Fatigue assessment of a high-speed railway composite steel-concrete bridge by the hot-spot stress method

Abstract

Purpose The purpose of this paper is to investigate the fatigue performance of a welded detail from a composite steel-concrete railway twin girder bridge caused by a passenger train circulating at varying speeds, by identifying the dynamic amplification scenarios induced by resonance. For this purpose, the hotspot stress method is used, instead of the traditional nominal stress methods. Design/methodology/approach This paper assesses the fatigue behavior of a welded connection considering critical stress concentration locations (hotspot). Finite element analysis (FEA) is applied, utilizing both a global and a local submodel, made compatible by displacements field interpolation. The dynamic response is obtained through the modal superposition method. Stress cycles are extracted with the rainflow counting method and the fatigue damage is calculated with Palmgren-Miner’s rule. The feasibility of five submodels with different mesh densities, i.e. 1, 2, 4, 8 and 20 mm is verified. Findings An increase in the fatigue damage due to the resonance effect was found for the train traveling at a speed of 225 km/h. A good agreement between the computed fatigue damage for the submodels is achieved. However, a non-monotonic hotspot stress/fatigue damage vs mesh density convergence was observed with a peak observed for the 4 mm model, which endorses the mesh sensitivity that could occur when using the surface stress extrapolation detailed rules specified in the standards for the hotspot stress method. Originality/value Advanced dynamic analyses are proposed to obtain local stresses in order to apply a local method for the fatigue assessment of a bridge’s structure subjected to high-speed railway traffic on the basis of the mode superposition technique resulting in much less computing times.

Train–track–bridge dynamic interaction: a state-of-the-art review

“…[150], based on the stress range and its cycle count of each train passage were obtained by dynamic analysis, the fatigue reliability was achieved by solving a fatigue limit-state function through the S-N approach. Such work enabled the discussion of the residual service life of a bridge [151] and the investigation of fatigue behaviour in the weak part of a bridge such as the welded connection of a composite steel-concrete railway girder bridge [152].…”

Fatigue assessment based on hot-spot stresses obtained from the global dynamic analysis and local static sub-model

“…Some aspects of fatigue are especially pertinent to bridges of metallic and composite structures of steel and concrete (Nussbaumer et al, 2011). The dynamic loads due to high-speed train passage can cause dynamic amplification and thus increase fatigue damage (Alencar and Ferreira, 2018).…”

“…The global model was developed in shell elements, whereas the sub-model was developed in solid elements. Fatigue assessments in a critical detail in the "Alcácer do Sal" railway structure were performed by Alencar and Ferreira (2018) and Ferreira (2017). Fatigue evaluation of a critical connection of the historical bridge Hercílio Luz, located in "Florianópolis", Brazil, was performed by Liu et al (2019) through the global-local methodology.…”