大径宽比钢管混凝土叠合柱轴压试验

Experiment on Axial Compression of Concrete Filled Steel Tube Composite Columns with Large Diameter Width Ratio

为研究大径宽比钢管混凝土叠合柱的轴压性能,设计制作了外径在400~600 mm范围内、含钢管率在3.70%~6.75%范围内的6根大径宽比钢管混凝土叠合短柱试件,并对其进行轴压试验。使用亚克力棒测量了钢管内部混凝土的应变,给出了不同柱径试件各部位的典型应变增长曲线。结合试验结果,引入考虑试件尺寸效应的混凝土材料强度折减系数,提出了适应大径宽比钢管混凝土叠合柱的极限承载力计算公式。结果表明:大径宽比叠合柱达到峰值荷载后承载力下降缓慢,具有较好的延性;含钢管率的提升直接增强叠合柱的承载力,含钢管率为6.08%的试件比含钢管率为3.70%的试件承载力高27.3%;不同尺寸试件的破坏特点存在差异,一般表现为尺寸越大,破坏越显脆性,但不同尺寸试件的各部位典型应变增长模式基本一致;叠合柱外部钢筋混凝土在加载中后期对承载力贡献较小。

In order to study the axial compression performance of concrete filled steel tube composite columns(CFSTCC)with larger aspect ratio,the axial compression test on six CFSTCCs with large diameter width ratio was completed.The diameter of the composite column was in the range of 400-600 mm and the steel pipe ratio of the composite column was in the range of 3.70%-6.75%.The strain of concrete inside the steel tube was measured with some acrylic rods,and the curves of typical strain growth in different parts of specimens with different diameters were given.Combined with the test results and size effects,the material strength reduction factor of concrete was introduced into the in composite columns,and the calculation formula of the ultimate bearing capacity for the CFSTCC with large diameter width ratio was proposed.The results show that the bearing capacity of CFSTCC with large diameter width ratio decreases slowly after reaching the peak load and has good ductility.The increasing of steel tube ratio directly enhances the bearing capacity of CFSTCC,and the bearing capacity of the specimen with 6.08%steel tube ratio is 27.3%higher than that of the specimen with 3.70%steel tube ratio.The specimens with different sizes have their own failure characteristics.Generally,the larger the size is,the more brittle the failure is,but the typical strain growth patterns of different size specimens are basically the same.The contribution of reinforced concrete outside the composite column to the bearing capacity is relatively small in the middle and later period of loading.