Análise da fadiga em pontes ferroviárias de estrutura metálica

Abstract

Rail transportation plays a strategic role in the Brazilian logistics network, and steel railway bridges, many of which were designed during the twentieth century and remain in service, are subjected to a high number of repeated loading cycles that promote fatigue, a progressive and silent deterioration mechanism that is difficult to detect through conventional visual inspection. In this context, a gap was identified in the Brazilian standard ABNT NBR 17245 (2026) – Actions Due to Railway and Metro-Rail Vehicle Traffic on Bridges, Viaducts, and Other Structures, which is limited to recommending the Palmgren–Miner rule without providing detailed methodological guidelines for determining the stress ranges required for its application to railway structures. Accordingly, this study aimed to evaluate the remaining fatigue life of the steel truss railway bridge spanning the Urussanga River, located in the state of Santa Catarina, Brazil, and operated by Ferrovia Tereza Cristina, through numerical modeling and cycle-counting methods. To this end, a three-dimensional numerical model of the structure was developed in SAP2000 based on the Finite Element Method (FEM). The passage of four standard train load models (TB240, TB312, TB376, and TB416) was simulated to obtain the stress-time histories of the critical structural members. These data were subsequently processed using the Rainflow counting algorithm and evaluated according to the Palmgren–Miner cumulative damage rule in conjunction with the S–N curves established by AREMA (2010) – American Railway Engineering and Maintenance-of-Way Association, an internationally recognized North American technical standard for the design, analysis, and assessment of steel railway structures, and by ABNT NBR 17245 (2026). The results identified the most fatigue- critical structural member, with estimated remaining fatigue lives varying considerably according to the train load model considered, namely 469 years for TB240, 78 years for TB312, 53 years for TB376, and only 2 years for TB416. It is concluded that the proposed methodology provides a robust technical framework for assessing the structural integrity of aging steel railway bridges by addressing the identified regulatory gap through the integration of the procedures established in ABNT NBR 17245 (2026), AREMA (2010), and the Rainflow counting algorithm.