Investigation of The Effect of Human-Induced Vibrations on Pedestrian Cable Bridges (A Case Study of Selected Pedestrian Cable Bridge)
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Date
2019-04
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Addis Ababa University
Abstract
Many rural communities around the world become isolated from their basic needs during the rainy season. So, low cost pedestrian cable bridges are being built to provide hundreds of thousands of people with basic access. However, cable pedestrian bridges have low stiffness, mass and damping, causing them to be prone to vibration problems. Pedestrian loading can cause a dynamic effect that creates public alarm to the point where bridge users perceive it to be unsafe. Many footbridges have natural frequencies that coincide with the dominant frequencies of the pedestrian-induced load. Therefore, they have a potential to suffer excessive vibrations under dynamic loads induced by pedestrians.
The main focus of this thesis is an investigation of the effect of human-induced vibrations on pedestrian cable bridges and how the vertical forces that pedestrians impart to cable suspended footbridge can be modeled to be used in the dynamic design of footbridges. The work was mainly divided into four subtasks. First literature studies on effect of Human-Induced Vibrations on suspended footbridge have been performed. Second design criteria and load models proposed by three widely used standards have been introduced, then, numerical models using finite element software has been performed in persons walking and jogging condition to determine how changing certain design parameters including walkway and handrail cables diameter and percentage of sag and number of walking and jogging pedestrian affects modal frequencies and vertical dynamic response. Finally, the research results have been presented and discussed.
The study result showed that in most cases the modal frequencies of pedestrian suspended bridges do not meet the recommended ranges. Also, it reveals that the vertical accelerations of the structure depend on the number of walking and jogging pedestrians across the bridge. In addition, shorter bridge span length has higher modal frequencies and dynamic responses.
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human-induced, pedestrian cable bridges