Numerical and experimental assessment of the dynamic behavior of a pedestrian bridge

As the years go by, engineers face the challenge of designing and constructing more and more slender and lightweight structures, including pedestrian bridges. Consequently, structural engineers must deal with much more flexible and sensitive structures with respect to the action of dynamic loadings. Slender lightweight pedestrian bridges are characterized by natural frequency values that are close to the frequencies characterizing pedestrian dynamic loading. In this sense, the risk for this type of structures of experimenting resonance phenomena increases. The large acceleration values experimented during resonance may cause a feeling of discomfort for the users of the pedestrian bridges. For this reason, the dynamic behavior of pedestrian bridges must be assessed during the design phase to guarantee the serviceability of the structure. In this work, an existing pedestrian bridge, located at the municipality of Cerro al Lambro, Italy, was analyzed. First of all, finite element models (FEM) were developed in SAP2000 with the aim of reproducing the natural mode shapes and frequencies characterizing the actual dynamic behavior of the structure, which was previously studied through Ambient Vibration Tests (AVT). Followed by this, once an accurate finite element model was obtained, the maximum level of comfort that the pedestrian bridge may provide for diverse pedestrian traffic situations was assessed employing the methodology proposed in the HiVoSS Design of Footbridges Guidelines. Finally, acceleration records obtained from an experimental campaign carried out on the pedestrian bridge were analyzed. For this experimental campaign, different groups of pedestrian induced vibrations on the footbridge by walking synchronously with a step frequency equal to the natural frequency of vibration of the first flexural-vertical mode for the structure.

Da definire.