Behavior of concrete columns confined by carbon composite tubes

The carbon composite tube can play an important role in replacing or complementing longitudinal and transverse reinforcing steels by providing ductility and strength for conventional columns. In this study, both experimental and analytical investigations of axial behavior of large-scale circular and square concrete columns confined by carbon composite tubes are presented. The specimens are filament-wound carbon composite with 90° + 90°, 90° ± 60°, 90° ± 45°, and 90° ± 30° winding angles with respect to a longitudinal axis of a tube. The instrumented large-scale concrete-filled composite tubes are subjected to monotonic axial loads exerted by a 10 000 kN universal testing machine (UTM). The influence of transverse dilation, winding angle, thickness of a tube, as well as shape of the column section on stress–strain relationships of the confined columns is identified and discussed. Proposed equations to predict both strength and ductility of confined columns by carbon composite tubes demonstrate good correlation with test data obtained from large-scale specimens.Key words: carbon composites, glass fibers, strength, filament winding.