Análise de vibrações de passarelas de pedestres submetidas a cargas dinâmicas de vandalismo

Abstract

This research work aims to investigate the dynamic structural behaviour of pedestrian footbridges, when subjected to dynamic actions associated to vandalism, based on the development of experimental tests and numerical modelling. Therefore, three traditional mathematical models used to characterize the human actions are investigated using the Hanning, semi-sinusoidal and triangular functions. The experimental tests are carried out on an existing concrete footbridge, located at the Faculty of Engineering (FEN) of the State University of Rio de Janeiro (UERJ). The structural system is simply supported spanning 24.4 m, currently used for pedestrian crossing. Initially, the modal analysis of the structure was conducted based on experimental tests, aiming to characterize the natural frequencies and vibration modes. Then, different loading situations were considered to carry out experimental forced vibration tests on the footbridge, with the participation of up to 20 people, aiming to simulate dynamic excitations of vandalism. The footbridge numerical modelling was developed based on the use of the ANSYS finite element program, and the numerical model was used to calibrate the results obtained based on the structure experimental monitoring. After that, the studied footbridge dynamic structural response was numerically assessed and the human comfort levels were compared with criteria established in standards and design recommendations. Analysing the research results, it is highlighted that when 20 people produce rhythmic dynamic actions on the structure, the peak acceleration value is about of 1.50 m/s2 (ap = 1.50 m/s2), corresponding to a minimum comfort level.