08.57: The friction investigation of CFRP confined CFST specimens with modified concrete

Abstract

Nowadays, concrete filled steel tube (CFST) composite members have in wide range application areas such as transverse beams, piers, slender columns, stub columns, wind turbines etc. around the world. The frictional behavior between concrete and steel tube has a vital role in selection of required size and materials during the laboratory experiments, in-situ applications and modelling studies. In this study, 16 CFST members were subjected to push out tests within the aim of determination the effect of carbon fibres reinforced polymer (CFRP) confinement and modified concrete at the same time. Modified concrete indicates some mechanical additives are inside the concrete for instance steel fibres, polypropylene fibres and crumb rubber. Furthermore, external CFRP confinement was applied with three different arrangements on the outside circumference of the steel tube. Frictional stress created on the lateral interaction surface ranges between 0.18 MPa and 0.63 MPa due to maximum striping force. Maximum frictional strength was observed on the unconfined reference concrete. Although CFRP application seriously increased the axial strength of composite sections, this process decreases the frictional strength between concrete and steel tube, unexpectedly. Therefore, considering different frictional coefficient emerges as a foregone conclusion during the design procedure of CFRP confined CFST sections.