Human-Structure Interaction Dynamics in Footbridge Vibration Serviceability

Footbridge vibration serviceability hinges on the dynamic interplay between pedestrian-induced forces and the structural response of low-frequency, lightly damped spans. When people walk, their vertical and lateral footfalls excite the bridge deck at frequencies often close to the natural modes of the structure. This coupling alters the system’s effective mass, stiffness and damping and may give rise to uncomfortable or unsafe levels of vibration. Understanding these human-structure interaction (HSI) dynamics requires simultaneous consideration of gait variability, group synchronisation effects and the spatial distribution of moving loads. Advanced experimental campaigns, numerical simulations and refined analytical models have revealed that pedestrians not only impose forces but also modulate structural properties in situ, often increasing apparent damping but occasionally triggering resonance. Modern serviceability assessment has therefore evolved beyond static peak-force checks towards probabilistic models and full human-in-the-loop frameworks, aiming to predict acceleration levels experienced by individuals across a range of walking speeds, group sizes and bridge typologies. The global significance of these developments spans from iconic long-span footbridges in urban centres to lightweight composite crossings in remote regions, where comfort criteria and design codes must keep pace with emerging HSI insights.

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Recent literature has advanced three complementary areas of HSI dynamics. A comprehensive review of vertical human-structure interaction mechanisms has synthesised decades of experimental and analytical work, highlighting key knowledge gaps in modelling multi-pedestrian loading and the need for coherent codification of walking variability. Experimental comparisons of fibre-reinforced polymer footbridges against conventional steel and concrete structures have quantified modal masses, natural frequencies and damping ratios, revealing that composite decks exhibit similar frequencies but higher damping and greater acceleration under resonant excitation. Finally, a novel single-sensor calibration method for spring-mass-damper pedestrian models has demonstrated the potential of using a single centre-of-mass accelerometer to derive personalised mass, stiffness and damping parameters, validated through extensive gait trials and parametric dynamic analyses. Together, these studies reinforce the importance of probabilistic, occupant-centred design frameworks and provide concrete data for updating serviceability guidelines on a global scale.

Human-Structure Interaction Dynamics in Footbridge Vibration Serviceability publication trend

The graph below shows the total number of articles in human-structure interaction dynamics in footbridge vibration serviceability across all publications each year (not limited to Nature Index journals).

Technical terms

Human-Structure Interaction (HSI): The bidirectional dynamic coupling between moving pedestrians and a structure, whereby each influences the motion and forces of the other.

Vibration Serviceability: The criterion defining acceptable levels of structural vibration, typically in terms of peak accelerations, to ensure occupant comfort and functionality.

Natural Frequency: The frequency at which a structure or system oscillates when disturbed and then left to vibrate freely, determined by its mass and stiffness distribution.

Damping Ratio: A dimensionless parameter describing the rate at which vibrating energy is dissipated, influenced by material properties and human-induced energy absorption.

Modal Mass: The effective mass participating in a particular vibration mode, affecting amplitude under dynamic loading.

Spring-Mass-Damper (SMD) Model: A reduced-order representation of a pedestrian’s mechanical behaviour, characterised by equivalent mass, spring stiffness and viscous damping coefficients.

References

1. Single body sensor for calibration of Spring-Mass-Damper parameters in biodynamic pedestrian modelling. Measurement (2023).
2. Interaction between Walking Humans and Structures in Vertical Direction: A Literature Review. Shock and Vibration (2016).
3. Measured dynamic properties for FRP footbridges and their critical comparison against structures made of conventional construction materials. Composite Structures (2019).
4. Structural vibration serviceability: New design framework featuring human-structure interaction. Engineering Structures (2017).