薄壁方钢管再生混合柱抗震性能试验研究

通过15根薄壁方钢管再生混合柱在定常轴力和水平往复荷载作用下的拟静力试验，研究了废弃混凝土取代率、钢管壁厚、轴压比等参数对试件抗震性能的影响。基于新、旧混凝土的组合强度，根据国内外钢管混凝土结构的设计标准以及基于ABAQUS的纤维梁单元模型，对试件的水平承载力进行了计算分析。研究表明：废弃混凝土取代率在0~40%之间变化对试件的初始抗侧刚度、钢管局部屈曲、破坏位移、负刚度段行为、等效黏滞阻尼系数、滞回曲线形状影响有限，但再生混合柱的水平承载力总体上比全现浇柱有所降低；当钢管壁厚在1.78~5.50mm之间变化时，随钢管壁厚增加试件并未表现出更好的变形能力；在钢管壁厚仅1.78 mm（宽厚比168.5）的情况下，轴压比0.4的再生混合柱的破坏位移角可达1/35，满足我国现行抗震规范的层间位移角限值要求；采用5部现行标准计算薄壁方钢管再生混合柱的水平承载力可获得与同条件全现浇柱相当的安全性；横截面积和用钢量相同时，薄壁方钢管再生混合柱的抗震性能优于钢筋混凝土柱。研究发现，薄壁方钢管再生混合柱应用于中、低轴压比（实际轴压比小于0.4）的情况是可行的。

Tests on seismic behavior of square thin-walled steel tubular columns filled with demolished concrete blocks

Tests of fifteen square thin-walled steel tubular columns filled with demolished concrete blocks (DCBs) under constant axial load and cyclic lateral load were conducted, and influences of some parameters (i.e., replacement ratio of demolished concrete, thickness of steel tube, and axial load ratio) on the seismic behavior of the specimens were investigated. Based on the concept of combined strength of the new and old concrete, and using the domestic and foreign design codes for concrete filled steel tubular structures and the fiber beam element model based on ABAQUS, the lateral load bearing capacities of the specimens were calculated and compared with the test results. It can be seen that the influences of replacement ratio of demolished concrete within a range of 0~40% on the specimens’ initial lateral stiffness, local buckling of steel tube, destructive deformation, behavior at negative stiffness stage, equivalent viscous damping coefficient, and shape of hysteretic curve are limited. But the lateral load bearing capacity of a specimen filled with DCBs is less than that without DCBs on the whole. With an increasing of the thickness of steel tube within a range of 1.78 mm~5.50 mm, larger deformation capacity is not observed for the specimens. In the case that the thickness of steel tube is only 1.78 mm (i.e., width-to-thickness ratio 168.5), the destructive deformation ratio of a specimen filled with DCBs with an axial load ratio of 0.4 reaches 1/35, meeting the requirement of interstory drift ratio specified in current seismic design code. Using 5 current design codes, the safety margin of the calculated lateral load bearing capacities for square thin walled steel tubular columns filled with DCBs is similar to that without DCBs. In the case that the sectional area and the steel ratio are unchanged, seismic properties of square thin-walled steel tubular columns filled with DCBs are better than those of reinforced concrete columns. It is applicable to use square thin-walled steel tubular columns filled with DCBs in low-and medium-axial load ratio conditions.