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Investigations of orthotropic decks
Urushadze, Shota ; Frýba, Ladislav ; Pirner, Miroš
The investgations of orthotropic decks carried out in the Institute of Theoretivcal and Applied Mechanics,v.v.i., Academy of Sciensces of the Czech Republic, for the project of the European Union „BRIFAG“ are described. The response of orthotropic decks is studie under dynamic loads including the crack propagation, estimation of fatigue life of the bridge elements, e.t.c. It was found that the most vulenrable detail appeared at the spatial connection of the deck with cross and longitudinal beams. The most important results are shown in a a figure of stress ranges as a function of the number of stress cycles.
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Brifag - the EU project on the bridge fatigue
Frýba, Ladislav
The main objective of the project is to study the whole -fatigue life- of the test girder, from the initiation of the first fatigue crack to the complete fatigue failure of the whole girder. In so doing, the growth of all fatigue cracks generated in the breathing web is measured and their impact on the girder collapse mechanism studied. Some characteristic results are presented.
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Dynamic Interactions of a Train Moving Over a Rail Suspension Bridge with Multiple Support Settlements
Yau, Y. D. ; Frýba, Ladislav
With the consideration of multiple support settlements, interaction responses of a train running over a rail suspension bridge will be investigated. The suspension bridge is modeled as a single-span suspended beam with hinged ends and the train as successive moving oscillators with identical properties. To conduct this dynamic problem with non-homogeneous boundary conditions, the total deflection response of the suspended beam is divided into two parts: the static component and the dynamic deflection. Then, the coupled equations of motion for the suspended beam carrying multiple moving oscillators are converted into a set of nonlinearly coupled generalized equations by Galerkin’s method, and solved using the Newmark method using incremental-iterative procedure. From the present numerical demonstrations, the differential movements of bridge supports will significantly affect the dynamic response of the running vehicles but insignificant influence on the bridge response.
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Dynamické chování nosníku s přdpjatou strunou - vliv útlumu
Fischer, Cyril ; Frýba, Ladislav
The beam with an axial force is coupled by an elastic layer of Winkler type with the pretensiled string. It is subjected to a row of moving forces. The theoretical model corresponds to a prestressed bridge. The concrete bridges of this type are the most spread types appearing on both the road and railway bridges of small and medium spans. The governing equations form a coupled set of partial differential equations that are solved using the Fourier and Laplace integral transformations for the undamped case. The numerical solution is examined for the damped case.
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