Effects of Cyclic Fatigue Loading on Partially Prestressed Beams - Phase 2

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This is the second of a two-part research investigation of the behavior and modeling of partially prestressed concrete beams subjected to cyclic fatigue loading. Partially prestressed beams are defined here as concrete beams reinforced with a combination of prestressed and non- prestressed reinforcement, designed to allow cracking under full service load (dead plus live load). The following aspects of fatigue will be investigated: the fatigue life of the members, cracking and crack width increases under fatigue, and deflection and deflection increases with the number of cycles of loading. The first phase of the research dealt with rectangular sections tested under constant amplitude fatigue loading. The second phase deals with T sections under variable amplitude fatigue loading simulating real live loads on bridges. The research comprises an experimental and an analytical program. The experimental variables include three levels of reinforcement and, for each, four levels of partial prestressing which include the two boundaries of full reinforcing and full prestressing. The total experimental program and the measurements to be recorded are designed to provide a comprehensive data base on cracking deflections, and their increases with cyclic fatigue loading. The analytical program to predict crack widths and deflections under fatigue is designed to generate rational models that remain valid at the boundaries, represented by fully reinforced and fully prestressed concrete.