On the Verification of Discontinuity Regions in Existing RC Structural Elements Using Strut and Tie Models

Reinforced concrete (RC) discontinuity regions (D-regions), such as dapped ends and corbels, can represent highly vulnerable zones in existing RC structures, since they are characterized by brittle failure mechanisms. In common design practice, the ultimate strength of D-regions is assessed through Strut and Tie models (STM). The present work shows that, if on the one hand, the resistant lattice trusses suggested by construction standards like Eurocode 2 are on the safe side in the design phase, on the other hand, they can provide non-conservative results in the assessment of the ultimate strength of existing D-regions, as they cannot be appropriate to reproduce the actual distribution of steel reinforcement. Within this work, some indications are provided to identify the resistant mechanisms of D-regions in existing RC members together with some preliminary indications how to increase their ultimate strength and ductility.