1,721,026 research outputs found
Applying walking and running forces
No full textVitomir Racic, who was awarded with the second prize in the poster category of the 2009 Young Researchers' Conference, reports on his research into the application of human walking and running forces in civil engineering dynamics. A key advance in the proposed approach is utilization of free-field measurements of continuous walking/running forces without artificial constraints imposed by the direct measurement system. The approach has made possible study of areas of significant interest and uncertainty, specifically human-structure dynamic interaction and pedestrian coordination when walking on more or less perceptibly moving structures in real-life environments, such as office floors and footbridges. A series of walking tests, which involved simultaneous recording of body and structure motion, was carried out on the 'EMPA Intelligent Cable Stayed Bridge' in July 2009. The results are expected to assist novel development of numerical force time series generators replicating real walking under different conditions leading to more rational and efficient designs
Emerging research on vibration serviceability of footbridges due to pedestrian crowds
No full textDespite a growing number of reported vibration serviceability
problems worldwide of newly build footbridges due to pedestrians
walking, there is still a lack of adequate codes of practice.
There are three key issues that a new generation of the relevant
design guidelines should urgently address: effect of human
bodies on dynamic properties of a structure, inter-subject and
intra-subject variability of pedestrian dynamic excitation and
pedestrian “intelligent” interaction with the surrounding people
and environment. This article provides a brief overview of the
relevant state-of-the-art research that has a great potential to
change this unsatisfactory state of affairs
Stochastic model of near-periodic jumping forces
No full textA mathematical model has been developed to generate stochastic synthetic vertical force signals induced by a single person jumping. The model is based on a unique database of experimentally measured individual jumping loads which has the most extensive range of possible jumping frequencies. The ability to replicate many of the temporal and spectral features of real jumping loads gives this model a definite advantage over the conventional half-sine models coupled with Fourier series analysis. This includes modelling of the omnipresent lack of symmetry of individual jumping pulses and jump-by-jump variations in amplitudes and timing. The model therefore belongs to a new generation of synthetic narrow band jumping loads which simulate reality better. The proposed mathematical concept for characterisation of near-periodic jumping pulses may be utilised in vibration serviceability assessment of civil engineering assembly structures, such as grandstands, spectator galleries, footbridges and concert or gym floors, to estimate more realistically dynamic structural response due to people jumping
Mathematical model to generate asymmetric pulses due to human jumping
No full textA novel mathematical modeling has been proposed to generate synthetic vertical force signal induced by a single person jumping. This model can replicate much of the temporal and spectral features of the real jumping loading more reliably than the existing half-sine models coupled with Fourier series analysis. This includes lack of symmetry of individual jumping pulses and near-periodic nature of consecutive pulses. The model therefore offers way forward as to the development of a new generation of synthetic narrow-band jumping loads. In these, the shape and frequency content of the jumping force can be changed easily on a jump-by-jump basis, which simulates better on what is happening in reality during human jumping. The synthetic jumping loading can be used in assessing vibration serviceability of civil engineering structures for which such dynamic excitation is relevant, such as assembly structures and concert venues
Mathematical model to generate near-periodic human jumping force signals
No full textA mathematical modelling procedure has been developed to generate synthetic vertical force signals induced by a single person jumping. The ability to replicate much of the temporal and spectral features of real jumping loads give this model a definite advantage over the conventional half-sine models coupled with Fourier series analysis. This includes modelling of the omnipresent lack of symmetry of individual jumping pulses and jump-by-jump variations in amplitudes and timing. The model therefore belongs to a new generation of synthetic narrowband jumping loads that simulate reality better. The proposed mathematical concept for characterisation of irregular jumping pulses may be utilised in vibration serviceability assessment of civil engineering assembly structures, such as grandstands, footbridges and concert or gym floors, to estimate realistic dynamic structural response due to people jumping. (C) 2009 Elsevier Ltd. All rights reserved
Footfall model for design of high frequency floors
