Estudo do comprimento de transferência em peças de concreto protendido

Abstract

Towards the lack of consensus regarding the transfer length, his research studies the bond of reinforcements in our market, aiming to clarify their behavior concerning bond and the transfer of prestressing force. The results of the investigations are presented in two parts, theoretical and experimental, on the bond of seven-wire strands with a diameter of 15.2 mm, pre-stressed and pre-bonded in C45 strength class concrete. The first part consists of a theoretical analysis of the determination of the transfer length. For this purpose, analytical models already established in the current literature and technical standards NBR 6118 (2014), ACI 318 (2019), FIB MODEL CODE (2010), and EUROCODE 2 (2004) were used. The second part of the research consists of three laboratory tests conducted at the Civil Engineering Laboratory of the State University of Rio de Janeiro (UERJ). The test method adopted was the ECADA Method, which is divided into three parts: (1) prestressing and concreting, (2) measurement of the transfer length of the beams during the prestressing removal operations, and (3) pull-out tests and analysis of strand slip as a function of prestressing force variation, in which bond stress was studied. The experimental results were compared to the theoretical results, allowing us to evaluate the behavior of prestressing force and the calculation of the transfer length in pre-stressed concrete members. For the tests conducted, it was possible to measure the transfer lengths, which showed values lower than those predicted by the standards, indicating that they favor safety.