Failure analysis of the highway sign structure and the design improvement

In this paper failure analysis of the highway sign supporting structure due to wind loading is presented. It is explained why the commonly practiced static strength validation of such structures, under the extreme monotonic wind load, is not sufficient for the design of wind-loaded stationary structures. A reliable procedure, necessary to validate the structural strength under wind loads, must include the structural strength validation under extreme monotonic load as well as the evaluation of fatigue under the stress spectra of the variable service loads. It is described in what manner the service stress spectra can be derived on the basis of the finite element method (FEM) results and the data about wind activity and intensity (duration and frequency, direction, speed). Taking into account the estimated service stress spectra and the data about allowable stresses for welded joints, given in corresponding design codes, the fatigue evaluation and fatigue life prediction for the fractured structure was carried out. Based on the data of the fatigue evaluation, different design variants of the sign supporting structure were analysed and the best option to fulfil the requirements was selected.