Dynamic behaviour of a GFRP-steel hybrid pedestrian bridge in serviceability conditions. Part 2: Numerical and analytical study

The Part 2 of this two-part paper reports numerical and analytical studies concerning the serviceability dynamic behaviour under dynamic human loads of a typical GFRP-steel hybrid girder system for pedestrian bridges. These studies, which focused on the recent St. Mateus footbridge (Portugal), had two main objectives: (i) to assess the ability of conventional numerical models and analytical formulae to simulate the vibration behaviour of GFRP-steel hybrid footbridges; and (ii) to complement the observations and measurements made in the experimental campaign (Part 1), thus providing in-depth understanding of the vibration performance of this type of footbridges. First, a finite element (FE) model was developed and calibrated with the static and modal experimental data. Then, the FE-model was used to evaluate the vibration response of the footbridge for the same pedestrian activities induced in situ. The design formulae available in the literature for predicting the maximum acceleration of structural systems are also reviewed and were applied to evaluate the resonant response of the footbridge for both single and crowded conditions of pedestrian traffic. The results obtained confirmed the adequate structural behaviour of the St. Mateus footbridge under real dynamic (human) pedestrian load cases and show that this innovative GFRP-steel hybrid structural solution is suitable for pedestrian bridges. The results of the different investigations reported in this paper also showed that both numerical and analytical approaches are able to predict the vibration response of GFRP-steel hybrid footbridges with reasonable accuracy.