薄壁方钢管再生混合短柱轴压性能试验研究

通过16个薄壁方钢管再生混合短柱的轴压试验，研究废弃混凝土取代率、新旧混凝土强度差、钢管壁厚等因素对试件轴压性能的影响；基于新、旧混凝土的组合强度，对比分析国内外相关公式预测试件轴压承载力的有效性。研究结果表明：与全现浇薄壁方钢管混凝土短柱相比，薄壁方钢管再生混合短柱的钢管屈服较早，废弃混凝土取代率越大钢管屈服越早；薄壁方钢管再生混合短柱的轴压承载力总体呈现出随废弃混凝土取代率增加逐渐降低的趋势，降低幅度大于薄壁圆钢管再生混合短柱；当新、旧混凝土抗压强度相近时，取代率在20%~33%范围内变化对薄壁方钢管再生混合短柱的轴压承载力影响有限；为使再生混合短柱具有与全现浇短柱相近的安全性，建议对根据现行设计标准计算得到的薄壁方钢管再生混合短柱的轴压承载力乘以调整系数0.9。

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

Sixteen stub square thin-walled steel tubular columns filled with demolished concrete blocks (DCBs) were tested under axial loadings. Influences of some parameters (such as replacement ratio of DCBs, strength difference between fresh concrete (FC) and DCBs, and thickness of steel tube) on the axial compressive properties of the specimens were investigated. Based on the combined strength of the FC and DCBs, the axial compressive bearing capacity of the specimens was calculated, according to the current formulas for stub concrete filled square steel tubular columns, and compared with the measured results. Tests and calculation results show that the steel tube of a column filled with DCBs yields earlier than that of a column only filled with FC. The larger the replacement ratio of DCBs is, the earlier the steel tube yields. With an increasing of the replacement ratio of DCBs, the axial compressive bearing capacity of the specimens filled with DCBs decreases gradually on the whole. In the case that the strength difference between the FC and DCBs is limited, the influence of the replacement ratio within a range of 20%~33% on the axial compressive bearing capacity of the specimens filled with DCBs is limited. To achieve a similar safety margin for both the specimens with and without DCBs, the axial compressive bearing capacity of the specimens with DCBs can be determined according to the current design codes and considering a reduction factor of 0.9.