Web buckling, patch loading and launching bridges

The great improvement due to Finite Elements Method in plate buckling analysis together with the introduction of geometrical and material non linearity, brought the designers in front of the possibility of refining the analysis, in particular for webs of I section in plate girders under bridge launching loads. The aim is to get optimal safety coefficients from an accurate and realistic analysis. In this paper the web buckling state of art is reported and the most actual FEM computational instruments are employed to evaluate the results of simple semi-empirical approaches, underlining in a critical way the validity fields and possible uses. A part of the paper deals with theoretical approach to the problem by international codes among with Eurocodes. A new accurate and simple formulation of numerical derivation is reported for the calculation of stability linear elastic critical value in the case of static patch load and an approach for dynamic patch load is discussed looking and reporting the other possible solutions proposed in the few past years by the most eminent researchers.