压-扭作用下中空夹层钢管混凝土的破坏机理分析

Analysis of the Failure Mechanism of Concrete Filled Double Skin Steel Tube Under Compression-Torsion

为了分析中空夹层钢管混凝土在压-扭复合受力下的破坏机理,对24根中空夹层钢管混凝土进行了压-扭静力试验,分析了受力全过程中中截面应变的开展规律及轴力对扭转刚度的影响,并通过扭转变形各阶段中截面横向应变与剪应变的开展,分析了轴力对外钢管约束效应的影响。结果表明:轴压比较大时,扭矩-转角(T-θ)曲线在弹性范围内出现明显的拐点,轴力提高了初始抗扭刚度;圆中空夹层钢管混凝土中截面不同位置处的扭矩-应变(T-ε)曲线重合度较高,相较于方形截面,其对内部结构的约束更均匀;扭矩加载初期,方形截面外钢管角部与中部的环向应变及剪应变相近,加载后期,中部的剪应变大于角部,角部的环向应变大于中部,表明角部出现应力集中,对内部结构的约束效应更明显,同时受力全过程中角部的相互作用力均大于中部。

In order to analyze the failure mechanism of the concrete filled double skin steel tube(CFDST)under compression and torsion,the compression-torsion static test was carried out on 24 pieces of concrete filled double skin steel tubes.The strain development of the middle section during the whole process and the effect of the axial force on the torsional stiffness were analyzed.Through the development of hoop strain and shear strain of middle section in each stage of torsional deformation,the influence of axial force on restraint effect of the outer steel tube was analyzed.The results show that when the axial compression ratio is relatively large,the T-θcurve has an obvious inflection point in the elastic stage,and the axial force increases the initial torsional stiffness.The circular CFDST has a higher degree of coincidence of the T-εcurves at different positions of the middle section,and compared with the square outer tube,it has a more uniform restraint effect on the internal structure.At the beginning of torque loading,the hoop strain and shear strain at the corner of the outer steel tube with square cross-section are similar to the middle.At the later stage of torque loading,the shear strain in the middle is greater than that in the corner,but the hoop strain in the corner is greater than that in the middle,which shows that there is stress concentration in the corner,and the restraint effect on the internal structure is obvious.At the same time,the interaction force of the corner is greater than that of the middle during the whole process.