Validation of mass-spring-damper models for human-structure interaction on an ultra-lightweight footbridge

The vibration serviceability assessment (VSA) of footbridges necessitates a conservative yet reliable estimation of human-induced vibrations. Existing design guidelines typically model pedestrian loads as forces exerted by crowds on a rigid surface, thereby overlooking the dynamic interaction between the human body and the structure, commonly referred to as Human-Structure Interaction (HSI). This simplification tends to overestimate structural responses, resulting in overly conservative designs. To account for HSI effects, the mechanical system of the human body, often represented by a Single Degree Of Freedom (SDOF) system, must be accurately characterized. Although various estimates of human body parameters exist in literature, research involving ultra-lightweight structures, such as short span Fiber-Reinforced Polymer (FRP) footbridges subjected to realistic crowd scenarios, remains limited. This study investigates the applicability of SDOF parameters available in literature for an all-FRP lightweight structure based on a full-scale, in-situ measurement of a walking crowd consisting of 31 participants. It is found that, for this specific event, the SDOF representation in literature and its accompanying parameter values are well suited to simulate HSI.