the eccentric load bearing capacity of square steel tubular columns filled with high-strength steel angles.2.Eight square steel tubular columns filled with stirrups and two traditional square CFST columns were tested under eccentric compression and the influences of ratio of stirrups weight to total steel weight,clear distance between stirrups and steel tube and eccentricity have been investigated.It is found that:(1)under the condition that the total steel consumption is almost unchanged,when the eccentricity is 60 mm,eccentric load bearing capacity of square steel tubular columns filled with stirrups change little,compared with the traditional square CFST columns.However,when the eccentricity is 120 mm,the former column's eccentric load bearing capacity will be reduced by 10.1%?15.5%;(2)When the eccentricity is relatively small,compared with ratio of stirrups weight to total steel weight,clear distance between stirrups and steel tube has a more obvious effect on the eccentric load bearing capacity of square steel tubular columns filled with stirrups;When the eccentricity is relatively large,ratio of stirrups weight to total steel weight and clear distance between stirrups and steel tube nearly have the same effect on the eccentric load bearing capacity of such columns;(3)Compared with traditional square CFST columns,the equivalent stiffness of square steel tubular columns filled with stirrups changes little while the ductility coefficient of such columns is greatly improved.3.Eight circle steel tubular columns filled with stirrups and two traditional circle CFST columns were tested under eccentric compression and the influences of ratio of stirrups weight to total steel weight,clear distance between stirrups and steel tube and eccentricity have been investigated.It is found that:(1)under the condition that the total steel consumption is almost unchanged,when the eccentricity is 60 mm,eccentric load bearing capacity of square steel tubular columns filled with stirrups changes little or increases slightly,compared with the traditional circle CFST columns.However,when the eccentricity is 120 mm,the former column's eccentric load bearing capacity will be reduced by 5.4%?13.8%;(2)With the increase of ratio of stirrups weight to total steel weight or clear distance between stirrups and steel tube,eccentric load bearing capacity of such column decreases on the whole;(3)Compared with traditional circle CFST columns,the equivalent stiffness or ductility of circle steel tubular columns filled with stirrups changes little or increases slightly;It is also found that:(1)under the same condition of other factors,the eccentric load bearing capacity of the square CFST column with high-strength steel angles is mostly higher than that of the square CFST column with stirrus,but the descending section of load–mid-height deflection curves of the former is steeper than that of the latter;(2)In practical engineering,when the eccentricity is relatively small,eccentric load bearing capacity of circle or square steel tubular columns filled with stirrups can be the same as that of traditional circle or square CFST columns by reasonable design of ratio of steel angles weight to total steel weight and clear distance between the stirrups and steel tube;(3)The constraint effect of steel tube on concrete shows obvious spatial distribution characteristics;(4)the improved formulas can predict the eccentric load bearing capacity as a whole for.square steel tubular columns filled with highstrength steel angles or square steel tubular columns filled with stirrups or circle steel tubular columns filled with stirrups.