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Stockbridge Damper
A Stockbridge damper is a tuned mass damper used to suppress wind-induced vibrations on slender structures such as overhead power lines, long cantilevered signs and cable-stayed bridges. The dumbbell-shaped device consists of two masses at the ends of a short length of cable or flexible rod, which is clamped at its middle to the main cable. The damper is designed to dissipate the energy of oscillations in the main cable to an acceptable level. Wind-induced oscillation Wind can generate three major modes of oscillation in suspended cables: * Gallop has an amplitude measured in metres and a frequency range of 0.08 to 3 Hz * Aeolian vibration (sometimes termed flutter) has an amplitude of millimetres to centimetres and a frequency of 3 to 150 Hz * Wake-induced vibration has an amplitude of centimetres and a frequency of 0.15 to 10 Hz The Stockbridge damper targets oscillations due to aeolian vibration; it is less effective outside this amplitude and frequency ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overhead Power Line
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-phase power) suspended by towers or poles. Since most of the insulation is provided by the surrounding air, overhead power lines are generally the least costly method of power transmission for large quantities of electric energy. Construction Towers for support of the lines are made of wood either grown or laminated, steel or aluminum (either lattice structures or tubular poles), concrete, and occasionally reinforced plastics. The bare wire conductors on the line are generally made of aluminum (either plain or reinforced with steel or composite materials such as carbon and glass fiber), though some copper wires are used in medium-voltage distribution and low-voltage connections to customer premises. A major goal of overhead power line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuned Mass Damper
A tuned mass damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce mechanical vibrations, consisting of a mass mounted on one or more damped springs. Its oscillation frequency is tuned to be similar to the resonant frequency of the object it is mounted to, and reduces the object's maximum amplitude while weighing much less than it. TMDs can prevent discomfort, damage, or outright structural failure. They are frequently used in power transmission, automobiles and buildings. Principle Tuned mass dampers stabilize against violent motion caused by harmonic vibration. They use a comparatively lightweight component to reduce the vibration of a system so that its worst-case vibrations are less intense. Roughly speaking, practical systems are tuned to either move the main mode away from a troubling excitation frequency, or to add damping to a resonance that is difficult or expensive to damp directly. An example of the latt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tacoma Narrows Bridge (1940)
The 1940 Tacoma Narrows Bridge, the first Tacoma Narrows Bridge, was a suspension bridge in the U.S. state of Washington that spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed into Puget Sound on November 7 of the same year. The bridge's collapse has been described as "spectacular" and in subsequent decades "has attracted the attention of engineers, physicists, and mathematicians". Throughout its short existence, it was the world's third-longest suspension bridge by main span, behind the Golden Gate Bridge and the George Washington Bridge. Construction began in September 1938. From the time the deck was built, it began to move vertically in windy conditions, so construction workers nicknamed the bridge Galloping Gertie. The motion continued after the bridge opened to the public, despite several damping measures. The bridge's main span finally collapsed in winds on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guy-wire
A guy-wire, guy-line, guy-rope, or stay, also called simply a guy, is a tensioned cable designed to add stability to a free-standing structure. They are used commonly for ship masts, radio masts, wind turbines, utility poles, and tents. A thin vertical mast supported by guy wires is called a guyed mast. Structures that support antennas are frequently of a lattice construction and are called " towers". One end of the guy is attached to the structure, and the other is anchored to the ground at some distance from the mast or tower base. The tension in the diagonal guy-wire, combined with the compression and buckling strength of the structure, allows the structure to withstand lateral loads such as wind or the weight of cantilevered structures. They are installed radially, usually at equal angles about the structure, in trios and quads. As the tower leans a bit due to the wind force, the increased guy tension is resolved into a compression force in the tower or mast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cable-stayed Bridge
A cable-stayed bridge has one or more ''towers'' (or ''pylons''), from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly. Cable-stayed bridges were being designed and constructed by the late 16th century, and the form found wide use in the late 19th century. Early examples, including the Brooklyn Bridge, often combined features from both the cable-stayed and suspension designs. Cable-stayed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catenary
In physics and geometry, a catenary (, ) is the curve that an idealized hanging chain or cable assumes under its own weight when supported only at its ends in a uniform gravitational field. The catenary curve has a U-like shape, superficially similar in appearance to a parabola, which it is not. The curve appears in the design of certain types of arches and as a cross section of the catenoid—the shape assumed by a soap film bounded by two parallel circular rings. The catenary is also called the alysoid, chainette, MathWorld or, particularly in the materials sciences, funicular. Rope statics describes catenaries in a classic statics problem involving a hanging rope. Mathematically, the catenary curve is the graph of the hyperbolic cosine function. The surface of revolution of the catenary curve, the catenoid, is a minimal surface, specifically a minimal surface of revolution. A hanging chain will assume a shape of least potential energy which is a catenary. Galil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anti-node
