Probabilistic model for steel–concrete bond behavior in bridge columns affected by alkali silica reactions

Past research has shown that in concrete bridges, cements with high alkali content combined with reactive siliceous aggregates can result in alkali silica reaction (ASR) in the presence of sufficient moisture. There is a concern that ASR may form at the steel–concrete interface and weaken the bond behavior in RC columns. This could result in a reduction of the structural capacity of columns and overall bridge reliability. Therefore, to accurately assess the column and bridge reliability over the service life of the structure, it is important to account for the possible effects of ASR on the steel–concrete bond behavior in the lap-splice region. This paper develops a probabilistic model of the steel–concrete bond behavior that considers the effects of ASR. The proposed model is formulated starting from a currently available bond–slip model suggested by CEB-FIP. Unknown parameters in the bond–slip model and their statistics are assessed through a Bayesian approach using available data from the load testing of eight large-scale bridge column specimens constructed to study the effect of ASR on the bond behavior in the lap-splice region. The experimental data do not directly show the bond behavior, but are in terms of the force–displacement response of the full specimens. Therefore, to assess the parameters in the bond–slip model, a finite element model is constructed to obtain the force–displacement responses as a function of the parameters in the bond–slip model. The results show that the bond stiffness and strength tend to increase for the specimens exhibiting moderate ASR deterioration, but decrease as ASR deterioration reaches a certain level.