Comprehensive experimental analysis of the vibration serviceability due to dynamic interaction between footbridge with accurate multi-axial dynamic sensitivity and human-induced gait loads

Description

Recent advances in structural engineering have facilitated the construction of large-scale structures by using lightweight and high-strength materials. However, despite innovative design techniques, urban footbridges are susceptible to excessive vibrations induced by human activity. Although vandalism human loads have the greatest dynamic impact on the response of footbridges, owing to their intensity and wide frequency range of affectation, human-induced gait loads have the highest recurrence, randomness, and capacity to limit the serviceability of this type of structure. Traditionally, the effects of the human-structure interaction (HSI) on large-scale footbridges have been evaluated for the structural direction that is most prone to present a dynamic sensitivity or dynamic coupling with pedestrian-induced loads. Nevertheless, these uni-axial analyses on urban large-scale footbridges do not consider the multi-directional effects of the HSI or are limited by the dynamics of the structure itself, which generates the need for experimental information and evaluation of these structures. In this study, an extensive and compressive investigation on the experimental assessment of HSI effects in a functional urban footbridge with accurate multiaxial dynamic sensitivity in relation to the typical frequency range of human-induced gait loads was performed. Initially, the reference structure was described and identified using an operational modal analysis (OMA) with structural outputs based on ambient vibrations. Subsequently, a comprehensive and detailed experimental human gait campaign was conducted for various load densities and gait conditions. The results demonstrate that multi-axial HSI effects were concentrated on the lateral fundamental frequency of the reference footbridge, there was an increase of the damping ratios in relation to the load density level of the structure with the greatest effect when the human gait is synchronous, changes in the behavior of human-induced gait loads with HSI effects compared to the rigid surface, the reference structure has serviceability limitations even for load densities considered as moderate, and has the potential to be used as an international benchmark.

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