Flexural behavior of hybrid FRP-concrete-steel double-skin tubular member T-joints subjected to in-plane bending
Guan Lin, Yuanze Guo, Xinchao Lin, Kostiantyn Protchenko, Junjie Zeng
Abstract
Hybrid FRP-concrete-steel double-skin tubular members (DSTMs) offer a promising solution for ocean engineering structures due to their superior mechanical properties and durability. While extensive research has been conducted on the axial and flexural behavior of DSTMs, the behavior of DSTM joints remains relatively unexplored. This study aims to address this gap by experimentally investigating the in-plane bending behavior of DSTM T-joints, focusing on the influence of key parameters including brace tube diameter, FRP thickness, and axial compression ratio in the chord. The experimental program included tests on four large-scale DSTM T-joint specimens and one hollow steel tubular (HST) joint specimen. The test results demonstrated that the DSTM T-joint specimens exhibited superior performance in terms of load-carrying capacity and ductility (the ductility indices of all the DSTM T-joint specimens were larger than 4.0). The thickness of the FRP tube/wrap and the diameter of the brace were identified as the two most crucial parameters affecting the performance of the joint specimens. Compared with the HST joint specimen, the presence of the annular concrete and FRP confinement in DSTM T-joint specimens significantly enhanced the joint performance (the enhancement percentages ranged from 196 % to 244 %). The axial load ratio of the chord had little influence on the lateral load-carrying capacity but had a negative effect on the ductility of the test DSTM T-joint specimens. This study provides valuable insights into DSTM T-joints and underscores the need for further research to enhance their practical implementation.