EXPERIMENTAL ASSESSMENT OF MULTIAXIAL LOADS INDUCED BY PEDESTRIAN GAIT ON LATERAL VIBRATING SURFACES

The introduction of increasingly resistant and lightweight materials in the construction industry, coupled with the hypothesis of a global regeneration of urban structures with higher technical and aesthetic requirements, has resulted in civil structures such as bleachers, stairs, slabs, and specifically the footbridge being vulnerable to excessive vibrations due to dynamic loads, especially gait human-induced loads. These loads present interrelation phenomena with structural vibrations, and vice versa, generated by coupling effects commonly known as Human-Structure Interaction (HSI). Two main aspects are considered in the effects of HSI: the change in dynamic properties of the structure due to the additional presence of non-stationary mass and damping, and the degree of coupling between pedestrians in transit, as well as between them and the structure. Therefore, this paper focuses on the study experimental of the last aspect, referred to as effects Structure-to-Human Interaction (S2HI), considered through the development of a Dynamic Platform, the Human-Structure Interaction Multiaxial Test Framework (HSI-MTF), to acquire the vertical and lateral loads induced by human gait under the effects of surfaces with lateral harmonic motions and on rigid surface. An experimental campaign was conducted with seven subjects of test (ST) to evaluate gait loads on rigid and harmonic lateral surfaces with displacements between 5.0 to 50.0 mm and frequency content from 0.70 to 1.30 Hz. An analysis of the support (T_su) and swing (T_sw) time of human gait was carried out with a low-cost motion capture system using smartphone devices. The periods T_su and T_sw of each ST on lateral harmonic surfaces evaluated showed differences of up to 96.53% and 58.15%, respectively, compared to the periods recorded on rigid surfaces. Subsequently, the evaluation of normalized lateral loads (LL) with respect to the weight W0 of the structural component reveals a linear growth of magnitude proportionate to the increase in lateral excitation frequency. Similarly, an augmentation in this proportionality constant has been ascertained in relation to the increment in lateral vibration amplitude, thus enabling the execution of linear regressions with an average R2 of 0.815. As for the normalized vertical load (LV) with respect to W0, a consistent behavior is observed for amplitudes up to 30.0 mm; beyond this threshold, a linear increase in magnitude is determined, directly proportional to the rise in frequency, yielding increments of 28.3% compared to those induced on a rigid surface. Lastly, the existing correlation levels between the structural components and lateral vibrations are determined utilizing the Pearson linear correlation coefficient based on optical data