Standard Towers Research Articles

Experimental evaluation of the compressive resistance of non-stress-relieved solid round steel columns

Solid round steel columns are commonly used as legs and also as diagonal and horizontal members of communication towers. The Canadian standard Antennas, towers, and antenna supporting structures, CSA S37–01, specifies empirical expressions for the compressive resistance of solid round columns based on the Structural Stability Research Council (SSRC) column curves for non solid round columns as well as the results from experimental investigations on solid rounds that have been carried out since 1965. As such, it was felt necessary to conduct an experimental study on non-stress-relieved steel solid round columns to refine the available design equations for such columns. This paper provides a summary of a recent test program on the compressive resistance of non-stress-relieved steel solid rounds. Correlation between the results from these tests and the current practice for the design of solid rounds is investigated. The paper concludes with a proposed compressive resistance equation for economical design of such columns.

Revamping the extraction blocks in vacuum resid deasphalting units

0009-3092/07/4301–0017 © 2007 Springer Science+Business Media, Inc. Deasphalting of vacuum resid with liquefied propane is usually conducted in extraction towers of the gravity type. Standard towers (Fig. 1a) have a small (~7 m) height of the propane and vacuum resid reaction zone and are equipped with baffle trays that consist of metal trays 353 mm wide and 6 mm thick with a step of 68 mm positioned at a 45° angle. This design of the internals insignificantly increases the time the phases are held in the tower and causes formation of “coke” deposits, which are high-melting asphaltite, on the trays. The extraction tower with baffle trays is close to the spray tower in efficiency.

On splitting of totally singular quadratic forms

In this note we completely study the standard splitting of quasi-Pfister forms and their neighbors, and we include some general results on standard splitting towers of totally singular quadratic forms.

Fire-Safety Upgrades in Airport Control Towers

This paper discusses fire-safety upgrades and the various aspects of their design and construction in standard airport traffic control towers (ATCTs) for the Federal Aviation Administration (FAA) in the Western Pacific region. Towers provide a safe and orderly flow of airport traffic for the benefit of the flying public. Knowledge of ATCT fire-safety upgrades can benefit professionals and contractors in various engineering fields, especially those interested in project management and control techniques. Specifically, the successful upgrading of 35 standard towers in the Western Pacific region to provide smoke-free, fire-protected means of egress and early-warning fire detection and alarm system, as specified in FAA's Fire Safety Guidelines , demonstrates how to meet major program objectives within a cost-effective time frame. This paper includes a brief history of the relationship between the FAA and the Technical Support Services Contract as it relates to these upgrades; a general description of the work...

Design of 60° equal-leg steel angles according to CSA Standard S37-94

Sixty-degree equal-leg steel angles find widespread application as leg members of triangular-base lattice towers. Compared to 90° angles of the same size, these angles are weaker in torsional-flexural buckling. The design of such angles is being explicitly covered for the first time in CSA Standard S37-94, "Antennas, towers and antenna-supporting structures." Recent experimental studies have shown that the design of 60° angles will be quite safe, if design is carried out using the expressions for factored axial compressive resistances given in CAN/CSA-S16.1-M89, taking into account only the effect of local buckling and flexural buckling about minor axis, and neglecting torsional-flexural buckling. The Canadian Standards Association Technical Committee on Antenna Towers also noted that the calculated resistances will still be less than the strengths according to the widely used Standard ANSI/ASCE 10-90, "Design of latticed steel transmission structures," which considers all the three modes of buckling. The present paper explains the rationale behind the design procedure adopted by the Technical Committee. Key words: angles, buckling, compression, design strength, schifflerized angles, specifications, steel towers, 60° angles.

An optimal algorithm for Reve's puzzle

This paper starts by showing that some recently published algorithms for Reve's puzzle are not optimal. Reve's puzzle is a generalization of the standard Towers of Hanoi whereby the number of pegs is extended from 3 to k ⩾ 2. A simple and elegant recursive algorithm for solving Reve's puzzle is presented. Its optimality is assured by an algorithm for optimally splitting a tower of n discs into two subtowers. The theoretical basis for doing so is also discussed.

