A spectral density approach for modelling continuous vertical forces on pedestrian structures due to walking

Peer reviewedPreprin

Analysis of Load Test on Composite I-Girder Bridge

Proceedings of the CSHM-6: Structural Health Monitoring of New and Ageing Infrastructure, Queen's University Belfast, Northern Ireland, United Kingdom, 26-27 May 2016This paper showcases the importance of field testing in efforts to deal with the deteriorating infrastructure. It demonstrates a load test performed on a healthy but aging composite reinforced concrete bridges in Exeter, UK. The bridge girders were instrumented with strain transducers and static strains were recorded while a four-axle, 32 tonne lorry remained stationary in a single lane. The results obtained from the field test were used to calculate transverse load distribution factors (DFs) of the deck structure for each loading case. Additionally, a 3-D finite element model of the bridge was developed and calibrated based on field test data. Similar loading cases were simulated on the analytical model and behaviour of the structure under static loading was studied. It was concluded that the bridge support conditions had changed throughout its service life, which affected the superstructure load distribution characteristics. Finally, DFs obtained from analysis were compared with factors provided in Design Manual for Roads and Bridges Standard Specification for similar type of bridges.European Union’s Horizon 2020Marie Skłodowska–Curie gran

Analysis of the shearing instability in nonlinear convection and magnetoconvection

Numerical experiments on two-dimensional convection with or without a vertical magnetic field reveal a bewildering variety of periodic and aperiodic oscillations. Steady rolls can develop a shearing instability, in which rolls turning over in one direction grow at the expense of rolls turning over in the other, resulting in a net shear across the layer. As the temperature difference across the fluid is increased, two-dimensional pulsating waves occur, in which the direction of shear alternates. We analyse the nonlinear dynamics of this behaviour by first constructing appropriate low-order sets of ordinary differential equations, which show the same behaviour, and then analysing the global bifurcations that lead to these oscillations by constructing one-dimensional return maps. We compare the behaviour of the partial differential equations, the models and the maps in systematic two-parameter studies of both the magnetic and the non-magnetic cases, emphasising how the symmetries of periodic solutions change as a result of global bifurcations. Much of the interesting behaviour is associated with a discontinuous change in the leading direction of a fixed point at a global bifurcation; this change occurs when the magnetic field is introduced

Mathematical modelling of random narrow band lateral excitation of footbridges due to pedestrians walking

Motivated by the existing models of wind and earthquake loading, speech recognition techniques and a method of replicating electrocardiogram (ECG) signals, this paper presents a mathematical model to generate synthetic narrow band lateral force signals due to individuals walking. The model is fitted to a database comprising many directly measured walking time series, yielding a random approach to generating their artificial - yet realistic counterparts. This multi-disciplinary modelling strategy offers a radical departure from traditional Fourier-based representations of lateral walking loads towards more reliable and more realistic vibration serviceability assessment of footbridges

Stochastic model of continuously measured vertical pedestrian loads

Stochastic and narrow band nature are the two essential features of vertical walking loading not addressed adequately in the existing design guidelines for pedestrian structures, such as footbridges, long-span floors and staircases. One of the reasons for this is the lack of a comprehensive database of walking forces in the form of continuously recorded time series that can be used for development of statistically reliable characterisation of these forces for application in the civil engineering context. This paper has addressed the issue by establishing a large database of measured walking time series recorded by a state-of-the-art in-stru-mented treadmill at the University of Sheffield. Another reason is the lack of an adequate modelling strategy which can simulate reliably the actual forcing signals. Here, a data-driven mathematical model has been developed to generate synthetic force signals with realistic temporal and spectral features. The modelling strategy takes a complex numerical approach, thus can be coded as a user-friendly soft-ware which can be adopted in the vibration serviceability design practice

Reproduction and application of pedestrian forces from visual marker data

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