Study on The Structural Behavior of Precast Concrete Dapped-End Beams with Different Reinforcement Detail

Abstract

The experimental program & The analysis using three-dimensional nonlinear finite element modeling for dapped ends beams presented in this thesis. The experimental program consisted of testing dapped end beam specimens to examine the behavior of eight reinforcement schemes for the dapped ends. Several conclusions were presented based on the results of the experimental program. Recommendations for future studies are also given in this chapter.

7.2 Conclusion Based on the specimens' structural behavior during the test and an evaluation of the test data, this experimental program's following conclusions are drawn. 1. A similar crack pattern in all specimens was detected. Cracks started with diagonal re-entrant crack, followed by nib inclined crack and diagonal tension crack (developed in the beam's full-depth). 2. The re-entrant corner is the weakest portion of the beam, where stress concentration develops. 3. The First crack propagation started in all specimens between 11.7% to 18.4% from the total ultimate load. 4. According to the (PCI 7th Edition), the dapped-end reinforcement designed is conservative since the ultimate experimental load was overestimated that of the PCI equation by about (38.3%). Failure loads were observed much higher than the design loads. 5. The dapped ends with flexure reinforcement inclined and anchored by the welded plate from the top (S-4R), the failure load has increased by 53.1% higher than Control Specimen with PCI reinforcement scheme (S-2R).

6. The dapped ends with the flexure reinforcement placed inclined with practical anchorage and proper anchorage(S-1R) & (S-1L). The failure load was increased by 4% and 18.8%, respectively, compared to the control specimen. The enhancement of the steel anchorage of the inclined flexure reinforcement shows higher shear capacity. 7. The overestimation in the finite element analysis's failure load was (1-6%). 8. Ansys has been found to provide good accuracy for predicting the failure load of dapped end beams.

7.3 Recomendations for Future Work The current project focused primarily on the reinforcement details of dapped-end beams with the static vertical load.

The following recommendations are suggested for future researches: 1. The research program may be extended to study the effect of the horizontal load, such as: i) The shape of the dapped end. ii) The combined horizontal & vertical zone is located along the span. 2. Studying the behavior of the dapped-end beams under the effect of torsion. 3. Using prestressed strands in the beam design.