Facta universitatis - series: Architecture and Civil Engineering 2002 Volume 2, Issue 4, Pages: 281-289
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Some relevant aspects of footbridge vibrations

Spasojević Ana, Đorđević Đorđe, Spasojević Marija, Spasojević Novak

Considering the contemporary structural inaterials that are becoming more resistant, having higher strength to weight ratio, and the fact that live load of footbridges is low, the design based on static analysis only, respecting ultimate limit states requirements, leads to slender bridge structures for pedestrian and cycle track use. As a consequence, stiffness and masses decrease, facing lively, easy to excite structures, with smaller natural frequencies. The excitation of a footbridge by a pedestrian passing over it can be unpleasant for a person walking or standing on the bridge, but usually not destructive for the structure itself. Recent experiences regarding dynamic behavior of slender footbridges have especially shown that vibration serviceability limit states are very important requirements in any structural design. We are presenting a general algorithm for analytical testing of dynamic parameters of structures, calculation of deflection, thus speed and acceleration of superstructure under human-induced excitation, as predicted by Eurocode, British and Canadian standards in use, since no Yugoslav code deals with the problem. The evaluated system is a footbridge in a system of a simply supported concrete girder. The presented model is used to show correspondence of results, obtained by the algorithm, with the results obtained using the simplified methods suggested by the Codes of Practice, since the latter exists only for certain structural systems.

Keywords: footbridge, human-induced excitation, forced vibrations, serviceability limit states

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