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Response Of A Double System Beam And String With An Elastic Layer To The Dynamic Excitations


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L. Frýba, C. Fischer & Sh. Urushadze


The beam with an axial force is coupled with the pretensiled string by an elastic layer of Winkler type. It is subjected to a row of moving forces. The theoretical model corresponds to a prestressed bridge. The governing equations form a coupled set of partial differential equations which are solved using the Fourier and Laplace-Carson integral transformation methods. A simple experimental model was constructed in a form of a plexiglass beam and two strings bound together with several spring and damping elements. The beam was excited by an electro-magnetic exciter and its response was measured at several places. Three steps of stiffness and damping characteristics of the elastic layer were proved to show their effect on the dynamic response of the double system. Its low response is searched. Keywords: prestressed beam, string, dynamic excitation. 1 Introduction Many years standing effort has been devoted to damp the dynamic effects of both the highway and railway vehicles when they cross a bridge. For that purpose, a lot of systems were developed, e.g. elastic supports of bridges, triangular falsework system with controlled damping, double systems with two beams or two strings connecting together with an elastic layer, etc. They are briefly described in [1] and cited in details in [2] and [3]. They are, especially, the papers of Kawanazoe et al. [4] and Oniszczuk [5], who firstly introduced the double beam and double string system, respectively. However, each of the systems mentioned above shows its technical or economic effectiveness only in some specific conditions.


prestressed beam, string, dynamic excitation.