The Effect of Confinement on Transfer and Development Length of 0.7 Inch Prestressing Strands

The use of large 0.7 inch prestressing strands is advantageous in the production of bridge girders with superior capacity. The main objective of this research is to study the effect of confinement on transfer and development length of 0.7 inch strands in prestressed I-girders. Factors affecting transfer and development length are presented. Prestressed prismatic specimens were fabricated using different levels of confinement. Transfer length was measured using DEMEC points. A series of pull-out tests were conducted to investigate the strands development. The conclusions of this research were: 1) AASHTO LRFD specifications conservatively estimates the 0.7 inch strands transfer length. 2) Strand confinement reduces the strands development length. 3) Current AASHTO LRFD equations for development length could be applied when 0.7 in. strands are used.