Mechanical behavior of GFRP-bamboo composite shear connections

Sustainable development has become an important and urgent topic for civil engineering. More and more green and renewable materials, like engineered bamboo, have been designed to work with other traditional building materials to utilize the ecological benefit and mechanical advantages. Nonetheless, few researches investigated the mechanical performance of the composite structure made of fiber-reinforced polymer and engineered bamboo. A new composite connection made of pultruded H-section glass fiber-reinforced polymer (GFRP) profile and engineered bamboo was proposed and studied by push-out tests to assess the shear performance. A total of 46 specimens with bolted, glue or hybrid connectors were tested to investigate the influence of the connection type, bolt diameter and spacing, as well as the bamboo thickness, on the strength and stiffness of GFRP-bamboo connections. The load-carrying capacity and shear stiffness were analyzed, and three types of failure modes were identified. When the bamboo thickness was 17 mm and 20 mm, a single plastic hinge was formed in the shear connectors, and the bamboo panels performed splitting and edge crushing failures. When the bamboo thickness was 34 mm and 40 mm, two plastic hinges formed in the connectors with embedment failure in the bamboo panels. Nonetheless, when using glue connection, brittle and undesirable failure occurred. When increasing the bamboo thickness from 17 mm to 34 mm, the average peak load increased from 67.52 kN to 100.64 kN, and the yield and ultimate loads both increased by about 49%. In addition, the results showed that hybrid connections were more effective than bolted and glue connections. The average peak load of hybrid connections increased by 42.72% and 13.16% compared to that connected with glue and bolts, respectively. The experimental results were compared with those calculated according to Eurocode 5-1995 and GB/T50005-2017, and it could be concluded that the formulas of the codes were not suitable for such shear connections due to the conservative design. To predict the nonlinear behavior of the specimens, the theoretical model based on Foschi formula was built. The analytical predictions showed good agreement with the test results in case of bolted connections. In a word, the shear performance and theoretical model of the proposed composite shear connections make it possible to predict the bending strength and stiffness of GFRP-bamboo composite beams, but the sharp drop of load-carrying capacity induced by the failure of glue connection needs more consideration and research.