复式不锈钢管再生块体混凝土短柱轴压试验研究

Tests on composite-sectioned stainless CFST columns filled with demolished concrete lumps under axial compression

为了研究再生块体混凝土构件的受压性能,考虑不同取代率、不同新旧混凝土强度差以及不同钢管径厚比对再生块体混凝土构件受压力学性能的影响,进行了7个外方内圆复式钢管再生块体混凝土短柱和3个普通复式钢管混凝土短柱的试验研究。结果表明,在低强度的混凝土中添加高强度的再生混凝土块体,复式钢管再生块体混凝土短柱轴压承载力随取代率的增加呈上升趋势;添加与不添加再生混凝土试件破坏过程和破坏形态基本相似,鼓曲位置的混凝土局部压碎后,由于钢材的塑性变形能力较好,在方钢管环向约束下混凝土仍维持略微鼓曲,未散落破碎;内圆钢管明显环向鼓曲,新旧骨料结合较好,核心混凝土中未发现界面破坏的情况;试件具有良好的延性,加载结束时,试件尚能承担峰值荷载的60%以上,复式钢管再生块体混凝土短柱轴压承载力受径厚比和新混凝土抗压强度影响较大;采用直接叠加或考虑钢管对核心混凝土的约束作用但圆形截面予以折减的假定,计算所得承载力结果与试验结果吻合较好。

In order to study the compression performance of recycled concrete members, including the influence of different replacement rates, the strength difference between different concrete and steel pipe diameter-thickness ratios on the compression behavior of recycled concrete members, experimental study on 7 square stainless steel tubes filled with recycled demolished concrete lump mixture and reinforced by circular steel tube stub columns and 3 normal steel tube reinforced CFST(SR-CFST) stub columns. The results show that: when the high-strength recycled concrete block is added to the low-strength concrete, the axial bearing capacity of the SR-CFST stub columns filled with recycled concrete can be increased with the increasing replacement rate;the failure process and failure modes of the specimens with or without recycled concrete are quite similar, after the local crushing of the concrete at the local buckling position, the overall shape can be maintained rather than scattered and broken due to the good plastic deformation ability of steel,;the inner circular steel pipe is obviously hoop-shaped, the old and new concrete are well combined, and no interface damage is found in the core concrete;the tested columns have good ductility and deformation performance, which can still undertake more than 60% of the peak load at the end of the test;the axial bearing capacity of SR-CFST stub column filled with recycled concrete is affected by the diameter-thickness ratio and the compressive strength of the new cast concrete;the simplified methods direct superposition method or considering restraining effect to concrete, but the axial bearing capacity of circular CFST section should be reduced, the assumed calculation results are in good agreement with the experimental results.