Development of probabilistic FRP-to-concrete bond strength models for externally-bonded reinforcement on grooves: Bayesian approach

Recent years have witnessed the superiorities of a grooving technique, i.e., the externally-bonded reinforcement on grooves (EBROG), over the traditional technique, i.e., externally-bonded reinforcement (EBR), in terms of strengthening reinforced-concrete members by fiber-reinforced polymer (FRP) composites. Similar to EBR, the prediction of interfacial bond strength is critical for the EBROG type of FRP-to-concrete joints. There have been a series of experiments conducted to study the bond strength of EBROG joints, however, the corresponding pre-diction models (especially those capable of uncertainty quantification) are rarely available. Therefore, this paper aims to develop probabilistic models able to both predict the bond strength of EBROG joints and quantify the associated uncertainties. Firstly, an experimental database containing 304 bond strength tests for EBROG joints with longitudinal grooves is collected. Secondly, two widely-accepted deterministic bond strength models are selected as candidates to be calibrated by including a model correction factor. Thirdly, the factor is expressed by power and exponential functions of the influencing variables, meanwhile the deterministic model parameters are replaced with probabilistic ones. Finally, the probabilistic models are determined by means of Bayesian inference and Markov chain Monte Carlo. Moreover, an approximate analytical expressions are derived to achieve the probabilistic bond strength prediction. The experimental database is used to investigate the model performances, and the results show that: 1) the developed models can predict the FRP-to-concrete bond strength of EBROG joints with sufficient predictive accuracies and reasonable uncertainty quantifications; 2) the groove geometry has significant influence on the model correction factor; and 3) the developed probabilistic models is only applicable to EBROG joints with longitudinal grooves, but not to ones with transverse/diagonal grooves.