Dynamic analyses of a curved cable-stayed footbridge under human induced vibrations: numerical models and experimental tests

Nowadays, pedestrian bridges are increasingly lively and slender structures due to the development of improved structural materials and aesthetic requirements. As a result of this trend, contemporary footbridges are more and more prone to human-induced vertical and lateral vibrations that can compromise the comfort serviceability conditions. The goal of this paper is to characterize the dynamic behaviour of a curved cable-stayed footbridge subjected to pedestrian loads starting from experimental tests and numerical dynamic analyses. The dynamic behaviour of the footbridge is investigated thanks to an experimental campaign performed by means of an advanced MEMS-based SHM system. Accelerations due to ambient vibrations are recorded and the modal parameters of the structure are identified by means of a classic identification method. Then, to investigate the dynamic response of the footbridge subjected to pedestrian actions, a wide number of experimental tests were performed with different-sized groups of pedestrians crossing the footbridge, running, free or synchronized walking with different pacing frequencies. Then, a finite element model of the footbridge is developed and calibrated so that the numerical dynamic predictions agree with the experimental modal properties. Then, to simulate dynamic loading conditions due to a single pedestrian or a crowd of people crossing the footbridge, two mathematical models are examined. In the first approach both the non-calibrated and the updated FE model are adopted to evaluate the vertical dynamic response of the footbridge when subjected to pedestrian loads. Dynamic analyses are performed by simulating the pedestrian walking through a periodic load model representing the human-induced force as a deterministic force. The second approach is based on the solution of the equation of motion via modal decomposition, considering multiharmonic forces and experimental mode shapes and frequencies. Finally, the accelerations obtained through the mathematical approaches are compared with the experimental results.

[1]  Roberto Guidorzi,et al.  Structural monitoring of a tower by means of MEMS-based sensing and enhanced autoregressive models , 2014, Eur. J. Control.

[2]  Marco Savoia,et al.  Dynamic monitoring of the Pasternak footbridge using MEMS-based sensing system , 2015 .

[3]  Paul Reynolds,et al.  Vibration serviceability of footbridges under human-induced excitation : a literature review , 2005 .

[4]  A. Hamam,et al.  Measuring and Modeling Dynamic Loads Imposed by Moving Crowds , 1996 .

[5]  C. Van Hoof,et al.  A 3-axis accelerometer and strain sensor system for building integrity monitoring , 2011, 2011 16th International Solid-State Sensors, Actuators and Microsystems Conference.

[6]  Geert Lombaert,et al.  Vibration serviceability of footbridges: Evaluation of the current codes of practice , 2014 .

[7]  Anil Kumar,et al.  Identification, Model Updating, and Validation of a Steel Twin Deck Curved Cable‐Stayed Footbridge , 2014, Comput. Aided Civ. Infrastructure Eng..

[8]  Christos T. Georgakis,et al.  Pedestrian-induced lateral vibrations of footbridges: A literature review , 2012 .

[9]  Piotr Omenzetter,et al.  A spectral density approach for modelling continuous vertical forces on pedestrian structures due to walking , 2004 .

[10]  Bernhard Sendhoff,et al.  A framework for evolutionary optimization with approximate fitness functions , 2002, IEEE Trans. Evol. Comput..

[11]  Hugo Bachmann.  " Lively" footbridges - A real challenge , 2002 .

[12]  Rune Brincker,et al.  Modal identification of output-only systems using frequency domain decomposition , 2001 .

[13]  Loris Vincenzi,et al.  A surrogate-assisted evolutionary algorithm for dynamic structural identification , 2014 .

[14]  Filipe Magalhães,et al.  Studies for controlling human-induced vibration of the Pedro e Ines footbridge, Portugal. Part 1: Assessment of dynamic behaviour , 2010 .

[15]  Quanwang Li,et al.  Crowd-induced random vibration of footbridge and vibration control using multiple tuned mass dampers , 2010 .

[16]  Gérard Grillaud,et al.  Dynamic Behaviour of a Long-Span Steel Footbridge. Characterisation and Modelling of the Dynamic Loading Induced by a Moving Crowd on the Solférino Footbridge in Paris , 2005 .

[17]  Paul Reynolds,et al.  Probability-based prediction of multi-mode vibration response to walking excitation , 2007 .

[18]  Shun-ichi Nakamura.  MODEL FOR LATERAL EXCITATION OF FOOTBRIDGES BY SYNCHRONOUS WALKING , 2004 .

[19]  Marco Savoia,et al.  Coupling Response Surface and Differential Evolution for Parameter Identification Problems , 2015, Comput. Aided Civ. Infrastructure Eng..

[20]  P Dallard,et al.  The London Millennium Footbridge , 2001 .