Abstract:

This study experimentally investigated the effect of end restraint conditions on the axial compressive performance of concrete⁃filled glass fiber⁃reinforced polymer （GFRP） tube long columns. Monotonic axial compression tests were conducted on specimens under three distinct boundary conditions： both ends fixed， one end fixed and one end hinged， and both ends hinged. The failure modes， load⁃strain responses， ultimate bearing capacity， and lateral displacement were systematically analyzed. The results indicated that there was a transition in failure mode from a brittle end failure in fixed⁃fixed columns to global bending instability in columns with hinged ends. The fixed⁃fixed configuration demonstrated the highest ultimate bearing capacity and ductility. In contrast， the ultimate bearing capacity for the one⁃end⁃hinged and both⁃ends⁃hinged configurations decreased by 23.9 % and 25.5 %， respectively， while their ultimate axial strains were reduced by 53.4 % and 65.8 %. The lateral displacement was most pronounced in the both⁃ends⁃hinged configuration， with its peak value at ultimate load being 41.4 % and 35.8 % higher than that of the fixed⁃fixed and fixed⁃hinged configurations， respectively. The experimental data correlated well with an ideal buckling curve model. Furthermore， predictions from an existing stability factor model for ultimate bearing capacity showed good agreement with the test results. These findings underscore the critical importance of end restraint conditions in the design and stability analysis of concrete⁃filled GFRP long columns.

Key words: concrete?filled glass fiber reinforced polymer tube long columns, end restraints, axial compressive performance, ultimate bearing capacity model, lateral displacement