Post‐tension retrofitting of RC dapped‐end beams: A numerical investigation

Dapped-end beams are frequently used in roofing and flooring systems of precast reinforced concrete buildings as well as in bridge constructions. Due to design flaws, deterioration, and construction mistakes, they may have unsatisfactory structural performance. Past experimental studies investigated the effectiveness of post-tension strengthening techniques applied to dapped-end beams, revealing them as effective solutions, even though a limited range of influencing parameters were considered. This paper numerically investigates the performance improvement provided by post-tension interventions applied to dapped-end beams. Numerical models were built through a refined FEM software simulating two experimental tests found in the literature. After the models' calibration, a post-tension intervention was designed and implemented in the models, considering the level of prestressing as the main intervention's parameter. Afterwards, the behavior in the post-intervention condition was analyzed to find changes in the failure modes and highlight the performance improvement concerning cracking phenomena and ultimate loadbearing capacity. It is found that the level of tendons' prestress significantly improves the cracking load, which increases almost linearly with respect to it. Conversely, the significant gain in terms of ultimate load-bearing capacity (up to 53%) shows only slight variations when the prestress level changes. Finally, accounting also for the reduction of deformation capacity for high prestressing levels, practical suggestions are provided regarding the optimal posttension choice.