STRIDE - Our flagship project

Walking is a seemingly simple everyday activity serving to move the body in space. This is achieved by pushing feet against the ground hence generating ground reaction forces. The nature of these forces is well understood – we are pushing up against the ground to support the body against the action of gravity, we are pushing back to propel the body forward, and we are pushing sideways to enable bipedal gait and ensure that balance is maintained. Nevertheless, modelling pedestrian ground reaction forces remains a challenge in the structural engineering community.

Project outline

A formidable challenge is posed for the designers of civil engineering structures by the uncertainty in pedestrian behaviour. This challenge arises since pedestrians have capacity to interact with vibrating structures and each other, which can lead to a rapid growth of dynamic structural response amplitudes, i.e. structural instability. Structural instability, which is increasingly common in modern light and slender structures, can render structures unfit for their purpose and requiring costly retrofitting solutions. In some cases, it can even create a risk to human life.

As evidenced by the many cases of structural instability reported all over the world, there is little confidence in that the current guidelines for the design of structures against pedestrian-induced loading can be trusted. This derives from the very origin of data used in their calibration. These data come from either pedestrian-loading tests on full scale structures or laboratory experiments. In the former case, the structural response is typically measured while the behaviour of pedestrians has to be assumed to fit that response. This top-down approach leads to the bias towards higher organisational rank – here the behaviour of the structure, and can obstruct rather than facilitate the understanding of the coupled system dynamics. In the latter case, a single pedestrian is typically tested in an artificial environment. This bottom-up approach disallows ecological complexity of real-world settings to be captured and ignores the fact that structures are usually occupied by many pedestrians at the time.

A new approach to investigating the effects of crowds on structures is required, enabling simultaneous measurement of pedestrians’ forces and structural response in situ. The collected data can be then analysed to understand the significance of pedestrian-structure and pedestrian-pedestrian interaction mechanisms, and to conceive a fundamental pedestrian loading model. This in turn can enable a reliable set of structural design guidelines to be defined – a task which is now long overdue.

The funding for the project was awarded to Dr Mateusz Bocian by the Polish National Agency for Academic Exchange (NAWA) via Polish Returns programme.