ABSTRACT
During visual inspection of Fumaça Waterfall bridge, systematic cracks were identified on I section beams of the deck’s support structure. Fumaça Waterfall bridge is the single steel bridge on the Ferrovia do Aço Railway. Located between two tunnels this bridge is one of the strategic bridges for the railway considering the difficulty of access to accomplish any repair on its structure. Because damage has such a broad reach an emergency procedure was adopted, including reduction of train’s speed, study of mechanisms of cracks formation to provide an emergency action and to assist a reinforcement design. The mechanisms of cracks formation were investigated by means of monitoring and simulations on finite element models.
Dynamic tests were accomplished on bridge structure before of the cracks’ identification. An instrumented train, with loads in accordance with loads frequently transported by the railway, was used as excitation force to the structure. The bridge was instrumented with servo-accelerometers and strains gages installed in the top chords, bottom chords an end posts of main trusses of the structure. Structural monitoring during train’s passages under controlled speeds was accomplished and data collected were suitable to determine modal shapes, dynamic and static effects on the structure for each train’s speed. This way a calibrated F.E.M. was developed to make a diagnosis about the cracks and stablish corrective actions to be taken.
To increase remaining-life of structure to more than 50 years, fatigue study was done using a hybrid method based on F.E.M. values and experimental values. In the following, a reinforcement design based on the redistribution of forces over under-track structure was proposed. This reinforcement restores structure durability to more than 50 years.
To help railway administrator in the decision of limiting speeds, remaining-life for the joists in current state was calculated for operational speeds of the train. Strain rosette installed on the web of the longitudinal joist to define corrective actions. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig215_1.jpg"/>
From this analysis, it was possible to define the limit of the train velocity of 40 km/h, which is considered acceptable by operational division of the concessionaire and also gives enough time to reinforcement execution.
