Local FRP Cracking and Global Structural Behavior of Stub Concrete-Filled FRP Tubes under Concentric and Eccentric Compression

This paper examines experimental data from 22 large-scale concrete-filled FRP tubes (CFFTs), each 900 mm in length and 300 mm in diameter, subjected to either concentric or eccentric compression. The study encompasses CFFTs composed of normal-strength concrete (NSC) and high-strength concrete (HSC), employing glass fiber-reinforced polymer (GFRP) tubes with fiber angles of 60 degrees and 80 degrees. A primary focus of this study is investigating the cracking behavior of GFRP tubes in CFFTs during loading, a durability/serviceability-related issue that has received limited attention in existing literature. Based on the test data, the study identifies two distinct types of cracking: tension-induced cracking under eccentric compression and hoop crushing under either concentric or eccentric compression. The paper delves into the underlying mechanisms behind these cracking phenomena and thoroughly explores the influence of variables such as fiber-reinforced polymer (FRP) tube thickness, fiber angle, and the type of concrete core on the observed cracking behavior. Meanwhile, the paper provides an in-depth analysis of the structural behavior of CFFTs, with a focus on aspects such as GFRP tube thickness, fiber angle, and the differences between NSC and HSC cores. These experimental results not only enhance the understanding of the behavior of large-scale CFFTs under concentric or eccentric compressions but also offer crucial insights into the differences in the compressive behavior of FRP-confined NSC columns and FRP-confined HSC columns. Additionally, the comparative analyses of local cracking behavior with the global behavior of CFFTs contribute vital information toward the development of a design method of CFFT columns in practice, with different considerations of the issues in the ultimate limit state and serviceability limit state (e.g., the corrosion protection capabilities of the GFRP tube in CFFTs).