Author(s)

L. Fr´yba & C. Fischer

Abstract

A new coupled system beam and string, connected together with an elastic layer of Winkler type, is suggested in this paper. The double system presents the dimin-ishing of the response under a moving force in some cases. The theoretical model looks like a Bernoulli-Euler beam with an axial force and a string with a tensile force. The investigated case represents a simple theoretical model of a prestressed bridge. Keywords: complex system beam and string, moving loads, prestressed bridges. 1 Motivation The engineers have tried to diminish the dynamic response of structures for a long time. The elastic bearings or elastic supports provide one of the possibili-ties which can damp the induced vibrations in some cases. They are applied in seismic regions, e.g. in East Asia, [1]. Recently, the triangular falsework has been investigated, [2], for damping and controlling the vibration – a type which was used in the past time. The prestressed beams have often been applied to prestressed bridges where the reinforced concrete beams are stressed by the pretensile strings. The behaviour of such a system do not affect too much their dynamics excepting that the natural frequencies are a little reduced, [3]. On the other hand, several authors have investigated the double system in recent time : two beams, [4] to [7, 11, 12], or two strings, [8] to [10], connected together with an elastic layer of Winkler type. The double system diminishes the amplitudes of vibration in some cases and, thus, brings some advantages.

Keywords

complex system beam and string, moving loads, prestressed bridges.