Experimental investigation of a simple shear connection to concrete-filled FRP tube (CFFT) columns

Abstract

The concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) system has been widely studied as a robust alternative to conventional reinforced concrete (RC) for column construction. Despite the superior structural performance of this column system in terms of durability, strength and ductility, its application in building construction is limited due to a lack of viable designs for beams-to-column connections. To address this gap, this study proposes a simple connection for a circular CFFT column and a steel I-shape beam. The connection consists of a curved end plate with a shear tab that is attached to the finished CFFT using commercially available concrete anchors. In this study, three connection assemblies with adhesive and expansion anchors were tested under half-cyclic loading. The connection assemblies varied based on the type of the anchors and installation torque. The performance was evaluated in terms of ease of construction, shear capacity, moment-rotation relationship, and observable damage. The FRP shell eliminated concrete breakout failure and the anchors exceeded the theoretical pullout capacity noted by the manufacturer. A methodology for estimating the proof load of the proposed connection detail is presented. The proposed connection provides a viable option for simple connection of steel beams to circular CFFT columns. The findings may inform future research on beam-column connections for CFFTs and lead to an increased use of CFFT systems in building construction.