Experimental Study And Calculation Method Of Concrete-filled Square Steel Tubular Column With Spiral Stirrups

Square steel tube can not effectively restrict the core concrete in square concretefilled steel tubular column, which can not effectively improve the compressivestrength of the core concrete in square concrete filled steel tubular column. In order tofully improve the core concrete compressive strength and the capacity plasticdeformation of the steel square tubular column, the spiral stirrups is configured toeffectively restrict the deformation of the core concrete of the concrete filled steeltubular column. The spiral stirrups can improve the bearing capacity and plasticdeformation of the concrete filled steel tubular column. The mechanical propertiesand failure modes of the square concrete filled steel tubular column and the squareconcrete filled steel tubular column with spiral stirrups is studied through experiments,and study calculation method of bearing capacity of the square concrete filled steeltubular column and the square concrete filled steel tubular column with spiral stirrups.The experimental results show that the bearing capability of concrete filled squaresteel tubular with spiral stirrups column is41％higher than that of concrete filledsteel tubular column. Because of the constraint of spiral stirrups on core concrete,transverse strain of the concrete filled square steel tubular column with stirrups is lessthan of the square concrete filled steel tubular column. Transverse strain of theconcrete filled square steel tubular column with spiral stirrups changes is moreuniform from the top to the bottom. Relative to the increase of the diameter of thespiral stirrups, reduce of the spiral stirrup space can be more effective to increase theultimate bearing capacity and ductility for the concrete filled square steel tubularcolumn with spiral stirrups.Superimposed theoretical formula is simple, and easy to be used in practicalengineering. The bearing capacity of the principle of superposition can not reflect theeffect which square steel confine core concrete. The core concrete of the concretefilled square steel tubular is divided into the effective confinement region andnon-effective confinement region. On the base of superimposed theory, the bearingcapacity of the concrete filled square steel tubular columns superimposed the bearingcapacity of the three parts, which include in the effective confinement region andnon-effective confinement region and square steel tube. In final, the formula ofbearing capacity of the concrete filled square steel tubular column is derived. The core concrete of the concrete filled square steel tubular with spiral stirrups isdivided into effective confinement region of the square steel tubes and spirals stirrups,effective confinement region of spirals stirrups, and non-effective confinement region.On the base of superimposed theory, the bearing capacity of the concrete filled squaresteel tubular columns superimposed the bearing capacity of the four parts, whichinclude in t effective confinement region of the square steel tubes and spirals stirrups,effective confinement region of spirals stirrups, and non-effective confinement region.and square steel tube. In final, the formula of bearing capacity of the concrete filledsquare steel tubular with spiral stirrups column is derived.The square concrete filled steel tubular column is equivalent to a circular thesquare concrete filled steel tubular column, and limit equilibrium theory is used in thecalculation of the bearing capacity of t the square concrete filled steel tubular columnat the first. In final, the formula of bearing capacity of the concrete filled square steeltubular column is derived.