Bond-slip model for coarse sand coated interface between FRP and concrete from optimization technique

Innovative FRP–concrete composite bridge deck systems fabricated by casting concrete above FRP panel have been proposed and have already been implemented actually. In such deck systems, the FRP panel plays the role of formwork during the curing of concrete and behaves as a structural member combined with concrete during service life. Coarse sand coating is usually applied to secure composite behavior of the two materials instead of epoxy bonding, which is extensively used for retrofit purpose of deteriorated structures. This study focuses on investigating the bond behavior of coarse sand coating experimentally and analytically. Pure shear tests on coarse sand coated and epoxy coated joints are performed from which results are used to extract the bond-slip model. A method to obtain the bond-slip model from pure shear test is proposed, in which analytic solution of bond-slip model based on fracture mechanics is introduced and physical programming technique is used for formulation. Genetic algorithm is adopted for the optimization. Application of the proposed method produces local bond-slip model for coarse sand coating. Finally, in order to verify the proposed method and local bond-slip model, 4-point bending test of beam specimens with coarse sand coated FRP plate is performed and the result is compared to finite element analysis including the proposed local bond-slip model.