Service strength validation of wind-sensitive structures, including fatigue life evaluation

Abstract In this paper the procedure for the service strength validation of stationary structures under wind loading is treated. The procedure includes static strength evaluation under maximum monotonic load and fatigue assessment under variable cyclic wind loads. For the validation of the service strength of a mobile antenna tower placed in the Croatian coastal area, the data related to the wind speed, direction, loads and stresses were measured and analyzed. Analyses of the specific wind load conditions (northerly and southerly winds Bura and Jugo) and resulting stresses show that the stress spectrum shape can be described by mathematical terms based on the Weibull distribution with the shape parameter value of β = 1.5 . The other two spectrum parameters for the fatigue strength evaluation–maximum spectrum value and number of cycles–can be accounted for by the dynamic response of a structure under the specific wind load, obtained by a numerical procedure. Based on the derived stress spectra and corresponding fatigue data (Woehler curve related to local structural notch or structural hot-spot stress), the expected damage accumulation and the durability life are estimated according to the modified Palmgren–Miner damage accumulation hypothesis. The fatigue strength evaluation including durability life estimation, based on structural hot-spot stress, is described for an example of the welded joint of a mobile antenna tower.