Self-supporting Towers Research Articles

Efficient matrix techniques applied to transmission tower design

Self-supporting transmission towers are highly indeterminate structures. Until recently, analysis of such structures was accomplished by determinate methods due to the number of calculations involved in indeterminate methods. Results from the former were often questionable because elastic properties of members were not considered. Today, large numerical problems are being solved with high-speed digital computers as a matter of routine. This paper presents a technique for efficiently solving large systems of symmetrical linear equations obtained from an indeterminate method of analysis without resorting to matrix inversion. A procedure for incorporating the analysis into a tower design program is then given.

Tennessee Valley Authority's 500-kY System -Transmission Line Design

The Tennessee Valley Authority (TVA) recently completed construction of an approximately 155-mile 500-kV transmission line, which began commercial operation May 15, 1965. Principal features of the line, which consists of three conductors per phase supported by a free-swinging string of 24 ball-and-socket insulators, are described here. Rigid aluminum alloy spacers maintain the equilateral configuration, and two Alumoweld ground wires, insulated from the towers to provide for future communication channels, serve as shielding for the line. The square-base, waisted, self-supporting steel towers have a minimum 40-foot phase spacing.

A Study or the Use of Aluminum Guyed Towers for Extra-High-Voltage Transmission Systems

Detailed studies carried out by the authors indicate that for the topographic conditions in central British Columbia in Canada, the use of guyed transmission structures offers worthwhile savings over use of conventional self-supporting towers for extra-high-voltage (EHV) transmission systems. However, the self-supporting tower is recommended for the mountain sections of British Columbia. The advantages and disadvantages of both types of structure are considered, together with a description of a series of tests carried out on a guyed aluminum tower to determine erection methods and costs and to evaluate stability under various loading conditions.

Sleet Removal from Antennas

A method is described for automatically releasing the antenna wires in case of excessive sleet load. Should the wires break under a heavy coating of ice, serious damage to the self-supporting towers would result, due to the unbalanced load. It also describes a new type of suspension condenser developed for the sole purpose of preventing the low frequency energy going to the ground and thus making it possible to melt sleet from the individual antenna wires of the multiple tuned antenna without the use and inconvenience of complicated switching at each ground point. The mechanical as well as the electrical design of this condenser is unique. Further, it is believed that dynotrips and pliotrips can be adopted to power transmission lines in such a way as to prevent a big percentage of interruptions. These pieces of apparatus can be so arranged as automatically to introduce into the lines at intervals, additional lengths of conductor and thus increase the sag. It is expected that for long spans over canyons, these would be almost indispensable.

The Development of the Standard Design for Self-Supporting Radio Towers for the United Fruit and Tropical Radio Telegraph Companies

This paper is an historical review of the United Fruit Company's Radio Towers, and describes the origin of a 1906 design for 200 ft. (61 m.) towers; of 50 ft. (15 m.) extension added in 1910; of the hurricane wrecks of 1914, 1915, and 1916, of data deduced from them, and of the reconstruction of the towers. It discusses the effect of a new policy that "radio communication should be made so reliable that, when all other means fail, the public can confidently look to the radio stations to maintain service, which can be done if only the towers remain standing." The preliminary designs for three-legged towers made in 1915 are described, and their economy and advantages as compared with four-legged towers, the saving due to adjustable rod bracing and the low cost of shop work effected by making all leg sections equal short chords of a circular arc, are pointed out. The design of the Tegucigalpa (Honduras) towers, with antenna bridges and the latest revised, "Standard Plan of 400 ft (122 m.) self-supporting towers, with 150 ft. (46 m.) antenna bridges," are shown with the specified loads, unit stresses, and notes on the most favorable direction of wire pull in relation to cross-section of tower. The design of sections and details are briefly referred to, with the limiting heights of towers to which similar sections are applicable. Two pairs of 100 ft. (30.5 m.