A typical fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular column (DSTC) consists of an FRP outer tube, a hollow steel inner tube and an annular concrete in-fill in between. The existing studies on DSTCs in the past decade have generally confirmed the good structural performance of such column form, while it is worth noting that the possible in-ward buckling of the steel tubes in DSTCs is still a problem to be addressed, especially when DSTCs are subjected to large axial deformation. Against this background, a variation form of DSTCs called R-DSTCs has been recently developed by the authors. An R-DSTC is a DSTC in which the steel inner tube is reinforced by vertical stiffeners on the outer surface and the FRP outer tube can be circular, square or rectangular. The present paper presents the first ever experimental study on the compressive behavior of circular R-DSTCs which is the most common form of DSTCs. For the circular R-DSTC specimens tested in the present study, the outer tubes are made of a type of large-rupture-strain FRP. The vertical stiffeners on the steel inner tube are expected to delay or restrain the inward buckling of the steel tube, and the large-rupture-strain FRP outer tube makes possible a relatively large axial deformation of the specimen. In total, two DSTC specimens, twelve R-DSTC specimens and three bare steel tubes with/without stiffeners were tested, with the studied parameters covering the quantity, the dimensions and the shape of the stiffeners and the thickness of the FRP outer tube. The test results showed that R-DSTC specimens had a much better performance than the corresponding DSTC specimens in terms of both axial loading capacity and ductility, due to the existence of vertical stiffeners on the steel inner tube of R-DSTCs. The effects of the vertical stiffener-related parameters on the compressive behavior of R-DSTC specimens were also carefully examined and discussed in details.

典型的纤维增强聚合物（FRP）-混凝土双皮管形柱（DSTC）由FRP外管，空心钢内管和介于两者之间的环形混凝土填充物组成。过去十年中对DSTC进行的现有研究总体上证实了这种立柱形式的良好结构性能，但值得注意的是，DSTC中钢管可能的向内弯曲仍然是一个有待解决的问题，尤其是当DSTC时承受较大的轴向变形。在这种背景下，作者最近开发了一种称为R-DSTC的DSTC变体形式。R-DSTC是一种DSTC，其中钢制内管由外表面上的垂直加强筋加强，而FRP外管可以是圆形，正方形或矩形。本文提出了关于圆形R-DSTC压缩行为的首次实验研究，R-DSTC是DSTC的最常见形式。对于在本研究中测试的圆形R-DSTC标本，外管由一种大断裂应变FRP制成。预期钢内管上的垂直加强筋会延迟或限制钢管的向内屈曲，而大断裂应变的FRP外管则可能使试样产生较大的轴向变形。总共测试了两个DSTC试样，十二个R-DSTC试样和三个带有/不带有加强筋的裸钢管，研究的参数涵盖了加强筋的数量，尺寸和形状以及FRP外管的厚度。测试结果表明，由于R-DSTC的钢内管上存在垂直加强筋，因此在轴向载荷能力和延展性方面，R-DSTC试样的性能均优于相应的DSTC试样。还仔细检查了垂直加劲肋相关参数对R-DSTC试样压缩行为的影响，并进行了详细讨论。