Axial behavior of square reinforced concrete columns strengthened with lightweight concrete elements and unbonded GFRP wrapping

This paper presents a new, efficient, and economic confinement technique for square reinforced concrete (RC) columns with unbonded glass fiber-reinforced polymer (GFRP) wrapping and lightweight concrete elements at the side faces. Three confined columns with different reinforcement ratios were tested under concentric axial force. The force-deformation responses show a distinctly increased load-carrying capacity at plastic deformations up to 4% average axial strain. This confinement technique is a considerable improvement for square columns with a large side-to-corner radius. Only a slight change in column geometry has to be accepted because of the use of unbonded lightweight concrete panels.