Abstract
Patch loading is a predominant load case at incremental bridge launching. Bridge girder webs are frequently provided with longitudinal stiffeners to increase in-service shear and bending strength, and its effect has been included in design codes. However, no straightforward rules are given to account for the influence of such stiffeners on improving the patch loading resistance. This paper presents a review of some available formulae found in the literature to estimate the girder ultimate strength including the provisions of the European, American and Colombian design codes. Additionally, a nonlinear finite element analysis is conducted on three case studies related to actual launched bridges. The case studies are also used to study the influence of the longitudinal stiffener and girder depth on the girder capacity. Different load-displacement responses are observed depending on the girder depth. Finally, the finite element analysis shows to what extent the longitudinal stiffeners can increase the patch loading capacity of bridge girder webs during launching.
Highlights
The presence of a longitudinal stiffener on the ultimate resistance of plate girders under concentrated loads is currently addressed in most of the design codes including the Eurocode 3
This paper presents a review of available formulae found in the technical literature for the estimation of the ultimate strength of steel bridge girders subjected to patch loading
The review included the provisions of the Europeans, American and Colombian design codes
Summary
The presence of a longitudinal stiffener on the ultimate resistance of plate girders under concentrated loads is currently addressed in most of the design codes including the Eurocode 3. Bergfelt (1979) proposed a semi-empirical equation for the consideration of a longitudinal stiffener in the ultimate patch load resistance of plate girders based on the regression analysis of experimental results. By regression analysis of these experimental results the following formula was obtained: It considers the influence of a longitudinal stiffener on the ultimate capacity of patch loaded plates and takes into account for the influence of the ratio flange-to-web thickness and the difference in yield strength between flanges and web. Considering similar assumptions as in the validation performed by Lagerqvist (1998) the finite element analysis made using ABAQUS predicts an ultimate resistance Frl =6411 kN for unstiffened web This result is higher than the one computed by Bergholtz (1994). Note that similar to other cases, the inclusion of the web stiffener increased the girder ultimate resistance by 10% with respect to the unstiffened web
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