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PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping
Finite Element Analysis of Walking Vibration Problems for Tubular Steel-Concrete Composite Footbridges
G.L. Debona1, J.G. Santos da Silva2, A.C.C.F. Sieira2, P.C.G. da S. Vellasco2 and L.R.O. de Lima2
1Civil Engineering Post-Graduate Programme, PGECIV, 2Structural Engineering Department,
G.L. Debona, J.G. Santos da Silva, A.C.C.F. Sieira, P.C.G. da S. Vellasco, L.R.O. de Lima, "Finite Element Analysis of Walking Vibration Problems for Tubular Steel-Concrete Composite Footbridges", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 23, 2012. doi:10.4203/ccp.99.23
Keywords: dynamic analysis, fatigue analysis, structural dynamics, tubular steel-concrete composite footbridges.
The use of circular hollow section members as part of the structure of pedestrian footbridges is a relatively new constructional concept. During the last few years several steel-concrete composite footbridges had been constructed in Brazil. The typical cross-sections of this type of pedestrian footbridge are constituted by a tubular spatial truss girder carrying the concrete deck slab .
Pedestrian footbridges are currently subjected to dynamic actions with variable magnitudes from the pedestrians crossing on the concrete deck. These dynamic actions can generate the nucleation of fractures or even their propagation in the structure. Depending on the magnitude and intensity, these adverse effects can compromise the structural system response and the reliability which may also lead to a reduction of the expected footbridge service life [1,2].
On the other hand, the structural engineers experience and knowledge allied with the use newly developed materials and technologies have produced tubular steel and composite footbridges with daring structures. This fact has generated very slender pedestrian foot-bridges and consequently changed the serviceability and ultimate limit states associated with their design. A direct consequence of this design trend is a considerable increase in structural vibration .
Considering all the aspects mentioned above, the main objective of this paper is to investigate the dynamic behaviour of tubular composite (steel-concrete) footbridges subjected to human walking vibration. The investigated structural model was based on a tubular footbridge, spanning 82.5m. The structure is composed by three spans (32.5m, 17.5m and 20.0m, respectively) and two overhangs (7.50m and 5.0m, respectively). The structural system is constituted by tubular steel sections and a concrete slab and is currently used for pedestrian crossing [1,2].
The structural system dynamic response, in terms of peak accelerations, was obtained and compared with the limiting values proposed by several authors and design standards . The peak acceleration values found in the present investigation indicated that the analysed tubular footbridge presented problems related with human comfort. Hence it was detected that this type of structure can reach high vibration levels that can compromise the footbridge user comfort and especially its safety.
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