Experimental Study on Mechanical Properties of a GFRP-Confined Bamboo-Reinforced Concrete Composite Rod

A glass fiber-reinforced polymer (GFRP)-confined bamboo-reinforced fine aggregate concrete composite rod (GBCR) is proposed as a sustainable alternative to thin-walled steel tubes for compression and bending applications. Although FRP-confined concrete and FRP–bamboo composite members have been widely investigated, the mechanical behavior of slender members integrating a GFRP tube, large-section bamboo strips, and fine aggregate concrete under both axial compression and bending remains insufficiently understood. To address this gap, this study develops and experimentally evaluates the GBCR system using twelve short axial compression (SGC) specimens, seven slender axial compression (LGC) specimens, and ten long-span bending (LGB) specimens. The specific novelty of this work lies in the integrated assessment of short member compression, slender member stability, and bending behavior performed while considering bamboo type, bamboo content, relative filling compactness condition, bamboo strip orientation, and BPS splicing. The SGC specimens failed via axial crushing with GFRP expansion cracking and concrete fragmentation, while LGC specimens exhibited instability failure. Bending-resistant LGB specimens demonstrated brittle fracture behavior. The load-bearing capacity of the GBCR was significantly influenced by material composition, bamboo fiber content (optimal at ~20%), concrete density, bamboo orientation, and reinforcement integrity. Notably, the GBCR with 20% bamboo content achieved comparable or superior compressive strength to hollow steel tubes. Furthermore, LGC specimens exhibited excellent elastic recovery. Based on experimental observations, an empirical formula was developed to predict the ultimate axial compressive capacity. This study validates the GBCR’s potential as a cost-effective and eco-friendly solution for load-bearing components that leverages locally sourced bamboo resources.