Wind and structural modelling for an accurate fatigue life assessment of tubular structures

Based on the joint probability with regard to wind speed and its main direction, the current paper presents a practical and efficient approach for calculating wind induced fatigue of tubular structures, the effects of the wind direction, across wind and wind grid size on the high cycle fatigue of the structure are addressed. In each time step of the dynamic response calculation, the large deformation effects and the wind induced drag forces due to the updated structural deformations are taken into account. It is found that, the directional wind effects on the fatigue damage mainly depend on the orientation of the structure, the location and the support condition of the selected joints, and the relative probability of occurrence for the high winds speed in each direction, etc. Furthermore, the across wind components are proved to be a significant contributor on the fatigue damage and cannot be ignored. The fatigue damage is also found to be rather sensitive to the wind grid size for generating the wind fields. It is also concluded that vibration of each individual member interacts with the global dynamic response and the wind loading, and a fatigue check should therefore be against both individual member and global response. The wind fatigue calculation procedure presented in the current paper has the merit of reducing uncertainties without degrading a required safety level, this may lead to a positive economic impact with regard to construction and maintenance costs. It has been applied on quite a few industry and research projects and can be widely applied on the similar study of structures.