Fatigue strength of cold-worked non-prestressed reinforcement in prestressed concrete beams

Fourteen identical beams with limited prestress were tested to fatigue failure under different ranges of cyclic loading and the results used to derive the modified Goodman diagram for a 10 mm cold-worked deformed bar acting as non-prestressed reinforcement. The diagram was checked against the results of tests of two beams with different amounts of reinforcement and prestress. Two further beams which were tested under service loading conditions had not failed nor developed excessive deflection or width of cracks after 2 million cycles of load. The implications of the results for the design of ‘Class 3’ prestressed concrete members are discussed.