带约束拉杆T形钢管混凝土短柱偏压试验研究

Experimental study of T-shaped CFT stub columns with binding bars subjected to eccentric load

进行了16根带约束拉杆和11根不带约束拉杆T形钢管混凝土短柱试件的偏压试验研究,分析了不同荷载角、偏心率、约束拉杆间距下该类型柱的偏压性能。试验结果表明:约束拉杆的设置减小钢板的屈曲半波长、延迟钢管局部屈曲的发生、提高核心混凝土的约束作用,有助于提高该类型柱的承载力和延性;临近或达到极限荷载时近力侧拉杆及钢板对核心混凝土的约束作用明显,且约束作用从近力侧向远力侧减小;偏心受压下该类型柱的截面应变符合平截面假定。采用带约束拉杆T形钢管混凝土短柱的核心混凝土等效单轴本构关系,利用纤维模型法程序对该类型柱进行参数研究。分析结果表明:钢材屈服强度、含钢率越大,N/Nu-M/Mu相关曲线向内收拢;混凝土强度和拉杆约束系数越大,N/Nu-M/Mu相关曲线向外凸出。

A total of 16 T-shaped concrete-filled steel tubular（T-CFT） stub columns with binding bars and 11 specimens without binding bars were tested under eccentric compression.The influences of the loading angle,load eccentricity ratio and spacing of binding bars on the eccentric load behavior of this kind of columns were investigated.Test results indicate that setting binding bars result in the decrease of the half buckling wave length of the steel tubes,the delay of local buckling of the steel tubes,the improvement of the confinement effects on the core concrete,and the increase of load carrying capacity and ductility of the specimens.Steel plates and binding bars near the maximum compressive side exhibit obvious confinement effects on the core concrete when approaching or reaching the maximum load.The confinement effects decrease from the maximum compressive side to the minimum compressive or the maximum tensile side.The strain distribution on the column section under eccentric compression conforms to the assumption that plane section remains plane.Based on the equivalent uniaxial stress-strain relationship for the encased concrete in the T-shaped stub steel tube with binding bars,the fiber element analysis result was verified by the experiments and adopted to carry out the parametric studies to further study the fundamental behavior of eccentrically loaded T-shaped CFT stub columns.The analysis results indicate that the N/Nu-M/Mu curves will shrink inward along with the increased steel yield strength or sectional steel ratio,while will expand outward along with the increased concrete compressive strength or confinement coefficient of binding bars.