Abstract: The in-plane buckling safety of network arch bridges is studied in seven bridges according to the procedures recommended in the European bridge design codes. The safety is assessed by second order analysis with equivalent geometric imperfection. The buckling mode shape and the imperfection amplitude are established according to two different methods and varied in a parametric and a sensitivity study. It is concluded that the most appropriate method for the buckling mode shape calculation of network arches uses a geometrically nonlinear load?displacement analysis with subsequent eigenvalue analysis. Furthermore, the imperfection amplitudes obtained from the two methods of the European design codes show large differences, while the geometric imperfections measured in real bridges are in between them. If most conservative amplitude recommendations are used, the in-plane buckling may become design controlling. The amplitude should be chosen as a reasonable value between the two design code recommendations and considering the characteristics of the actual bridge.

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