Towards Crack-Based Assessment of Dapped-End Connections

Reinforced concrete dapped-end connections, which commonly feature in existing precast structures of bridges and other infrastructure, are known to present serious safety and durability concerns. These arise in part due to the formation of an inclined crack at the re-entrant corner of the connection, typically under service load conditions. The corner crack exacerbates corrosion issues and increases the stresses in the dapped-end reinforcement, which in the event of further deterioration and increased loading may lead to yielding and failure of the connection. This paper provides a description of a kinematics-based model that predicts the opening of the corner crack based on first principles: compatibility, equilibrium, and constitutive relationships. Model predictions are validated by comparing with measured crack width data from eight large-scale dapped-end connections featuring an orthogonal reinforcement layout. It is shown that, for all eight specimens the model predicts well the strength of the connection, as well as the crack widths at the re-entrant corner. The paper further discusses a method of translating on-site crack width measurements into useful knowledge about the residual capacity of dapped-end connections.