Evaluation of prestress losses in concrete beams using destructive and non-destructive methods

Over the past few decades, prestressing techniques have become essential in the construction of key structures, infrastructure, and bridges. The serviceability and safety of prestressed concrete (PC) elements are closely tied to the effectiveness of the prestressing process. As a result, significant efforts have been made to develop accurate tools and methods for estimating prestress loss that can occur during service life in relation to effects of tendon relaxation, concrete creep and shrinkage, and parameters of real environment such as, for example, temperature and relative humidity. Among techniques, static identification using saw-cut method and strain measurements has been improved to achieve accurate and reliable results in terms of prestress loss evaluation. This paper represents an experimental campaign carried out on PC beams of different ages. A comparison between the modified saw-cut method, based on strain measurements during saw-cut operations, and the destructive cracking method has been performed. The attention is focused mainly on calculation of stresses and strains in the notch of saw-cut, considering the intensification factors according to Neuber theory, to analytically detect prestress losses. Concluding remarks, including future research directions, will be presented at the end of the paper.