An Algorithmic Solution to the Multi-tower Hanoi Problem

Abstract The Multi-tower Hanoi problem is a generalization of the standard Towers of Hanoi problem, such that the number of pegs is changed from 3 to t, where t ≥ 2. An algorithmic solution to the Multi-tower Hanoi problem is presented. Furthermore, a method is provided for splitting a tower of n discs into two towers having n1 and n2 discs, respectively. Such a method forms the basis for the algorithm to generate the minimum number of moves for transferring a n-disc tower to another peg using t pegs.

The vincent 220-kv. transmission line: Engineering and construction features

This paper deals with the design and construction of the third 220,000-volt line between Los Angeles and Big Creek, giving the results and brief descriptions of the research engineering investigations which were carried out in connection with the design. The salient features of the line are: Terminals — Big Creek No. 3 and Gould Switching Station, near Los Angeles. Length — 223.5 mi. Route — Direct route with few angles. Dead-ends — Dead-ends only at station terminals and heavy angles. Small angles — Small angles up to 11 deg. 40 min., in some cases, turned on suspension insulators. Conductors — Steel reinforced aluminum. 1,033,500 cir. mils aluminum, 54 strands. 134,000 cir. mils steel, 7 strands. Weight: 1.33 lb. per ft. Diameter: 1.247 in. Overhead Ground Wire — None. Towers — Towers of high elastic limit steel. Height of standard towers, 64 ft. to crossarm. Height of anchor tower, 56 ft. to cross-arm. Weight of standard tower, 8890 lb. Weight of anchor tower, 13,600 lb. Tower Footings — Grillage footings in earth. For standard towers, 4 ft. 8 in. sq. at base and 8 ft. deep. Weight, 2040 lb. For anchor towers, 7 ft. 6 in. sq. at base and 9 ft. deep. Weight, 6720 lb. Tower Extensions — Height 7, 14, or 21 ft. Any of these heights may be placed on any or all corners of the tower and in a few special cases in combination with an additional 14-ft. extension on all corners. Insulators — 10-in. cap and pin having minimum combined electrical and mechanical strength of not less than 18,000 lb. Suspension insulator assembly: Single string of 13 units where maximum stress in string will not exceed 6000 lb. Double string 13 units in length where maximum load will exceed 6000 lb. Dead-end assembly: Double string, 15 units in length. Tie-down assembly: Single string of 14 units. Shield Rings — Hoops of 8-in. by 3/16-in. strap iron. Bird Guards — Pans and saw-tooth guards on all towers. Increases in the generator capacity at Big Creek, which are scheduled to be completed in 1928, will require more transmission capacity to deliver the power to Los Angeles. For this reason, a third 220,000-volt line is being built between those points.

The Vincent 220-Kv. Transmission Line Engineering and Construction Features

This paper deals with the design and construction of the third 220,000-volt line between Los Angeles and Big Creek, giving the results and brief descriptions of the research engineering investigations which were carried out in connection with the design. The salient features of the line are: Terminals-Big Creek No. 3 and Gould Switching Station, near Los Angeles. Length-223.5 mi. Route-Direct route with few angles. Dead-ends-Dead-ends only at station terminals and heavy angles. Small angles-Small angles up to 11 deg. 40 min., in some cases, turned on suspension insulators. Conductors-Steel reinforced aluminum. 1,033,500 cir. mils aluminum, 54 strands. 134,000 cir. rails steel, 7 strands. Weight: 1.33 lb. per ft. Diameter: 1.247 in. Overhead Ground Wire-None. Towers-Towers of high elastic limit steel. Height of standard towers, 64 ft. to crossarm. Height of anchor tower, 56 ft. to crossarm. Weight of standard tower, 8890 lb. Weight of anchor tower, 13,600 lb. Tower Footings-Grillage footings in earth. For standard towers, 4ft. 8 in. sq. at base and 8 ft. deep. Weight, 2040 lb. For anchor towers, 7ft. 6 in. sq. at base and 9 ft. deep. Weight, 6720 lb. Tower Extensions-Height 7, 14, or 21 ft. Any of these heights may be placed on any or all corners of the tower and in a few special cases in combination with an additional 14-ft. extension on all corners. Insulators-10-in. cap and pin having minimum combined electrical and mechanical strength of not less than 18,000 lb.

