Abstract Dynamic effects caused by vehicles on bridges is a key aspect to consider on the designing, monitoring and maintenance of the roadway infrastructure. This is particularly important in the case of modular truss bridges as they face operational restrictions when spans lengths are larger than 60 m. In the recent years, new efforts are being directed to develop fully-functional modular steel bridges of substantially larger spans. For this purpose, it is essential to fully understand the dynamic effect of vehicles on such structures. This paper provides a detailed study on two modular steel bridges considering span lengths from 120 to 140 m. A 3D coupled vehicle-bridge model is used to simulate the vehicle-bridge interaction and evaluate the dynamic load allowance of the structures. Different profiles of road irregularities are generated and their influence is investigated. The results reveal the importance of defects that excite vertical bouncing modes of the vehicle. The effects of considering different span lengths and vehicle speeds are also discussed. Finally, the dynamic load allowance obtained for the bridges under study is compared to that calculated with the expressions given in several design codes.
In the present contribution the effect of the continuity of the ballasted track on the dynamic response of simply-supported railway bridges composed by structurally independent adjacent slabs at each span is addressed.Previous research works and experimental campaigns performed on simply-supported structures have shown that the presence of the ballast layer and other track components (rails, sleepers) may induce a dynamic coupling effect between the bridge spans or adjacent decks.In this study the influence of this effect on the train-induced vibrations is assessed.With this purpose a preliminary three-dimensional finite element (FE) model that includes the track components as a set of discrete mass, stiffness and damping elements has been implemented to numerically evaluate the influence of the continuity of the track components on the prediction of the bridge acceleration response under the passage of railway vehicles.The numerical model is calibrated with the load test results performed on a simply-supported railway bridge composed by several adjacent slabs.Finally the measured structural response of the bridge under train induced vibrations is compared with the numerical predictions.Preliminary conclusions regarding the importance of considering the continuity of the track components for the prediction and the assessment of the Serviceability Limit State of vertical acceleration in ballasted simply-supported railway bridges are presented.
Predicting the dynamic response of portal frame bridges is challenging because of the strong influence of the soil-structure interaction.This aspect adds complexity to the vibratory phenomenon, and, as a result, accurate numerical analyses are difficult to conduct and time-consuming.For this reason, the soil-structure interaction mechanism is seldom considered in the numerical models.However, as evidence shows, this constitutes an important source of discrepancy between numerical and experimental results.In this investigation, a study on an existing portal frame railway bridge is carried out.First, the identification of its modal parameters from experimental data is addressed.Then, a 3D finite element numerical model considering the track-bridge-soil system is implemented.Perfectly matched layers are considered at the model boundaries.The soil-structure interaction is evaluated and the results are used to implement a simplified model, on which the soil is substituted by a series of spring-dampers.After calibration, an experimental-numerical comparison is performed on the bridge 1
