Guyed Mast Research Articles

The Representation of Cables Subjected to General Loading

This paper is concerned with the development of a general 3D cable element suitable for use in the analysis of cable structures such as guyed masts and underwater cable systems. The element can adequately model structural cables subjected to completely general loading. The loading may be specified as a function of a Lagrangian coordinate along either the strained or the unstrained length of the cable, and/or as a function of the deformed geometry of the cable. This element is particularly suitable for use in situations where there is a strong interaction between the loading and cable profiles. Examples of structures in which such situations arise are subsea cable systems subjected to current loading and guyed masts under the action of wind and ice loading. In the development of the general cable element, two sets of quantities, i.e. equivalent nodal forces and the tangent stiffness relationships, need to be evaluated. Consideration of equilibrium and compatibility conditions together with the constitutive relationship for a single hanging cable subjected to external loading has led to the development of three simultaneous non-linear equations. The unknowns in these equations are determined using the Newton-Raphson technique to obtain the equivalent nodal forces. Initial estimates are found using simple but accurate formulae which have been developed for this purpose. Based on these equations a method for the determination of the tangent stiffness relationship for the general cable element is described. This method is shown to be particularly efficient in terms of computation. In order to demonstrate the versatility of the general cable element it has been used in the analysis of a stay of a guyed mast and an undersea guyed tower.

NON-LINEAR DYNAMIC ANALYSIS OF GUYED MASTS SUBJECTED TO WIND AND GUY R UPTURES.

NON-LINEAR DYNAMIC ANALYSIS OF GUYED MASTS SUBJECTED TO WIND AND GUY R UPTURES.

On the time-domain analysis of wind response of structures

This paper deals with structures in which the dynamic effects of wind actions cannot be neglected and spectral analyses are not practicable, because of the non-linear structural behaviour. Numerical simulation procedures in time domain are increasingly used in such cases: in particular, the simulation of appropriate wind velocity histories at different heights and of the relevant response quantities are discussed here. Two examples of application are also presented, the first to a single-degree-of-freedom structural model, the second to the seven-mass model of a guyed mast.

A simplified method for dynamic analysis of a guyed mast

The dynamic response of a guyed mast is relatively larger than for other structures. Thus a proper evaluation of the dynamic response is of major importance. The proposed simplified method separates the dynamic response into a low-frequency, background region and a high-frequency, resonant region. The background response has been estimated using patch loading. The resonant responses can be taken into account by multiplying the background response by a dynamic magnification factor. This factor depends, in a systematic way, on the average structural properties of the mast. The approach is illustrated by examples, and compared to a statistical method.

The fatigue of structural wire strands

This paper presents the results of a limited series of large scale in-line and bending fatigue tests on socketed structural strands typical of those used as stays for guyed masts and for suspension bridge hangers. The strand, consisting of a group of hard drawn galvanized steel wires laid up helically about a common axis, is terminated by zinc filled conical sockets. The various failure mechanisms, concentrated on the wires close to the socket, are described and discussed. It is concluded that conservative predictions of the in-line fatigue lives of real strands should be possible although further work is needed on bending fatigue.

New instrumentation for the investigation of sediment suspension processes in the shallow marine environment

An instrumentation system has been developed that continuously measures: flow velocity, water depth, and suspended sediment concentration profiles in the nearshore zone. The system consists of four components: (1) an array of electronic sensors, including: an electromagnetic current meter, a surface-piercing resistance wave gauge, and a five-element array of optical back-scatterance sensors; (2) a signal processing electronics unit; (3) a guyed mast support structure; and (4) a data acquisition system. The small size of the sensors and their response characteristics make the array suitable for monitoring sediment transport to within a few centimeters of the bed under moderately large breaking waves (∼2 m). Results from an experiment on an exposed ocean beach on the coast of Washington, U.S.A., indicate that sand suspension events of long duration (15–40 sec) relative to the period of incident waves contribute a significant quantity of sand to the total littoral drift. Work is now in progress to modify the system for self-contained operation on the continental shelf. Field investigations with the modified system will focus on the acquisition of a data set to test the validity of the suspended sediment distribution equation.

Torre TV Emley Moore - Gran Bretaña

The new Emley Moor television tower was built to replace a guyed steel mast which collapsed at the site in March 1969. It is the first tower of its kind in the UK and, at 330 m height, it is the third highest such tower in the world. We describe here the methods of design and the construction which enabled the new broadcasting aerials to be brought into service within nineteen months of the Consulting Engineer's initial briefing from the Client.

