Acknowledgements

advanced international standards and design guidelines. However, the numerical estimation of the dynamic response of footbridges obtained according to these codes differs from the

In order to overcome this problem, a new generation of crowd-structure interaction models, that constitute a new modelling framework, has been proposed by the scientific community. All these models share, as common characteristic, that they simulate the crowd-structure interaction phenomenon using two sub-models: (i) a pedestrian-structure interaction submodel and (ii) a crowd sub-model. For the first sub-model, the pedestrian is modelled by a SDOF, MDOF or IP system and the structure via its modal parameters obtained from a finite element model. For the second sub-model, the last tendency is to use a multi-agent method based on the principles of the social force model. The linking between the two sub-models is achieved by the inclusion of several behavioural conditions in the model. Comfort and lateral lock-in threshold are usually considered. Three key aspects are taken into account for this new modelling framework: (i) the inter-and intra-subject variability, (ii) the pedestrian-structure interaction and (iii) the crowd dynamics. The last two aspects are guaranteed by the own formulation of the model, and the first is ensured assuming that the different parameters of

One of these new crowd-structure interaction models has been described briefly in this chap-

Finally, the potential of this new modelling framework has been illustrated with a case study, the analysis of the lateral lock-in phenomenon of the Pedro e Inês footbridge (Coimbra, Portugal). As result of this study, a good agreement is achieved between the number of pedestrians which originates the lateral instability phenomenon obtained during the experimental test and the numerical estimation determined via the crowd-structure interaction

Although the use of the crowd-structure interaction model allows improving the estimation of the response of footbridges under pedestrian flows, further studies are being conducted in order to better characterize some aspects of these models. Among others, the following

i. The crowd-structure interaction model might be generalized to longitudinal direction via

ii. In order to better characterize the inter- and intra-subject variability, the statistical distributions that characterize the parameters of the pedestrian-structure interaction model should be improved via the analysis of the behaviour of other groups of pedestrians on

iii. The relationship between the parameters of the pedestrian-structure interaction model

the estimation of the parameters of the SDOF-system in that direction.

and the step frequency of the pedestrian should be further analysed.

value recorded experimentally.

78 Bridge Engineering

model.

9. Future trends

research lines may be cited:

different types of footbridges.

the crowd-structure interaction model are random variables.

ter, emphasizing the section corresponding to the crowd behaviour.

This work was supported by the Ministerio de Economía y Competitividad of Spain and the European Regional Development Fund under project DPI2014-53947-R.
