In the recent years, an increasing number of studies are being developed in order to assess the dynamic response of structures induced by human loading. Among them, stadia or sports arenas are of particular interest, because of the presence of active people during matches and concerts, that can lead to high levels of vibrations on the grandstands. To deal with these problem and guarantee safety during events, it is important to estimate the response generated in the structure by crowd activities. However, the prediction of the force induced by the motion of a large crowd is still a challenging issue if one considers its stochastic behaviour. Thanks to its ability to provide full-field displacements and strains given a sequence of images, Digital Image Correlation (DIC) can be a valid solution for crowd loading estimation. In this work, a detailed study of Digital Image Correlation is proposed in case of images acquired during events like concerts or football matches. A sensitivity analysis is performed to evaluate the effect of the most relevant DIC parameters on image correlation results. Some values are recommended, both in terms of camera settings and software programming, to be used for future works involving this type of applications. Given a sequence of frames representing the crowd motion, the proposed technique provides to involve DIC to calculate the displacement time history of the moving people and then to use it to estimate the force induced in the hosting structure. In order to validate this approach on a realistic case study, an experimental activity was carried out on a grandstand of the Giuseppe Meazza stadium in Milan. A group of 30 volunteers was asked to jump synchronously to the beat of multiple songs, forcing the structure. Digital Image Correlation was used to record the different scenes and estimate the relative loading. Since the Frequency Response Function (FRF) of the grandstand was available, it was possible to perform an estimation of the acceleration levels of the structure due to such loading conditions. These values of accelerations are finally compared with the ones measured by the accelerometers mounted on the grandstand, providing very similar results, as evidence of the effectiveness of the technique.
Negli ultimi anni sono stati effettuati numerosi studi riguardanti la risposta dinamica delle strutture indotta dal forzamento prodotto da attività umane. Tra questi, gli stadi hanno destato particolare interesse, per via della partecipazione attiva da parte degli occupanti durante concerti o partite, che possono indurre elevati livelli di vibrazione nelle tribune. Al fine di considerare questo tipo di problemi e di garantire la sicurezza durante gli eventi, è importante stimare la risposta vibratoria prodotta dalla tribuna in seguito ad attività da parte del pubblico. Tuttavia, nel caso di una folla di grandi dimensioni, questo compito diventa molto difficile, soprattutto se si considera la natura stocastica del comportamento assunto dalla folla stessa. Grazie alla sua capacità di fornire campi di deformazione e di sforzo partendo da una sequenza di immagini, la Digital Image Correlation (DIC) può essere utilizzata come valida soluzione per la stima del forzamento del pubblico. In questo lavoro viene presentato uno studio dettagliato riguardante l’utilizzo della tecnica Digital Image Correlation applicata ad immagini provenienti da eventi quali concerti o partite di calcio. È stata condotta un’analisi di sensitività per studiare gli effetti dei parametri più rilevanti della DIC sui risultati finali di correlazione tra le immagini. Sono stati suggeriti alcuni valori ottimali, sia in caso di specifiche della telecamera che di programmazione software. Data una sequenza di immagini che rappresenta il moto del pubblico, la tecnica proposta prevede l’utilizzo della DIC per calcolare la storia temporale dello spostamento della folla e poi di usarla per stimare il forzamento introdotto nella struttura. Per poter validare questo approccio in un contesto realistico, è stata effettuata un’attività sperimentale su una tribuna dello stadio Giuseppe Meazza di Milano. È stato chiesto a un gruppo di 30 volontari di saltare a ritmo di varie canzoni, ai fini di rappresentare diverse condizioni di carico. Nota la funzione di risposta in frequenza (FRF) della tribuna, è stato possibile stimare i livelli di vibrazione della struttura prodotti dall’eccitazione introdotta. Questi valori di accelerazione sono stati poi confrontati con quelli degli accelerometri installati sulla tribuna, fornendo risultati molto simili e giustificando quindi l’efficacia della tecnica adottata.
Structural dynamic analysis by means of digital image correlation estimation of crowd induced loading
CARRERA AVIN, NEREA;RUIZ VIVANCO, MIGUEL
2019/2020
Abstract
In the recent years, an increasing number of studies are being developed in order to assess the dynamic response of structures induced by human loading. Among them, stadia or sports arenas are of particular interest, because of the presence of active people during matches and concerts, that can lead to high levels of vibrations on the grandstands. To deal with these problem and guarantee safety during events, it is important to estimate the response generated in the structure by crowd activities. However, the prediction of the force induced by the motion of a large crowd is still a challenging issue if one considers its stochastic behaviour. Thanks to its ability to provide full-field displacements and strains given a sequence of images, Digital Image Correlation (DIC) can be a valid solution for crowd loading estimation. In this work, a detailed study of Digital Image Correlation is proposed in case of images acquired during events like concerts or football matches. A sensitivity analysis is performed to evaluate the effect of the most relevant DIC parameters on image correlation results. Some values are recommended, both in terms of camera settings and software programming, to be used for future works involving this type of applications. Given a sequence of frames representing the crowd motion, the proposed technique provides to involve DIC to calculate the displacement time history of the moving people and then to use it to estimate the force induced in the hosting structure. In order to validate this approach on a realistic case study, an experimental activity was carried out on a grandstand of the Giuseppe Meazza stadium in Milan. A group of 30 volunteers was asked to jump synchronously to the beat of multiple songs, forcing the structure. Digital Image Correlation was used to record the different scenes and estimate the relative loading. Since the Frequency Response Function (FRF) of the grandstand was available, it was possible to perform an estimation of the acceleration levels of the structure due to such loading conditions. These values of accelerations are finally compared with the ones measured by the accelerometers mounted on the grandstand, providing very similar results, as evidence of the effectiveness of the technique.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/154139