Abstract
Glass Fibre-Reinforced Polymers (GFRPs) are a popular option for pedestrian bridges over railway lines as they cause little disruption for installation or maintenance. However, as they are typically lighter and less stiff than traditional materials there is concern about their dynamic response due to human induced actions and train buffeting. Due to a lack of experimental information, further data is needed if such bridges are to be used on future lines, especially with higher speed limits. This paper presents an experimental investigation of the response of a 14.5 m GFRP truss bridge due to pedestrian loading and train induced vibrations. Vibration modes of interest were identified from impact hammer tests. The vibration responses to a range of human loading scenarios, as well as multiple train passes, were measured. The vibration levels remained low under all conditions, demonstrating that this particular type of GFRP bridge is suitable for railway crossings and that further optimisations may be available to designers while meeting vibration serviceability limits. However, consideration of the loadings suggests GFRP bridges may be more susceptible to higher pedestrian harmonics than traditional structures, and that vibrations from train buffeting are likely to be a design consideration for future bridges over high speed lines.
Highlights
Glass Fibre Reinforced Polymer (GFRP) composites are an increasingly attractive construction material when it comes to building pedestrian bridges over railway lines
Due to the low density and relatively low stiffness compared to traditional materials, GFRP bridges could potentially suffer excessive vibrations when exposed to dynamic loading [2]
Much work has considered the effect of railway induced vibrations from high speed trains as they travel on bridges [12,13], there exist only limited investigations into the response of GFRP bridges located over railway lines [14,15,16]
Summary
Glass Fibre Reinforced Polymer (GFRP) composites are an increasingly attractive construction material when it comes to building pedestrian bridges over railway lines. Much work has considered the effect of railway induced vibrations from high speed trains as they travel on bridges [12,13], there exist only limited investigations into the response of GFRP bridges located over railway lines [14,15,16] These have highlighted the concern designers have in using lightweight materials, like GFRPs, in such locations, and the difficulty in predicting vibration responses due to train buffeting. While recent work, such as Drygala et al [4], has applied current guidelines to numerical models of theoretical GFRP structures, including human and train induced vibration, there is still a lack of experimental data to validate both structural and loading models. Further analysis was performed to evaluate the bridge response to human and passing train dynamic loading and critically evaluate the suitability of some existing design guidance and recommend improvements
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