Determination of gust action stress cycle counts for fatigue checking of line-like steel structures*1

The classical spectral analysis of structural response to a gusty wind is applied to the prediction of fatigue damage as expressed by the rate of accumulation of Minerʹs quotient, using the rainflow algorithm to establish stress-range cycle counts. A general solution in chart form is given for the effect of the broad-band (quasi-static) part of the response spectrum, together with an algebraic formulation for its combination with the effect of narrow-band (quasi-resonant) response. A procedure for integration of the long-term expectation of Minerʹs quotient is indicated. It is concluded that quasi-static response alone is unlikely to pose a serious fatigue problem. With generally anticipated levels of dynamic response, fatigue damage is greatly increased, but can be controlled at acceptable levels by care to avoid features especially sensitive to fatigue.