Serviceability assessment of a pedestrian bridge: Concrete vs. GFRP composite deck

In the paper the dynamic analysis and the assessment of the dynamic behaviour of a three-span cable-stayed pedestrian bridge was carried out. Two variants of the footbridge deck were analyzed: the concrete deck and the deck made of glass-fibre-reinforced polymers (GFRP). Firstly, the natural frequencies and modes of vibration for both variants were calculated. Then, vibrational comfort criteria for a single pedestrian running for both variants of the deck were assessed. It occurred that in the case of the concrete deck the first natural frequency was located in the range of the typical vertical vibrations caused by a single pedestrian running. Moreover, the risk of resonance was assessed as 'medium'. Hence, dynamic response of the footbridge to a single runner was performed. This further analysis revealed that the vertical comfort criteria were not exceeded and the comfort level of use was classified as a 'maximum'. In the case of the GFRP composite footbridge deck, the first natural frequency was situated outside the frequency range typical for vibrations caused by pedestrians. On the basis of the results, the risk of a resonance phenomenon for the structure with the GFRP deck was ruled out. Thus, further dynamic analysis of the footbridge exposed to loading generated by pedestrians was unnecessary.