An Exploratory Study of Shear Fatigue Behavior of Prestressed Concrete Girders

T he use of pretensioned concrete beams in bridge superstructures has increased dramatically in the past 30 years. At the same time, strength reduction factors and load limits have been increased, effectively reducing load margins for existing bridges. As a result, the limit state of fatigue failure is now a more important consideration in the evaluation of existing bridges and the design of new bridges. At the present time, engineers have few guidelines to follow for fatigue design of pretensioned concrete members. This paper describes the results of an exploratory investigation undertaken in the Phil M. Ferguson Structural Engineering Laboratory at The University of Texas at Austin to gain a better understanding of the shear frtigue behavior of pretensioned concrete girders. At present, little experimental research has been conducted on shear fatigue. The authors are unaware of any previous shear fatigue tests on full scale specimens designed according to present design specifications. The present investigation was very limited in scope, involving tests of only three full scale girder specimens. Obviously, the wide range of variables actually present in pretensioned bridge girder usage could