Special features in the design of transmission tower lines as imposed by electrical conditions

This paper is confined to the factors which affect the structural and mechanical phases of transmission line design. These are divided into two groups as follows: 1. Factors affecting design of tower. 2. Features involving location of towers. The writer has in general refrained from commenting on the various items listed. Exceptions are made, however, in certain features which in his opinion deserve particular emphasis. Briefly, these are: 1. The consideration of an “economical stringing stress” as described under “Factors affecting Strength of Tower.” 2. The description of transpositions. 3. Features involving location of towers. Views and diagrams are used to describe the transpositions and a table giving data on the standard towers for the 110-kv. and 220-kv. transmission lines of the Pacific Gas and Electric Company is also included.

Special Features in the Design of Transmission Tower Lines as Imposed by Electrical Conditions

This paper is confined to the factors which affect the structural and mechanical phases of transmission line design. These are divided into two groups as follows: 1. Factors affecting design of tower. 2. Features involving location of towers. The writer has in general refrained from commenting on the various items listed. Exceptions are made, however, in certain features which in his opinion deserve particular emphasis. Briefly, these are: 1. The consideration of an ``economical stringing stress'' as described under ``Factors affecting Strength of Tower.'' 2. The description of transpositions. S. Features involving location of towers. Views and diagrams are used to describe the transpositions and a table giving data on the standard towers for the 110-kv. and 220-kv. transmission lines of the Pacific Gas and Electric Company is also included.

The Necaxa development of the Mexican light and power company

The Necaxa development has its origin in the mountainous regions of Mexico. By an elaborate system of storage reservoirs, dams, dikes, tunnels and inverted steel siphons, extending back into the country 25 miles, the waters of several rivers, including the Necaxa, are diverted into one valley, and there directed onto the turbine wheels which drive the large electrical generators supplying power to the surrounding country. The City of Mexico has approximately 400,000 population, with another 100,000 near by, and it is planned to supply all the electrical needs of this population from the Necaxa development. Perpetual rights have been granted by the Mexican government and many millions of dollars are still to be expended in perfecting the system. Due to the warm gulf winds condensing upon the plateaus there is an average rainfall of 135 inches per year, so that with a large storage system such as is being constructed at Necaxa, the full output of the plants is available throughout the year. The most important of the dams is the Necaxa, which is 190 feet high, being the highest earthen dam in the world. It is 1,000 feet wide at the base, and a quarter of a mile across at the crest. When entirely completed it will be impound 1,590,000,000 cubic feet of water. It will give some idea of the value of every cubic foot of water when it is understood that one cubic foot per second over the Necaxa Falls now means 100 h.p. on the switchboard, and when the system is completed with two other power houses using the same water, one cubic foot per second will mean approximately 300 h.p. The upper Necaxa Falls are 460 feet high, and the lower falls are 740 feet high. The connected load now on the Necaxa lines is 90,000 kw., and it is planned ultimately to take care of 200,000 h.p. The present generating plant consists of six dynamos, each of 6,000 kw. capacity, driven by impulse turbine wheels, which were originally of, 8,200 h.p., but are now rebuilt for 12,000 h.p. Generators of 12,000 kw. capacity are now being built for the Necaxa system. These machines will be able to develop 15,000 kw. continuously, and will be the largest water-driven generators in the world. There will be four nozzles directing water on the buckets of each of the water wheels driving these generators. The transmission system consists of two separate pole lines, each carrying two three-phase circuits. The standard towers are of steel, and are 50 feet high, with a ground wire installed at the top of each tower, and making an equilateral triangle with the wires of the two power circuits. The high tension voltage of the system is 80,000, carried on 18-inch Thomas pin insulators. A telephone line is strung on the same steel towers, and it is stated that no serious disturbances have yet been attributed to the proximity of the power lines.