Correlation of Strand Surface Quality to Transfer Length

Strand bond depends on numerous factors, such as concrete properties and strand surface condition. The strand s surface may contain different types and amounts of lubricants and residual films from the manufacturing process. These can reduce the bonding capacity of the strands. Additionally, the amount and type of lubricants and residual films vary between strand manufacturers. The strand s transfer and development length is a measure of strand bond performance. However, current building and bridge code equations used to predict transfer and development length do not address bonding capacity of the strand. The Standard Test for Strand Bond (STSB) has been developed to assess the bonding capacity of prestressing strands. Using data collected from literature and beam tests conducted at the University of Arkansas, a prediction equation for transfer length is proposed that incorporates strand bond quality, as determined by the STSB.