Pedestrian-Induced Vibrations of Footbridges: An Extended Spectral Approach

Nimmen, Katrien Van; Broeck, Peter Van den; Lombaert, Geert; Tubino, Federica

doi:10.1061/(asce)be.1943-5592.0001582

Cited by 14 publications

(4 citation statements)

References 58 publications

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“…Traditionally the peak value of the integer harmonic is taken as the selected DLF for each harmonic of the walking frequency. Such a constrained methodology negates any information the surrounding narrow-band signal produces [27,28,55]. Whilst the DLF of the peak value provides the majority energy of each harmonic, the surround energy acts to either increase or decrease the relative magnitude of the time signal through slight off frequency forcing functions.…”

Section: Extraction Of Dlfs and Walking Frequenciesmentioning

confidence: 99%

“…Contemporary guidance commonly perceives walking forces as a deterministic process. However, recent research demonstrates that walking is far more accurately described as a narrow band stochastic process [27][28][29]. The vertical walking force proposed in design guidance is determined via the natural frequency of the structure in question.…”

Section: Introductionmentioning

confidence: 99%

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Fourier Series Approximation of Vertical Walking Force-Time History through Frequentist and Bayesian Inference

et al. 2022

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The increased ambition of architects coupled with advancements in structural materials, as well as the rapidly increasing pressure on civil engineering sector to reduce embodied carbon, have resulted in longer spans and more slender pedestrian structures. These structures often have one or more low natural frequencies in the range of human walking accompanied with low modal masses and damping ratios. Thus, they are prone to excessive and often resonant vibrations that may compromise the serviceability limit state. Principally the uncertainty in prediction of the vibration serviceability limit state mainly originates from unreliable estimates of pedestrian loading. The key rationale behind this situation is the limited mathematical characterisation featuring in current design codes and guidelines pertinent to pedestrian-induced loading. The Fourier approximation is typically used to describe individual walking forces. Historically, such models are based on limited experimental data and deterministic mathematical descriptions. Current industry used load models featured in design codes and guidelines have been shown to incorporate inherent bias through limited intra-subject variation and poor correlation with real walking loads. This paper presents an improved Fourier model of vertical walking force across multiple harmonics, presented in a Bayesian and Frequentist statistical parameterisation. They are derived using the most comprehensive dataset to date, comprising of over ten hours of continuous vertical walking force signals. Dissimilar to previous Fourier models, the proposed models attempt to encapsulate the surround energy leakage around harmonic integers with a singular value. The proposed models provide consistently lower force amplitudes than any previous model and is shown to be more representative of real walking. The proposed model provides a closer approximation of a structural acceleration than any other similar Fourier-based model. The proposed model provides further evidence to combine the so called high and low frequency load models.

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Section: Extraction Of Dlfs and Walking Frequenciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fourier Series Approximation of Vertical Walking Force-Time History through Frequentist and Bayesian Inference

et al. 2022

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“…Apart from the progress in material technology, a factor which makes it possible to meet engineering challenges is the development of computer software, which solves complex design problems. A consequence of the mentioned factors is the greater sensitivity of modern structures to dynamic loads [1][2][3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Vibration Serviceability of Footbridges Made of the Sustainable and Eco Structural Material: Glued-Laminated Wood

Hawryszków

Biliszczuk

2022

Materials

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In this paper, dynamic analyses of two untypical, modern footbridges made of glued-laminated timber are presented. One of them is among the longest cable-stayed bridges for pedestrians in the world, made of such a structural material. Both structures are qualified as having low sensitivity to vibrations. The results of numerical modal analysis using FEM and non-destructive experimental dynamic tests of investigated footbridges are compared. Important differences in obtained results are captured, which are identified as the positive effect in relation to design aspects. Moreover, the same in situ measurements confirm the high level of damping in footbridges made of glued-laminated wood, which is a very significant and distinguishing feature not commonly recognized. The study also calls attention to the choice of timber as an advisable material for footbridges. This is not only because of environmentally friendly and aesthetic reasons, but also due to providing highly satisfying vibration comfort for pedestrians.

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“…The present authors have recently developed a model that accounts for first five harmonics and subharmonics and is the only model that accounts for variations in speed of pedestrian crossing the bridge (García-Diéguez et al 2021). Some of the recent models have been formulated in either a spectral load or a response spectrum format that is convenient for use in design (Wan et al 2009;Brownjohn and Racic 2016;Wang et al 2020;Van Nimmen et al 2020). However, none of the proposals have yet been adopted by design guidelines for footbridges (Ricciardelli and Demartino 2015) owing to a lack of evidence of their comparative performance on as-built structures.…”

Section: Introductionmentioning

confidence: 99%

Vertical Vibration Response of Footbridges with Fundamental Natural Frequency up to 10 Hz under Dynamic Loading by Single Pedestrian

2021

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A design spectrum of characteristic acceleration response to pedestrian-induced dynamic loading has been developed for footbridge structures. The novelty of the proposed spectrum over the existing spectra is that: (1) it is underpinned by a recently developed comprehensive statistical model of pedestrian dynamic loading; (2) it is applicable to a broader natural frequency range of structures up to 10 Hz; and (3) it accounts for uncertainties in both dynamic loading and structure dynamics that are typically encountered in structural design. In addition, the importance of correct modeling of pedestrian's walking speed and narrow-band nature of the force signal has been demonstrated. Comparison with the design spectra recommended in contemporary design codes reveals that the existing approaches are not being applicable for structures with natural frequency in the range of third, fourth, and fifth harmonic of the dynamic force. In addition, they could both underestimate and overestimate the structural response for lower-frequency structures. The proposed design spectrum is a design tool applicable to structures whose mode shape can be approximated by half-sine, span length between 12.5 and 100 m, and damping ratio between 0.25% and 2%.

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Pedestrian-Induced Vibrations of Footbridges: An Extended Spectral Approach

Cited by 14 publications

References 58 publications

Fourier Series Approximation of Vertical Walking Force-Time History through Frequentist and Bayesian Inference

Fourier Series Approximation of Vertical Walking Force-Time History through Frequentist and Bayesian Inference

Vibration Serviceability of Footbridges Made of the Sustainable and Eco Structural Material: Glued-Laminated Wood

Vertical Vibration Response of Footbridges with Fundamental Natural Frequency up to 10 Hz under Dynamic Loading by Single Pedestrian

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