The 3D response of a large-scale masonry arch bridge: Performance under high-cycle fatigue loads

This study presents an extensive experimental campaign conducted on a large-scale masonry arch bridge to investigate the damage accumulation and crack propagation mechanism under high-cycle fatigue loading. Five hydraulic actuators were positioned along the longitudinal centre line and then off-centre near the spandrel wall to simulate operational loading conditions experienced by bridges under passing trains. The magnitude of fatigue load was incrementally increased from 50 kN to 190 kN in 20 kN steps after every 172,800 loading cycles (for one actuator), equivalent to continuous loading at 1 Hz for 48 h. In total, over 13.8 million loading cycles were applied by the five actuators on the bridge. Following fatigue testing, the bridge was subjected to different levels of static patch loads, and two failure-level static patch loads applied over the quarter-span and three-quarter span locations of the arch barrel to assess its load-carrying capacity. The three-dimensional responses of both the arch barrel and spandrel walls, observed crack patterns in masonry, stiffness degradation, and the failure mechanism of the arch bridge at different levels of loading are discussed in this paper. The findings provide critical insights into the damage characteristics of masonry arch bridges under fatigue loading and offer a valuable dataset of the bridge’s response for validating both low-fidelity and high-fidelity numerical models.