Push-out behavior of GFRP bolts shear connectors in FRP-concrete hybrid beam

Abstract

GFRP bolt has emerged as a promising shear connector in FRP-concrete hybrid beams due to flexible arrangement and ease of installation. Shear connectors are critical to maintaining the composite action and are key to the design of hybrid beams. 30 push-out tests were conducted to investigate failure mode, ultimate strength, and shear load-slip (P-S) relationship of GFRP bolts. Test parameters included bolt types, layout of bolts, longitudinal row spacing of bolts (Sl), bolt diameter (d), and bolt embedment depth (he). Results revealed that specimens with GFRP bolts exhibited bolt shank shear failure, pry-out failure of bolts, and splitting failure of concrete. In contrast, specimens with stainless-steel bolts suffered bearing failure of bolt holes in the FRP flange. Typical P-S curves of GFRP bolt specimens consisted of micro-slipping and significant-slipping phases, showing non-linear response, while P-S curves of stainless-steel bolts exhibited a linear response till failure. The effect of layout of bolts was found negligible if the longitudinal row spacing and horizontal spacing was not less than 6d and 4d, respectively. Specimens with a larger d and he demonstrated greater shear capacity. Based on the test results, prediction equations associated with failure modes were introduced to predict the capacity of GFRP bolt, which yielded results in accordance with experiments. Additionally, a refined description of P-S relationship was proposed by curving fitting, and the results correlated well with the experiments.