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Responses of towers subjected to pressures from simulated wind records that vary with time are obtained by computer analysis. Parameters and variations include: Power-law vertical wind profile; mean yaw and standard deviation; horizontal zones to permit random velocity and yaw fluctuations; random normal deviates for wind fluctuations; foundation effect; frequency of velocity and yaw fluctuations; damping; rectangular or linearly varying wind pulses. An equivalent single-mass system, with two uncoupled degrees of freedom along mutually perpendicular planes, represents the mathematical model of the actual structure in the analysis. Results from the analyses of three different towers are presented.

Hypothesis presented is that residual lateral compressive stresses may suppress ductility across notch and permit cleavage fracture to occur; theoretical explanation is given; tests made at Brown Univ on precompressed notched plates tested in tension (and on comparable cylinders) are used to check this principle; they provide substantiation within range of specimen geometry used.

A method by which typical frames may be designed for minimum weight to resist ultimate loads on a collapse basis is presented. Simple plastic theory is assumed to apply, although the procedure is such that members subject to axial loads are included. There is no attempt to define an optimum design, except in the sense of minimum weight. Factors such as fabrication costs and deflection limitations have been subordinated to the requirements of minimum weight, although it is realized that minimum weight is not always the most important factor. The proposed method is unique, in that it is a procedure leading directly to the correct minimum weight design without recourse to trial mechanisms, load interaction curves, or design charts that characterize existing procedures.