No full textDynamic loading due to people walking is one of the most relevant dynamic excitations for design of floors housing vibration sensitive facilities. Such floors are commonly designed as "high frequency floors" showing a transient response due to successive footfalls. According to the contemporary UK design guideline, their fundamental frequency should be higher than 10 Hz to avoid the resonance. Contrary to the popular belief, this study shows that the resonance can still develop when the natural frequency is in the range 10-20 Hz. Motivated by the existing model of footfall forces featuring the current UK Concrete Society guideline for design of floors, a new mathematical model has been developed to evaluate more reliably vibration serviceability of high frequency floors
Data-driven generator of stochastic dynamic loading due to people bouncing
Full text linkThe latest design guideline relevant to bouncing loads describes bouncing as deterministic and periodic process presentable via Fourier series. However, fitting the Fourier harmonics to a comprehensive database of individual bouncing force records established in this study showed that such a radical simplification of the reality leads to a significant loss of key information. Hence, this study brings the Fourier model to a higher level, where the fitted harmonics are personalised, randomised and the natural variability taken into account, leading to a stochastic generator of near-periodic bouncing force time histories which can simulate reliably the actual measurements
Data-driven modelling of vertical dynamic excitation of bridges induced by people running
Full text linkWith increasingly popular marathon events in urban environments, structural designers face a great deal of uncertainty when assessing dynamic performance of bridges occupied and dynamically excited by people running. While the dynamic loads induced by pedestrians walking have been intensively studied since the infamous lateral sway of the London Millennium Bridge in 2000, reliable and practical descriptions of running excitation are still very rare and limited. This interdisciplinary study has addressed the issue by bringing together a database of individual running force signals recorded by two state-of-the-art instrumented treadmills and two attempts to mathematically describe the measurements. The first modelling strategy is adopted from the available design guidelines for human walking excitation of structures, featuring perfectly periodic and deterministic characterisation of pedestrian forces presentable via Fourier series. This modelling approach proved to be inadequate for running loads due to the inherent near-periodic nature of the measured signals, a great inter-personal randomness of the dominant Fourier amplitudes and the lack of strong correlation between the amplitudes and running footfall rate. Hence, utilising the database established and motivated by the existing models of wind and earthquake loading, speech recognition techniques and a method of replicating electrocardiogram signals, this paper finally presents a numerical generator of random near-periodic running force signals which can reliably simulate the measurements. Such a model is an essential prerequisite for future quality models of dynamic loading induced by individuals, groups and crowds running under a wide range of conditions, such as perceptibly vibrating bridges and different combinations of visual, auditory and tactile cues
Mathematical modelling of near-periodic jumping force signals
No full textA mathematical modelling procedure has been developed to generate synthetic vertical force signals induced by a single person jumping. The ability to replicate much of the temporal and spectral features of real jumping loads gives this model a definite advantage over the conventional half-sine models coupled with Fourier series analysis. This includes modelling of the omnipresent lack of symmetry of individual jumping pulses and beat-by-beat variations in amplitudes and timing. The model therefore belongs to a new generation of synthetic narrow-band jumping loads which simulate reality better. The proposed mathematical concept for characterisation of irregular jumping pulses may be utilised in vibration serviceability assessment of civil engineering assembly structures, such as grandstands, spectator galleries and gym floors, to estimate realistic dynamic structural response due to people jumping. ©2010 Society for Experimental Mechanics Inc
Novel experimental characterisation of human-induced loading
No full textState-of-the-art facilities for measuring human-induced dynamic forces comprise typically equipment for direct force measurement, made of a single or several force plates and an instrumented treadmill mounted on a rigid laboratory floor. Artificial laboratory conditions and constraints imposed by the direct measurement systems, such as small measuring area of a force plate and constant speed of rotation of a treadmill belt, can exert a strong influence on human ability to move naturally, and hence may alter corresponding ground reaction forces. However, when dealing with issues like vibration serviceability of real full-scale structures such as grandstands, floors and footbridges, there is a growing need to estimate loads applied directly by occupants under a wider range of conditions in outdoor environments. This paper thus presents a novel method to utilise 'free field' measurement of human-induced excitation continuously in time using motion capturing technology. Such data are crucial for establishing a new generation of mathematical models of dynamic forces generated by individuals and groups of people when bouncing, jumping, walking, etc. © 2009 Society for Experimental Mechanics Inc
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