A node is a point along a standing wave where the wave has minimum amplitude. For instance, in a vibrating guitar string, the ends of the string are nodes. By changing the position of the end node through frets, the guitarist changes the effective length of the vibrating string and thereby the note played. The opposite of a node is an anti-node, a point where the amplitude of the standing wave is at maximum. These occur midway between the nodes. Explanation Standing waves result when two sinusoidal wave trains of the same frequency are moving in opposite directions in the same space and interfere with each other. They occur when waves are reflected at a boundary, such as sound waves reflected from a wall or electromagnetic waves reflected from the end of a transmission line, and particularly when waves are confined in a resonator at resonance, bouncing back and forth between two boundaries, such as in an organ pipe or guitar string. In a standing wave the nodes are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insulator String
An electrical insulator is a material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—semiconductors and conductors—conduct electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors. The most common examples are non-metals. A perfect insulator does not exist because even insulators contain small numbers of mobile charges (charge carriers) which can carry current. In addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the breakdown voltage of an insulator. Some materials such as glass, paper and PTFE, which have high resistivity, are very good electrical insulators. A much larger class of materials, even though they may have lower bulk resistiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philip Dulhunty
Philip Wellesley Dulhunty, OAM (27 April 1924 - 29 November 2020) was an Australian aviator, power distribution entrepreneur and inventor. He invented the widely-adopted "dogbone" damper for the protection of overhead power lines and produced the world's first battery-powered laptop computer. He was chairman of the Australian National Committee of the Conseil International des Grands Réseaux Électriques (CIGRÉ) and a member of its international administrative council and executive committee. He formed the Seaplane Pilots Association of Australia in 1972 and was its chairman for 44 years. Early life Dulhunty was born in Kempsey, New South Wales, in 1924, great-grandson to Robert Venour Dulhunty, the first white settler of what was to become the city of Dubbo, New South Wales. He was one of five children born to Robert Dulhunty and Phyllis. At age six, the family moved to Port Macquarie where Dulhunty left school after completing his Form Three Intermediate Exam, no high ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vibration Dampers, Severn Bridge
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, such as the movement of a tire on a gravel road. Vibration can be desirable: for example, the motion of a tuning fork, the reed in a woodwind instrument or harmonica, a mobile phone, or the cone of a loudspeaker. In many cases, however, vibration is undesirable, wasting energy and creating unwanted sound. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations could be caused by imbalances in the rotating parts, uneven friction, or the meshing of gear teeth. Careful designs usually minimize unwanted vibrations. The studies of sound and vibration are closely related. Sound, or pressure waves, are generated by vibrating structures (e.g. vocal cords); th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stockbridge Damper POV
Stockbridge may refer to: Places United Kingdom * Stockbridge, Edinburgh, a suburb of Edinburgh, Scotland * Stockbridge, Hampshire * Stockbridge, West Sussex * Stockbridge Anticline, one of a series of parallel east–west trending folds in the Cretaceous chalk of Hampshire * Stockbridge Village, Liverpool * Stockbridge (UK Parliament constituency) United States * Stockbridge, Georgia * Stockbridge, Massachusetts * Stockbridge, Michigan * Stockbridge Township, Michigan * Stockbridge, New York * Stockbridge, Vermont * Stockbridge, Wisconsin * Stockbridge (town), Wisconsin * Stockbridge Bowl, artificially impounded body of water north of Stockbridge, Massachusetts * Stockbridge Falls, a waterfall located on Oneida Creek southwest of Munnsville, New York Structures * Stockbridge Casino, a historic building in Stockbridge, Massachusetts * Stockbridge House, historic building in Colorado Springs, Colorado, a.k.a. Amarillo Motel * Stockbridge High School, a high school in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Stick
In the electric power distribution industry, a hot stick is an insulated pole, usually made of fiberglass, used by electric utility workers when engaged on live-line working on energized high-voltage electric power lines, to protect them from electric shock. Depending on the tool attached to the end of the hot stick, it is possible to test for voltage, tighten nuts and bolts, apply tie wires (twisted lengths of ductile wire which fasten the running cable to its supporting insulators), open and close switches, replace fuses, lay insulating sleeves on wires, and perform various other tasks while not exposing the crew to a large risk of electric shock. Hot sticks are made in different lengths, from simple sticks to telescoping models. Because the fiberglass provides electrical insulation, the hot stick allows utility workers to perform operations on power lines safely without de-energizing them or while the state of the power line is not yet known. This is essential because c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
