Push-Off Tests in the Study of Cyclic Behavior of Interfaces between Concretes Cast at Different Times

The knowledge about the cyclic behavior and effects of fatigue on interfaces between concrete cast at different times, subjected to shear stress, is still very limited. This aspect is particularly relevant in structures subjected to important cyclic loads, such as railway bridges. In this context, first, a brief state of the art on the monotonic and cyclic behavior of interfaces between concretes cast at different times is presented. Then, the test campaign, which was aimed at obtaining experimental support for modeling the behavior of such interfaces, subjected to a high number of load cycles, is described, and the corresponding results are discussed and analyzed in terms of slip and crack opening, stress variations in the monotonic tests, failure mode, and number of resisting load cycles. It was further observed that the number of resisting load cycles increases as the maximum load level decreases. On the basis of this evidence, an experimental S-N curve was set for this type of interface. (C) 2015 American Society of Civil Engineers.