Modeling of bridges for accurate estimation of remaining service life

The overall aim of the project is to optimize the maintenance of steel railway bridges in Norway. Because many such bridges are quite old, their initial design did not account for modern axle loads and train speeds, nor fatigue limit states. However, replacing all old bridges is not feasible due to the immense construction cost, train service disruption, and environmental impact. Additionally, many of these bridges are still structurally sound. To calculate the remaining service life of these bridges, finite-element models have been established. The accuracy of a remaining service life calculation is dependent on the accuracy of the model.

A test case for this project is Lundamo railway bridge, located over the Sokna river south of Trondheim. Finite-element models of this steel open-deck truss bridge have been developed. To test the accuracy of these models, strain gauges have been affixed to both the structural components of the bridge and the running rails. Strain measurements from train passages over the bridge are collected via these strain gauges, which can then be converted to stresses and compared to the model-predicted values to determine the error in the models. The strain gauges on the structural components measure the structural response of these components to loading, and the strain gauges on the running rails measure axle loads and train speeds, allowing for detection of the type of train that corresponds to each recorded passage.

These field measurements are collected for the purpose of improving the accuracy of existing finite-element models. By considering the effects of fatigue loading, the project will improve the accuracy of prediction of remaining service life by analyzing the ability of finite-element models to predict the response of bridges to train loads.