Experimental Investigation on the Effect of Time on Transfer Length in Pre-Stressed Concrete Beams

Abstract

Abstract The effect of time on of transfer length variations in prestressed concrete elements has not been addressed in the current design codes of practice. The present investigation examines the effect of different parameters on transfer length over time. Therefore, a number of 13 pretensioned concrete beams were made in the laboratory with differences in beam cross-section and length, strand number and arrangement, concrete cover, and strand eccentricity. The 95% AMS technique was used to calculate transfer length. The results showed that transfer length of all beams increases over time, the highest measure was experienced between 14 and 28 days after strand detensioning. This value ranged between 2 and 5% in single-strand beams, and 12 to 14% in 10-strand beams. It was concluded that strand eccentricity has no considerable effect on the transfer length variations. The beam live end captured higher transfer lengths in most of the beams; however, strand arrangement and the amount of concrete cover were found to have the potential to shift higher transfer lengths to beam dead end. It was also revealed that beam length plays a significant role on transfer length, while longer beams featured larger transfer lengths. The percentage of increase in the transfer length in 10-strand beams after 14 days reached approximately twice that of the single-strand counterparts. The reason was associated with the number of strands, cross-sectional dimensions, and strand arrangement.