Análisis de la interacción humano-estructura en el diseño de puentes peatonales modulares con sección trapezoidal en acero plegado en frío

Abstract

the last century, as society has advanced at an accelerated pace, structural systems have evolved in response to societal needs. Among these structures, numerous civil engineering works—such as stairways, footbridges, grandstands, and pedestrian bridges—have exhibited problems related to excessive vibrations. These structures often present high flexibility and low damping, which significantly increases their susceptibility to vibration-related issues, particularly due to the phenomenon known as human–structure interaction. This phenomenon originates from the coupling of two subsystems: human locomotion and the structural response of the bridge to dynamic excitation. Resonance may occur when the natural frequency of the structure coincides with or approaches the frequency associated with human walking. Although most pedestrian bridges are designed in accordance with current design codes, considerable uncertainty remains regarding their behavior under dynamic loads induced by pedestrians. Such loads may lead to undesirable responses, potentially resulting in structural deficiencies or serviceability failures due to excessive vibrations. This study focuses on the analysis of pedestrian bridges with composite sections, consisting of a cold-formed trapezoidal steel girder and a prefabricated reinforced concrete deck slab. A numerically coupled pedestrian–bridge model was developed using Octave, in which the pedestrian is represented as a biodynamic subsystem and the bridge structure is modeled as a finite element subsystem. This approach allows for the explicit evaluation of the bidirectional interaction between both subsystems. Three different bridge cross-sections and two typical span lengths (13 m and 20 m) were analyzed. The corresponding natural frequencies and maximum accelerations induced by a representative pedestrian were evaluated. The results demonstrate that the fundamental natural frequency of the bridge is the dominant parameter governing its vibratory response. Furthermore, it was determined that structures with natural frequencies below 3.5 Hz exhibit high acceleration levels that exceed the comfort limits established by international design codes such as AASHTO LRFD, leading to unacceptable serviceability conditions. IV Conversely, bridge sections with higher natural frequencies exhibit stable dynamic responses, characterized by acceleration levels that are imperceptible to pedestrians. This graduation project investigates the phenomenon of human–structure interaction in modular pedestrian bridges, considering its direct influence on dynamic behavior, user comfort, and structural performance. The primary objective is to quantify maximum acceleration levels and assess the comfort performance of each bridge configuration, particularly in light of the fact that current design codes do not mandate dynamic serviceability analyses for pedestrian bridges nor establish explicit control parameters to prevent failures associated with human–structure interaction. Keywords: Resonance, vibration, subsystem, comfort, coupling