中文摘要：

对9根外套钢管自密实混凝土加固钢筋混凝土中长圆柱和未加固钢筋混凝土中长圆柱进行轴心受压试验研究，研究长径比、钢管壁厚和后浇自密实混凝土强度对复合加固中长圆柱受力性能的影响。研究结果表明：未加固中长圆柱破坏形态属于局部强度破坏而复合加固中长圆柱的破坏属于弹塑性失稳破坏。长径比越小，复合加固柱承载力提高越大；随着后浇自密实混凝土强度的提高，复合加固柱极限承载力略有提高，但延性逐渐降低；钢管壁厚的增加能够显著提高复合加固柱的极限承载力和延性。在试验研究的基础上，提出外套钢管自密实混凝土加固钢筋混凝土中长圆柱的承载力简化计算公式，计算结果与试验结果吻合较好。

英文摘要：

A total of 9 RC column without strengthening and middle long RC columns strengthen by self-compacting concrete and steel tube were tested under the axial compression loads. The influences of length to diameter ratio, steel tube thickness and self-compacting concrete strength were studied. The results show that the specimens without strengthening appear as strength failure modes, while the reinforced specimens appear as elasticoplasticity failure modes. With the decrease of length to diameter ratio, the load bearing-capacity of the reinforced specimens increase. With the strength of the self-compacting concrete increasing, the load bearing capacity of the reinforced specimens increase a litter, while the ductility decrease to some extent. With the steel tube thickness increasing, the load bearing capacity and the ductility of the reinforced specimens increase obviously. On the basis of the experiments, a simple formula is proposed to calculate the load bearing capacity of the specimens. The calculation results agree well with the experimental ones, which proves the effectiveness of the proposed formula.