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

建筑行业中高强度轻质材料的持续应用，叠加全球城市建筑结构更新（技术与美学要求均大幅提升）的发展趋势，使得看台、楼梯、楼板，尤其是人行天桥等民用建筑结构，在动态荷载尤其是行人步行荷载作用下极易产生过量振动。这类荷载与结构振动之间存在相互作用现象，反之亦然，这种耦合效应通常被称为人-结构相互作用（Human-Structure Interaction, HSI）。人-结构相互作用的效应主要包含两个方面：一是由于附加的非定常质量与阻尼导致结构动力特性发生变化；二是通行行人之间，以及行人与结构之间的耦合程度。因此，本文聚焦于上述第二个方面的试验研究，该方面被称为结构-人相互作用效应（Structure-to-Human Interaction, S2HI）。研究通过搭建动态试验平台——人-结构相互作用多轴测试框架（Human-Structure Interaction Multiaxial Test Framework, HSI-MTF），以获取行人在侧向简谐运动台面以及刚性台面上步行时产生的竖向与侧向荷载。本试验招募7名试验受试者（Test Subject, ST）开展试验，以测试其在位移幅值5.0~50.0 mm、频率范围0.70~1.30 Hz的侧向简谐运动台面以及刚性台面上的步行荷载。研究采用基于智能手机的低成本运动捕捉系统，对行人步行的支撑相时间（T_su）与摆动相时间（T_sw）进行分析。试验结果显示，与刚性台面上测得的步行相时程相比，侧向简谐运动台面上各受试者的支撑相时间与摆动相时间最大偏差分别可达96.53%与58.15%。随后，以结构自重W0为基准的归一化侧向荷载（LL）分析结果表明，荷载幅值随侧向激励频率的提升呈线性增长趋势。同理，该比例常数随侧向振动幅值的增大而提升，据此开展的线性回归分析平均决定系数（R²）可达0.815。针对以W0为基准的归一化竖向荷载（LV），当侧向振动幅值不超过30.0 mm时，其变化规律保持一致；当幅值超过该阈值后，荷载幅值随频率提升呈线性增长，相较于刚性台面上的步行荷载最大增幅可达28.3%。最后，研究基于光学捕捉数据，采用皮尔逊线性相关系数，量化分析了结构构件与侧向振动之间的相关程度。