Issue 48

E. Maiorana, Frattura ed Integrità Strutturale, 48 (2019) 459-472; DOI: 10.3221/IGF-ESIS.48.44 459 Contribution of longitudinal stiffener rigidity and position to bridge girder integrity Emanuele Maiorana OMBA Impianti & Engineering SpA, Via della Croce, 10 – 36040 Torri di Quartesolo (VI), Italy emaior@libero.it , http://orcid.org/0000-0002-3574-1410 A BSTRACT . To increase the elastic critical load of a plate, such as I-shaped cross-welded section of bridge girders and upgrade bending and torsional stiffnesses, slenderness is usually reduced by dividing the web into subpanels, by means of transversal stiffeners and a longitudinal stiffener. The optimal solution is defined when the stiffener maximizes the buckling coefficient, with a minimal cross-section area. For this purpose, seven shapes of open and closed sections of longitudinal stiffeners, with different second moment of area, are examined in terms of buckling coefficients by theoretical solution and numerical computation, to compare their contribution in terms of weight per linear meter of beam. The optimum value of flexural stiffness is defined and a useful practical law is given to correlate the best position of a conventional flat stiffener with respect to variations of the stress gradient, from pure bending to pure compression, to maximize the benefits of its action and increase the stability of bridge girders. K EYWORDS . Bridge stability; Buckling coefficient; Optimal stiffness; Stiffener optimal positioning. Citation: Maiorana, E., Contribution of longitudinal stiffener rigidity and position to bridge girder integrity, Frattura ed Integrità Strutturale, 48 (2019) 459-472. Received: 20.11.2018 Accepted: 28.02.2019 Published: 01.04.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION lender elements are widely used in engineering, as the static inertial characteristics of their sections allow full use of materials by optimization of geometric shapes according also to the external loads to which they are subjected. Generally, to increase the elastic critical load, see e.g. the bridge girders in Fig. 1, slenderness  = h / t , i.e. the ratio between height h and thickness t of the web panel, is reduced by dividing the web into subpanels according to its stiffening system. A major difficulty encountered in the study of stiffened bridge webs subject to non-uniform compression, e.g., high beam web panels subject to bending-compressive loads, is to define a sufficient rigidity and accurate positioning of the longitudinal stiffener, since compression stresses vary linearly along the web. An optimal solution is represented by the solution in which the stiffener maximizes its effect for good web panel resistance at stability, with a minimal cross-section area. S