TWI Industrial Member Report Summary 35/1977
By C F Boulton and D B Chadwick
The Welding Institute was recently presented with an opportunity to carry out a deterministic fatigue analysis of a slender mast structure, containing a pre-existing crack-like defect, subject to wind loading. Based upon statistical concepts and a number of engineering assumptions, a method of predicting fatigue life in terms of cycles and time to failure was developed. This method employed current research philosophy for dealing with fatigue under random loading conditions and:
a. Experimentally derived stress data from a dynamic strain gauge survey of the structure in question.
b. Data regarding wind speed and frequency of occurrence from Meteorological Office sources.
c. Rainflow stress counting.
d. Linear elastic fracture mechanics, and
e. Non-propagating crack theory.
The potential usefulness of the analysis method for fatigue life prediction of other structures, components or joints subject to random forcing functions is briefly discussed, together with the inherent difficulties of using a deterministic, rather than probabilistic approach.