This paper presents results of an experimental study to determine the instantaneous and long-term transfer length of identical fiberglass and steel pretensioned concrete specimens. Seven 6 x 4 in. (102 x 152 mm) specimens were pretensioned using two concentric 3/8 in. (9.5 mm) S-2 glass epoxy strands. In addition, five specimens were pretensioned using a single concentric 1/2 in. (12.7 mm) steel strand. Load cells were used to monitor the jacking force and strain gauges were used to record strain variation in the specimens. The results of the instantaneous transfer length are presented, along with those determined after 20 months. The results show that fiberglass has better bond characteristics and interlock than steel at transfer, although long-term deterioration in bond is proportionately greater in fiberglass. The experimental transfer length was found to be 10 to 11 in. (254 to 279 mm) for the fiberglass prestressed concrete specimens, corresponding to 28 times the nominal diameter of the tendon. The transfer length for identical sized strands stressed at the same level is smaller for fiberglass as compared to steel. A comparison of test results between fiberglass and steel specimens indicated that the Cousins et al. model can also be used to predict the transfer length in fiberglass.
