The influence of different types of hangers system of steel arch bridges

Abstract

The aim of this paper is to analyse the lateral stability of the Medgidia arch steel bridge upporting live loads consisting of Class E of vehicles (A30, V80) and having different types of hangers systems. For the analysis, the arch bridge was considered in the existing form, in which he was erected and having a Langer system for hangers and supplementary also two Nielsen systems are taked into account: the first system consist in inclined hangers forming a triangular net and the second one consist in inclined crossing hangers. The Lusas Finite Element System was used to perform all the analysis presented in this paper.
In order to establish which is the influence of each hangers system on the general stability of the arch bridge, many types of analysis are made. In the first stage a linear elastic analysis is performed. Further, other types of analysis are made: a linear buckling analysis which give information about the maximum load that can be supported prior to structural instability and a geometrically nonlinear analysis which take into account the effect of structural deformation on structural stiffness. The defomed mesh of the structure resulting from the linear elastic analysis was considered as the starting point for the geometrically nonlinear analysis.
The vehicles acting on the bridge are placed on the deck taking into account the romanian norm specifications from the for road bridges, 3221-86. For this reason, the load consisting în many rows of A30 vehicles has a non-symmetrical position and the load corresponding to V80 vehicle has a symmetrical position on the bridge deck.
Performing a step by step geometrically nonlinear analysis, a series of P-Δ (load-displacement) curves are ploted and from these, the critical buckling load of the arches corresponding to each type of hangers system could be computed.
Finally a comparaison between these load-displacement curves is made, which could give some informations about the influence of each type of hangers system on the general stability of this arch steel bridge.