Light and slender footbridges can be susceptible to excessive vibrations caused by the crossing of humans. This problem prompted the scientific community to develop more accurate methodologies to assess the pedestrian effects on the footbridges. The Streicker Bridge is a pedestrian bridge located on the Princeton University Campus. The footbridge is 104 m long and consists of a main span and four approaching legs. The deck is made of post-tensioned high-performance concrete, and the arch is made of weathering steel. Besides providing pedestrian crossing, this footbridge is instrumented with various Structural health monitoring (SHM) systems. Following the completion of the construction, static and dynamic testing of the structure was conducted. From the experimental campaign, it can be extracted that no vibration modes fall in the frequency interval of 0.5-2.3 Hz that is critical for walking activities. However, a mode was identified to be near 3 Hz, close to the interval critical for running activities (2.5-3.5 Hz). This may lead to excessive vibrations when a group of people run over the bridge. Three finite element (FE) models are presented: Model A is developed in SAP2000 and contains only frame elements; Model B is developed in ANSYS and contains only frame elements; and Model C is developed in ANSYS and its deck is modelled with shell elements. The goal of developing three numerical models is to be consistent in the comparison with the experimental results in terms of static and modal behavior. The FE models are validated by performing a static and a modal analysis. Besides, from the modal analysis it can be deduced that the first five modes of the Streicker Bridge are flexural modes including torsion in some of its members. After the first flexural modes, the following six modes are lateral or lateral/flexural for the three numerical models. Finally, a transient analysis that accounts for a running pedestrian is presented. The moving and time-varying force induced by the pedestrian is modelled according to the sinusoidal approach proposed in Sétra guidelines. The maximum vertical acceleration recorded (0.17 m/s2) is below the threshold of Comfort class CL 1 (0.50 m/s2) in accordance to HiVoSS guidelines.
Le passerelle leggere e sottili possono essere sensibili alle eccessive vibrazioni causate dall'incrocio di esseri umani. Questo problema ha spinto la comunità scientifica a sviluppare metodologie più accurate per valutare gli effetti dei pedoni sulle passerelle. Streicker Bridge è un ponte pedonale situato nel campus universitario di Princeton. La passerella è lunga 104 metri e consiste in una campata principale e quattro gambe in avvicinamento. Oltre a fornire il passaggio dei pedoni, questa passerella è dotata di vari sistemi di monitoraggio strutturale (SHM). Dopo il completamento della costruzione, sono stati condotti test statici e dinamici della struttura. Sono presentati tre modelli a elementi finiti: il modello A è sviluppato in SAP2000 e contiene solo elementi del telaio; Il modello B è sviluppato in ANSYS e contiene solo elementi frame; e il modello C è sviluppato in ANSYS e il suo mazzo è modellato con elementi di shell. L'obiettivo di sviluppare questi tre modelli è di essere certo nel confronto con i risultati sperimentali per quanto riguarda il comportamento statico e modale. I modelli FE sono stati validati eseguendo un'analisi statica e modale. Inoltre, dall'analisi modale si può dedurre che i primi cinque modi del ponte Streicker sono flessionali, inclusa la torsione in alcuni dei suoi membri. Dopo i primi modi flessionali, i seguenti sei modi sono laterale o laterali/flessionali per i tre modelli numerici. Infine, viene eseguita un'analisi transitoria che tiene conto delle forze indotte di un pedone che corre. La forza mobile e variabile nel tempo è stata modellata secondo l'approccio sinusoidale proposto nelle linee guida Sétra.
Numerical assessment of the static and dynamic behavior of the Streicker bridge
LIZANA VILASECA, MARC
2018/2019
Abstract
Light and slender footbridges can be susceptible to excessive vibrations caused by the crossing of humans. This problem prompted the scientific community to develop more accurate methodologies to assess the pedestrian effects on the footbridges. The Streicker Bridge is a pedestrian bridge located on the Princeton University Campus. The footbridge is 104 m long and consists of a main span and four approaching legs. The deck is made of post-tensioned high-performance concrete, and the arch is made of weathering steel. Besides providing pedestrian crossing, this footbridge is instrumented with various Structural health monitoring (SHM) systems. Following the completion of the construction, static and dynamic testing of the structure was conducted. From the experimental campaign, it can be extracted that no vibration modes fall in the frequency interval of 0.5-2.3 Hz that is critical for walking activities. However, a mode was identified to be near 3 Hz, close to the interval critical for running activities (2.5-3.5 Hz). This may lead to excessive vibrations when a group of people run over the bridge. Three finite element (FE) models are presented: Model A is developed in SAP2000 and contains only frame elements; Model B is developed in ANSYS and contains only frame elements; and Model C is developed in ANSYS and its deck is modelled with shell elements. The goal of developing three numerical models is to be consistent in the comparison with the experimental results in terms of static and modal behavior. The FE models are validated by performing a static and a modal analysis. Besides, from the modal analysis it can be deduced that the first five modes of the Streicker Bridge are flexural modes including torsion in some of its members. After the first flexural modes, the following six modes are lateral or lateral/flexural for the three numerical models. Finally, a transient analysis that accounts for a running pedestrian is presented. The moving and time-varying force induced by the pedestrian is modelled according to the sinusoidal approach proposed in Sétra guidelines. The maximum vertical acceleration recorded (0.17 m/s2) is below the threshold of Comfort class CL 1 (0.50 m/s2) in accordance to HiVoSS guidelines.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/149365