Relaxation Characteristics of Prestressing Strand

Relaxation characteristics of seven-wire prestressing strand were studied in this experimental investigation. Tests were conducted on both stress-relieved strand and low-relaxation strand. Two series of tests were carried out on both types of strand.. First, strand specimens were tested under conditions of constant strain. Second 3 stress in the strand specimens was reduced at a time of 24 hours after the initial tensioning3 then held at the strain accompanying their reduced stress for the remainder of the test. A quadratic equation was developed to predict losses of stress due to relaxation. The effects of stress reduction were accounted for by the use of a load reduction variable included in the quadratic equation