A New Smoothing Technique for Transfer-Length Determination

[EN] Transfer length is a significant parameter in the design of pretensioned concrete members. This study reports the measured transfer length of 15.2 mm (0.6 in.) prestressing strands. Twenty-four pretensioned concrete beams were cast using conventional concrete. The compressive strength at release ranged from 27 to 65 MPa (4000 to 9500 psi). Transfer lengths were determined by measuring concrete surface strains and using the average maximum strain (AMS) method. A new technique was developed to smooth the measured concrete surface strains. The measured transfer lengths were compared to the predicted transfer lengths using ACI 318-14 and AASHTO-LRFD equations. The results indicate that the proposed smoothing technique provides better results than the current threepoint moving average technique. The current code equations are conservative to predict transfer length for pretensioned concrete members having concrete compressive strength at release greater than 27 MPa (4000 psi).