Performance of Circular Concrete-Filled FRP-Grooved Steel Composite Tube Columns under Axial Compression

A new structure termed concrete-filled FRP-grooved steel composite tube (CFGCT) column is proposed, which is composed of a stress-released steel tube (i.e., grooved steel tube), fiber-reinforced polymer (FRP) and concrete. Axial load tests were carried out on twenty-four specimens to investigate the constraint effect of this structure. Three main experimental variables were considered: the steel tube thickness, the FRP type, and the FRP layer. The failure modes, stress-strain relationships and the effect of the main experimental variables were discussed. The stress-strain curves of this new structure are composed of an initial linear part, a nonlinear transition part, a strengthening part and a residual part. The test results demonstrate that the bearing capacity of the structure was improved, and that the mechanical mechanism of the structure was simplified due to the stress-released grooves. Based on the test results and previous studies, formulas for calculating the ultimate stress (f(cu)), ultimate strain (epsilon(cu)), peak stress (f(cc)) and peak strain (epsilon(cc)) were proposed. In addition, models for predicting the stress-strain curves of CFGCT columns were put forward, and the models could precisely simulate the stress-strain curve of this new composite structure. Hence, this study indicates that a structure composed of FRP and stress-released steel tube can effectively constrain concrete.

Automated summary

The new CFGCT column structure composed of stress-released steel tube, FRP, and concrete showed improved bearing capacity and simplified mechanical mechanism. Formulas for calculating ultimate stress, ultimate strain, peak stress, and peak strain were proposed based on test results, and models for predicting stress-strain curves of CFGCT columns accurately simulated the behavior of this new composite structure.