Automatic design of guyed masts subject to deflection constraints

AbstractIn the design of a guyed mast the design specification often imposes limits on the allowable deflection of the mast under wind and other lateral loads. While the deflected form of a mast depends on many different design parameters, the guy erection tensions form one of the simplest means of controlling the lateral displacements. The paper describes a procedure for calculating these tensions in the case of a mast required to have a specified set of displacements under a given set of lateral loads. It also discusses the case where specified deflections are not to be exceeded under a number of different loading conditions.

Establishment of new facilities for WWVL and WWVB

A brief report of the new facilities for standard radio broadcast stations WWVL and WWVB is appropriate here for two reasons. First, the organizers of the Symposium on the Ionospheric Propagation of VLF Radio Waves, to which this issue is devoted, graciously allocated a session of the Symposium for the dedication of the new stations. characteristics and accuracy of these broadcasts arc of clear interest as a tool in VLF and LF propagfLtion r esearch. Secondly, in this first issue of the new journal, R adio Science, it is pleasant to stress an example where radio propagation activities and radio standards activities combine so nicely to fall under the broader term, radio science. dedication of the e facilities to the public ser vice was made by A. V. Astin, Director of the National Bureau of Standards. An address, The Presen t Status of National Standard s for the Basic PhysicnJ Quanti ties, by R. D. Huntoon was part of the dedication sessio n. T echnical papers descrip ti \'e of the transmitLer design , the an tenna design, the frequency and Lime con trol system, and the staLion usefulness in proyiding standard frequencies and times were presented, and are listed by Litle elsewhere in this issue. Both stations are located near Ft. Collins, Colo. Station WliVVI.1 broadcasts at 20 kc/s with a design objecti\'e of 50 kw deli\Tered to the antenna and 1.5 kw radiated. Station vYWVB broadcasts at 60 kc/s with a design objective of 50 kw delivered to the antenna and 10 kw radiated, Frequency of both is normally held to within 2 parts in lOll of the United States Frequency Standard. Deviations from the stated frequency are published for users interested in the highest possible accuracy, Frequency control is realized by a 100 mile round trip servo loop between Ft, Collins and Boulder. carrier phases as recei\red at Boulder are compared with the phase of the working atomic frequency standard. Error signals, from both the 20 kc/s and 60 kc/s transmissions, modulate a 50 lI[c/s FM telemetering transmitter at Boulder. These signals are recovered at Ft, Collins and applied to a servo-motor driven resolver at the input of each transmitter. A significant feature is that long term phase coherence of the transmissions with the atomically controlled standards at Boulder is always m.aintained, even through transmitter outages. Each antenna consists of four guyed masts 400 ft high , placed in a diamond arrangement 750 ft wide and 1880 ft long. An insulated network of aluminum. cables is suspended from each group of four masts . A down lead is suspended from the center of the cable network. present computed radiating efficiency is 2.2 percent at 20 kc/s and 24.6 percent at 60 kc/s. operating schedule is to be con tinuous on both frequencies except for reguhLr maintenfLllce periods. Station IVWVL is operated on an experimental program of b roadcasts to facilitate VLF propagation and timing resefLrch, K eyed canier station identification in International Morse Code is used . Time signals on vVvVVB co nsist of seconds pulses of 5 cycles of 1000 cycle, double-sideband amplitude modula tion . On the beginning of ettch minute (,he pulse will be in creased to one-quarter second and on the beginning of eiLch hoUl' the pulse will be thl'eequarters of tL second in dura tion. Modulation of 500 cis is used to identify the stiLtion in In tema tioIliLl Morse Code. Following the s tfttiOll call letters will be ft letter, either M or P (standing for minus or plus), and a Lhree digit number. This informa tion gi \'es the rela t ionship of the carrier frequency to atomic frequency. For instance M 130 m.eans that the carrier frequency is lower by 130 parts in 1010 than the United States Frequency Standard, This offset is incorporated to enable clocks run by the broadcas t frequency to keep time approximating Universal Time which is commonly used over the world. number is broadcast because this figure changes nearly every year and could change more often. It serves as a reminder to the user that the full fLccuracy of the transmissions can only be realized with proper corrections. 60 kc/s signal is provided as a continentftl service of the National Bureau of Standards. 20 kc/s signal is largely experimental. Both signals are now used to steer radio station WWV wi th negligible degradation of accuracy.