Seismic performance and damage evaluation of spiral ribbed thin-walled concrete filled and encased steel tube composite columns

As a new type of composite components, thin-walled concrete-filled steel tubes (CFSTs) have some advantages in terms of economy and processing. After the steel tube wall thins, the local buckling performance decreases and the stiffness decreases, which is not conducive to the structural safety. In this paper, combining the advantages of traditional spiral hoops and a stiffener, a new constraint in the form of a screw stiffener was proposed. On this basis, the composite member of thin-walled CFSTs with spiral ribs was put forward. The horizontal hysteretic test was carried out for the new composite column, and the failure mode, hysteretic characteristics, ductility, and energy dissipation capacity were obtained. The results showed that, compared with the traditional form, the seismic bearing capacity of the new composite column was increased by 11% and the ductility was increased by 45%. The deformation capacity was significantly improved. Based on experimental research, the seismic bearing capacity calculation and seismic damage assessment of the composite column were studied, and the practical calculation and the two-parameter damage assessment method considering the interaction between deformation and energy were proposed, which were in good agreement with the test results. This study can provide a technical basis for its engineering application. The composite column has good seismic performance, durability, and fire resistance, and thus has potential for application in practice.