Fatigue Tests of Pre-Tensioned Prestressed Beams


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Title: Fatigue Tests of Pre-Tensioned Prestressed Beams

Author(s): A. M. Ozell and E. Ardaman

Publication: Journal Proceedings

Volume: 53

Issue: 10

Appears on pages(s): 413-424

Keywords: no keywords

Date: 10/1/1956

Fatigue tests were conducted to determine the behavior of pre-tensioned concrete beams prestressed with ‘I/16-in. seven-wire strands. Eight beams, 6 in. x 8 in. x 20 ft, with a center load, were tested to obtain some solutions to the following questions: Is the use of 7/16-m. seven-wire strand feasible from the standpoint of repetitive loads? Does a beam pre-tensioned with 7/16-in. strand fail in fatigue because of bond failure in the concrete or by breaking in the strand? What is the magnitude of changes in the load-deflection characteristics influenced by fatigue damage ? What amounts of permanent set does a beam undergo when subjected to repetitive loads? Pilot test results indicated that: (1) the use of 7/16-in. seven-wire strands is feasible; (2) the failure of the beams was due to the breaking of wires in the strands by fatigue; (3) load-deflection relationship was affected slightly during the first. 30,000 cycles but greatly just prior to failure of the beam; (4) the permanent set was also small at first but increased appreciably just before failure. Results further indicated that no shear cracks were developed near the supports during the fatigue tests. It was possible to-draw a load versus failure cycle diagram from the data obtained in these tests.