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.

The structural response of reinforced concrete slabs in railway bridges is strongly influenced by local dynamic effects and, therefore, detailed calculations of internal forces have to be performed for a realistic fatigue assessment. In this context, this paper discusses the influence of track irregularities and modal damping coefficients in the dynamic response and fatigue behaviour of a railway bridge deck slab. For that purpose, track irregularities were measured (at different instants of time) and damping coefficients were determined based on acceleration records for passing trains in a real bridge. The bridge behaviour was calculated using a train–bridge interaction methodology, considering calibrated numerical models of the viaduct and the train. The fatigue damage was quantified through the linear damage accumulation method. This methodology allowed to understand the way track irregularities and damping coefficients affect the magnitude of applied bending moments and fatigue damage in the slab.

Continuous bridge decks constructed with precast girders undergo significant stress changes caused by the concrete delayed deformations because of creep and shrinkage. These effects must be taken into account in the design of new structures. The validation of the analysis procedures should ideally be carried out through the comparison between the calculations and the results observed in real structures. However, experimental results of the construction and long-term behavior of these structures are scarce. The construction of a major bridge in Portugal has provided the opportunity to monitor one such structure. This paper presents the monitoring campaign and the analysis strategy that was developed to assess the long-term variation of strains and stresses in precast continuous bridges. The numerical analysis was validated by comparison with the results observed in the real bridge. The consequences of carrying out simplified analyses based on limited information about the concrete properties and the constr...