Experimental study and performance evaluation of compression members in space structures strengthened with assembled outer sleeves

The buckling of compression members in space structures leads to the local collapse or even progressive collapse of structures. This paper proposed an assembled outer sleeve to reinforce the compression member of space structures by restraining its buckling. The assembled outer sleeve was composed of two identical semicircular anchor plates using high-strength bolts. The compression member to be strengthened does not need to be reformed directly. The mechanical properties of a compression member strengthened by an assembled outer sleeve were studied through axial compression tests involving eight specimens. The ultimate bearing capacity of a compression member strengthened by an assembled outer sleeve increased by more than 68.6%. When the wall thickness of the assembled outer sleeve was larger and the length of the unrestrained segment for the compression member was shorter, the ultimate bearing capacity of the specimens was higher. The installation direction of the assembled outer sleeve had no noticeable effect on the mechanical properties of the specimen. Furthermore, failure modes of the compression member strengthened by the assembled outer sleeve were proposed. The failure modes included the global buckling of the specimen, local buckling of the unrestrained segment for the compression member, and the coupled buckling (including global buckling and local buckling). When the wall thickness of the assembled outer sleeve was thin, global buckling was more likely to occur. Moreover, when the unrestrained segment for the compression member was long, local buckling was more likely to occur. Compared with the unreinforced compression member, the ductility coefficient of the compression member strengthened by the assembled outer sleeve enhanced by more than 49.7%. Compression members strengthened with assembled outer sleeves have an excellent post-yield axial deformation capability.