Chapter 10. Estimating Stress Intensity Factor for Semi Elliptical Circumferential Cracks in Offshore Wind Turbine Monopiles Using Weight Functions

A methodology for calculating the stress intensity factor (SIF) of an offshore monopile containing a semi-elliptical external surface crack subjected to a complex stress distribution is presented in this paper. The approach is based on the theory of weight functions. The proposed methodology is validated against results presented in literature and also bespoke finite element analysis. The proposed methodology is significantly faster than conventional finite element fracture mechanics analysis. It also produces a more accurate estimation of SIF for monopiles compared against industrial standards such as BS 7910. The near-instantaneous calculation of SIF for any cracked monopile is a significant development in certifying the integrity of aged offshore wind turbine monopiles as it allows the fitness for purpose of the cracked structure to be assessed in pseudo real time.