Safety Estimation of the Plate-Girder Structures with Uncertain Parameters from the Shakedown Theory Point of View

A numerical approach to safety estimation of the plate-girder bending structures from the shakedown theory point of view is considered. In the analysis the uncertainties of the physical and geometrical structure’s parameters and also the load parameters have been taken into account. It has been assumed that the structure is subjected to the dead load and variable live loads. The structure’s parameters uncertainties as well as the load magnitude are treated as fuzzy variables or mutually independent random variables. On the basis of the theory of the yield lines and the kinematic formulation of the shakedown problem the limit state function is being built. From this follows that some structural and material parameters such as the plate thickness, plate reinforcement, girder cross sections and yield point are hidden in the limit moments. In case of describing the load parameters by random variables as the safety measure the Hasofer-Lind reliability index is chosen. If all uncertain parameters which appear in the limit state functions are treated as fuzzy variables the dominant failure mechanism and the minimum load factor for the non-shakedown which correspond to them can be obtained by applying -level optimization. The shakedown analysis of a two-span plate-girder has been done and the results have been presented. The main advantage of presented method is that it can be applied without a need for developing special software. It seems to be an effective approach to safety analysis of industrial roof and highway bridges.