Influence of eccentric load introduction during launching with rockers using an elastomeric bearing

Abstract

AbstractDuring launching, the superstructure acts as a continuous beam supported by different launching bearings on the piers. Just before reaching the next pier, a part of the superstructure temporarily behaves as a long cantilever. As a result, a large bending moment and reaction force at the last bearing occur. The interaction of the internal forces results in a biaxial stress state in the cross‐section. This load case is usually determining for the buckling check and the structural design of the webs. Additionally, the webs of the superstructure and the launching bearing often fail to share the same center lines. This eccentricity can be caused by misalignments of the launching bearings, the necessary air gap to the lateral guide as well as the different thicknesses of the panels along the superstructure. These eccentricities are not considered in the buckling check according to EN 1993‐1‐5 [1]. It is often discussed how these eccentricities affect the buckling behaviour and whether they must be considered in the buckling check. In the case of launching bearings like a rocker system which includes an elastomeric bearing between the superstructure and the launching beam, the reaction forces of the nonlinear material behaviour are additionally discussed. In [2] the effects on the buckling resistance in dependence of load eccentricity for some parameters for the different types of launching bearings are presented. [3] shows the comparison of the buckling resistance with investigations from [4] and [5] with the buckling check according to [1]. A comprehensive summary and the new proposal for considering an eccentric load application and clamping effects in the buckling zone can be read in [6]. This paper shows first investigations of the influence of the elastomeric bearing and the problem of the reaction of the nonlinear material behaviour and its definition in the numerical model. The results have shown that load eccentricities in combination with elastomeric bearings have no impact on the buckling behaviour.