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Practical approach to optimum design of steel tubular slip-joint power transmission poles

Dicleli, Murat
Nassar, W
Steel tubular poles are employed in large numbers when used for power transmission and consequently their most economical design is desirable. The pole weight affects the overall cost of a system of steel tubular pole structures considering the cumulative effects of material, manufacturing, transportation and erection costs. Therefore, an optimal design may be achieved by designing the lightest possible slip-joint pole which fulfills the geometric and limit states criteria under specified loading conditions. In this research, a computer-aided approach, for the optimum design of steel tabular slip-joint poles is developed. The pole weight is optimized to satisfy the specified geometric limits and limit states design criteria. The optimization procedure uses a simple algorithm to vary the pole diameter and its taper within the specified geometric limits. This results in a total of 121 poles with different geometric properties. For each pole, first the location of the maximum design stresses within each segment of the slip-joint pole is determined. Maximum stresses are then calculated and used to design the poles to satisfy ultimate strength and local buckling criteria. The serviceability limit states criteria for wind-induced vibrations; the effect of wind drag and the second order effects due to the presence of axial loads are included in the analyses. Using the developed optimization algorithm, simple equations and charts are developed for the optimal design of steel tubular slip-joint poles of various steel grade, and length and loading conditions.