Probabilistic analysis of transmission and anchorage lengths in prestressed concrete elements: evaluation of model uncertainties and coefficients for a reliability-based design

Transmission and anchorage lengths are important parameters in the design of pretensioned reinforced concrete members, and according to the main design codes, semi-empirical models are adopted to estimate their values. The aim of this study is to investigate the reliability of the 2nd generation Eurocode 2 (2023) and fib Model Code 2020 prescriptions and thus propose new coefficients to consider the model uncertainties. For calibrating model uncertainty distributions for both transmission and anchorage lengths, two extensive databases of experimental measures from the existing scientific literature have been collected, respectively of 951 and 405 samples, furtherly filtered for obtaining two homogeneous sets of 561 and 224 experimental observations. Results show that the prestress force release methodology strongly affects the model uncertainty distributions for both transmission and anchorage lengths. Finally, new probabilistic coefficients are proposed to adjust the codes’ formulations and ensure the achievement of suitable target reliability lengths to be adopted in design situations.