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Fatigue assessment of a reinforced concrete railway bridge based on a coupled dynamic system

Abstract This article proposes a method for assessing fatigue damage in reinforced concrete bridges based on a train-bridge coupled dynamic analysis system. The analysis system can be used to perform coupled vibration analyses of the bridge’s behavior during train passages. The Palmgren–Miner rule is used to estimate the linear accumulation of fatigue damage based on recommended S–N relationships for reinforced concrete from various codes. The method can be used to evaluate the dynamic performance of a bridge in conjunction with moving load (ML) and moving spring-mass-damper (MSMD) vehicle models. Calculated dynamic stresses are used to evaluate the fatigue damage at critical locations. A case study is presented focusing on the Långforsen Bridge, a railway arch bridge with a span of 89 m in northern Sweden. Fatigue assessments are conducted by combining the presented method with empirical measurements, and the effects of train speed and axle load on fatigue damage are investigated. Train-bridge coupled dynamic analysis using the proposed method provides a feasibly accurate solution for fatigue damage prediction in the four studied load cases. For low speeds and light loads, the two vehicle models yielded identical predictions of cumulative fatigue damage. However, their predictions diverged significantly for higher speeds and/or axle loads.