Conference Paper

Web Post Buckling Resistance of Longitudinally Stiffened Plate Girders

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... This relatively elaborate procedure is similar to an approach recommended by Hendy and Murphy (2007), and is believed to provide a reasonable estimate of the worst-case geometric imperfections for calculation of the "true Rb" of the test girders. The base web out-of-flatness shown in Fig. 4(a) is used as the starting point for the above analyses after conducting imperfection sensitivity studies (Subramanian and White 2014) with various base imperfection patterns and magnitudes. ...
... The residual stresses used in the studies are shown in Fig. 5. Residual stresses in the slender webs are neglected as they are small enough to cause negligible effect on the flexural capacities of slender web longitudinally stiffened plate girders (Subramanian and White 2014). The flange residual stress distribution is based on the Best-Fit Prawel pattern (Kim 2010). ...
... In the following figures and discussions, Mmax refers to the flexural capacity obtained from FE test simulations, Mn EC refers to the capacity calculated using the Eurocode EN 1993-1-1 (CEN 2005) and EN 1993-1-5 (CEN 2006 provisions, Mn AASHTO (Rb based on Fyc) is the capacity computed using the current AASHTO provisions including Rb as calculated by AASHTO, as well as using the elastic section modulus that includes the longitudinal stiffener, Mn AASHTO (Rb = 1.0) is the same calculation but taking Rb = 1.0, and Mn Proposed is the result from the proposed model described in Section 4.1. In these figures, the data points that correspond to the "plateau resistance" are obtained from the results in Subramanian and White (2014). The Commentary to Article 6.10.1.10.2 of the AASHTO LRFD Specifications permits the use of the compression flange stress at the governing strength condition in place of Fyc in the calculation of Rb in case of LTB or FLB, when the compression flange stress is smaller than Fyc. ...
... To determine the most critical initial geometric imperfection seed that may be experienced by the test girders, detailed imperfection sensitivity analyses for various base imperfection patterns were performed in Abaqus for the condition of pure bending. The imperfection sensitivity studies are described in Subramanian and White (2014). The pattern shown in Fig. 1 is similar to the geometric imperfections measured by Vigh and Dunai (2010), and is found to be an appropriate base pattern for use in the test simulations. ...
... The residual stresses used in these studies are shown in Fig. 2. Residual stresses in the web are neglected because they are small enough to cause a negligible effect on the flexural capacities in slender-web longitudinally stiffened plate girders (Subramanian and White 2014). The flange residual stress distribution is based on the best-fit Prawel pattern (Kim 2010). ...
Article
The current AASHTO specification requirements for the web bend-buckling strength reduction factor Rb do not consider the influence of longitudinal stiffeners on the flexural resistance of steel I-girders subsequent to the theoretical bend-buckling of a slender web. This is a deficiency that can have significant impact, especially in regions of continuous-span girders subjected to negative moment. This paper evaluates the contribution of single web longitudinal stiffeners to the yield limit state flexural resistance of slender-web steel I-girders, often referred to as the “plateau” resistance for the lateral torsional and flange local buckling limit states. Based on test simulation studies, the authors recommend a cross-section model that captures the response of the postbuckled web for both homogenous and hybrid girders subjected to uniform moment. The proposed model offers up to 60% improvement relative to the current AASHTO Specifications.
... This procedure is described in detail in the companion paper (Subramanian and White 2016a). The base web out-of-flatness shown in Fig. 2(a) is used as the starting point for the aforementioned analyses after conducting imperfection sensitivity studies with various base imperfection patterns and magnitudes (Subramanian and White 2014). ...
Article
The current AASHTO Specifications impose a penalty on the strengths corresponding to the compression flange in slender web cross sections due to bend-buckling of web in flexural compression. This web bend-buckling factor, Rb¬, does not account for any potential benefits from the influence of web longitudinal stiffening. In a companion paper, the authors have developed a cross-section model that can be used to estimate the flexural capacity of I-girders at the yield limit state. In this paper, an improved handling of combined web bend-buckling and lateral torsional buckling (LTB) of longitudinally stiffened I-girders is proposed based on finite element test simulations. Results from the proposed prediction model are compared to available experimental tests. In addition, the Rb calculated from the proposed model, used in conjunction with the current Specification flange local buckling equations, is shown to provide an improved characterization of the flange local buckling (FLB) capacity of these types of members.
Article
The paper describes the main features and advantages of Eurocode standard EN 1993-1-5 devoted to the design of plated structures. For unstiffened and longitudinally stiffened panels loaded with longitudinal compression stresses all three design approaches, the effective width method, the reduced stress method and numerical simulations based on FEM, are described and commented. With the help of numerical examples on plates with one and four longitudinal stiffeners in pure compression and on a plate girder with one stiffener in the compression zone a comparison among the methods is presented and some possible simplifications of the design procedure are commented. For plates in compression the effective width method and the reduced stress method give very similar results that are also in good correlation to the results of numerical simulations. For plate girders in bending the reduced stress method becomes over-conservative because it does not take account of the stress redistribution. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
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