A simplified tri-linear model for monolithic exterior shear keys failing in sliding shear

This paper proposes a simplified tri-linear model for the lateral force-displacement relationship of monolithic exterior shear keys in reinforced concrete bridges, failing in sliding shear. To allow for implementation compatibility with a widely used simplified model for shear keys failing in diagonal tension (DT), this model is presented in a tri-linear formulation that builds on past experimental data and expressions for the capacity of shear keys. Capacity points are adapted from previously published work on sliding shear (SS) and sliding friction (SF) failing shear keys, and displacement points are devised around available experimental data and numerical studies. These consider the effective stiffness of concrete members, dowel action in vertical steel reinforcement, and empirical observations from monolithic shear key tests. Model parameters are probabilistically characterized in a Bayesian parameter estimation framework, to incorporate experimental data. The calibrated expressions are then validated by comparing sampled predictions to experimental observations, and finally a single distribution for model parameters is suggested. The goal of this model is to provide a simplified formulation to be implemented alongside DT failure in time-history response simulations of structure-level finite element models of bridges, thus covering both major failure mechanisms in monolithic reinforced concrete shear keys.