Lateral Stability Analysis for Composite Plate Girder Bridges

Abstract

The methods that are currently available in the Eurocodes for the design of bridge plate girders to lateral torsional buckling are outlined and discussed. The inapplicability of the classic elastic critical moment theory for deep girders, which are common in bridge practice, is demonstrated. The simplified method of the equivalent flange in compression is applied instead, and its results are compared with those of specialised software which can accurately predict the elastic critical load of bridge girders. These widely accepted methods of design are compared to a previously published truss model which has been proposed for the simplified, yet accurate, modelling of bridge plate girders. The results of both the critical load and the design load according to the Eurocodes are compared. For the truss model, the general method for the calculation of the design load is used. A variety of cross-sectional dimensions, lateral restraints and bridge configurations is examined. Emphasis is given in a two-span, two-girder steel concrete composite bridge with various bracing configurations, where many aspects of lateral torsional buckling design can be demonstrated. The advantages of the use of a 3D truss model from practicing engineers are discussed.