Analysis of Rigid Flange of Bridge Truss Girder

Wojciech Siekierski


Contemporary bridge truss girders have usually “W” bracing and spacing of cross beams smaller than spacing of truss nodes. The flange at deck level is loaded at its nodes and between them. It acts as a truss member and as a beam simultaneously. An analysis of the rigid flange in two stages is presented. The first stage of the analysis is aimed at computation of axial forces. Equivalent loading applied at truss nodes and truss member hinged connections are assumed. Ritter’s method is used to compute axial forces in rigid flange members. The second stage of analysis is aimed at computation of bending moments. A model of the rigid flange as a continuous beam on elastic supports with imposed settlements is assumed. In this stage additional model of truss girder as simply supported beam of equivalent moment of inertia is considered as well. Working example of application of presented analysis is given. Two computational models of rigid flange are analysed: model of rigid flange as member of truss girder and model of isolated rigid flange as continuous beam. Data recorded during test loading of two truss bridge spans are used for verification. Modelling isolated rigid flange as continuous beam and classical modelling of truss girder as plane frame provide similar accuracy of assessment of internal forces and vertical displacements distribution in rigid flange.


bridge truss girder; truss rigid flange; braced beam; boundary conditions; test loading

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DOI: 10.3846/bjrbe.2015.20


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