Experimental, Analytical and Numerical Study of RC Dapped Ends with Multi-Oriented Reinforcement

The load-carrying capacity of reinforced concrete (RC) dapped ends is often estimated using Strut-and-Tie (S&T) models, which remain the most effective tool for predicting the resistance of D-regions. Nevertheless, the conventional S&T models, like the two truss models provided by EC2 for dapped ends, refer to reinforcement layouts with horizontal and vertical ties only, as well as to reinforcement layouts with diagonal ties only. Moreover, both models assume that ties are isolated or concentrated in a narrow band, so they require a modification to apply to cases where the steel bars are distributed. This paper investigates the structural response of eight full-scale RC dapped ends with identical geometry and size, but different reinforcement layouts. The first two layouts feature concentrated reinforcement: one with horizontal and vertical ties only, and the other with diagonal ties only. Two additional dapped ends are provided with distributed bars following the same layouts. The remaining four dapped ends are equipped with combinations of the previous layouts, using concentrated and/or distributed reinforcement. The ultimate loads of all specimens were predicted using a nonlinear finite element model and were subsequently assessed through bending tests. The ability of the S&T models to predict the experimental data was also verified. The experimental tests, combined with nonlinear numerical modeling, produced valuable insights that may guide the future development of enhanced strut-and-tie models for both the design of new dapped ends and the assessment of existing ones.