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Vibration Control
In earthquake engineering, vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building structures. All seismic vibration control devices may be classified as ''passive'', ''active'' or ''hybrid'' where: * ''passive control devices'' have no feedback capability between them, structural elements and the ground; * ''active control devices'' incorporate real-time recording instrumentation on the ground integrated with earthquake input processing equipment and actuators within the structure; * ''hybrid control devices'' have combined features of active and passive control systems. When ground seismic waves reach up and start to penetrate a base of a building, their energy flow density, due to reflections, reduces dramatically: usually, up to 90%. However, the remaining portions of the incident waves during a major earthquake still bear a huge devastating potential. After the seismic waves enter a superstructure, there is a number o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake Engineering
Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake (or seismic) engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. Earthquake engineering is the scientific field concerned with protecting society, the natural environment, and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels. Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismic loading; it is considered as a subset of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in recent earthquakes have led to an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-rise Building
A tower block, high-rise, apartment tower, residential tower, apartment block, block of flats, or office tower is a tall building, as opposed to a low-rise building and is defined differently in terms of height depending on the jurisdiction. It is used as a residential, office building, or other functions including hotel, retail, or with multiple purposes combined. Residential high-rise buildings are also known in some varieties of English, such as British English, as tower blocks and may be referred to as MDUs, standing for multi-dwelling units. A very tall high-rise building is referred to as a skyscraper. High-rise buildings became possible to construct with the invention of the elevator (lift) and with less expensive, more abundant building materials. The materials used for the structural system of high-rise buildings are reinforced concrete and steel. Most North American-style skyscrapers have a steel frame, while residential blocks are usually constructed of concrete ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vibration Isolation
Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations. Vibration is undesirable in many domains, primarily engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Vibrations propagate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others. Passive vibration isolation makes use of materials and mechanical linkages that absorb and damp these mechanical waves. Active vibration isolation involves sensors and actuators that produce disruptive interference that cancels-out incoming vibration. Passive isolation "Passive vibration isolation" refers to vibration isolation or mitigation of vibrations by passive techniques such as rubber pads or mechanical springs, as opposed to "active vibration isolation" or "electronic force cancellation" employing electric power, sensors, actuators, and control systems. Passive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallic Roller Bearing
A metallic roller bearing is a base isolation device which is intended for protection of various building and non-building structures against potentially damaging lateral impacts of strong earthquakes. This bearing support may be adapted, with certain precautions, as a seismic isolator to skyscrapers and buildings on soft ground. Metallic roller bearings are employed by a housing complex (17 stories) in Tokyo, Japan. See also * Earthquake-resistant structures * Elevated building foundation Seismic base isolation, also known as base isolation, or base isolation system, is one of the most popular means of protecting a structure against earthquake forces. It is a collection of structural elements which should substantially decoup ... References Earthquake engineering Seismic vibration control {{architecture-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake-resistant Structures
Earthquake-resistant or aseismic structures are designed to protect buildings to some or greater extent from earthquakes. While no structure can be entirely immune to damage from earthquakes, the goal of earthquake-resistant construction is to erect structures that fare better during seismic activity than their conventional counterparts. According to building codes, earthquake-resistant structures are intended to withstand the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing collapse of the buildings for rare earthquakes while the loss of the functionality should be limited for more frequent ones. To combat earthquake destruction, the only method available to ancient architects was to build their landmark structures to last, often by making them excessively stiff and strong. Currently, there are several design philosophies in earthquake engineering, making use of experimental r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cushioning
Package cushioning is used to protect items during shipment. Vibration and impact shock during shipment and loading/unloading are controlled by cushioning to reduce the chance of product damage. Cushioning is usually inside a shipping container such as a corrugated box. It is designed to absorb shock by crushing and deforming, and to dampen vibration, rather than transmitting the shock and vibration to the protected item. Depending on the specific situation, package cushioning is often between thick. Internal packaging materials are also used for functions other than cushioning, such as to immobilize the products in the box and lock them in place, or to fill a void. Design factors When designing packaging the choice of cushioning depends on many factors, including but not limited to: * effective protection of product from shock and vibration * resilience (whether it performs for multiple impacts) * resistance to creep – cushion deformation under static load * material cost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anti-vibration Compound
An anti-vibration compound is a temperature-resistant mixture of a liquid with fine particles, which is used to reduce oscillations in calender rolls and to dampen vibrations in fabricated structures like machine beds and housings. Use Vibration may limit the performance of a calender or paper machine. It can have numerous sources such as bulk variations in the sheet, bearing problems, or misalignment of the driveshaft. Vibration manifests itself as a high frequency periodic movement of the roll body with an amplitude from less than one to several µm. When anti-vibration compound is introduced to the center bores of the rolls, vibration is transferred from the solid roll structure to the incompressible fluid component of the anti-vibration compound. Its solid particles are less mobile due to their inertia. Thus the fluid is forced to oscillate around the solid components. The flow energy is absorbed by micro eddies by which the vibration is damped. The benefits are a smoothe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Vibration Control
Active vibration control is the active application of force in an equal and opposite fashion to the forces imposed by external vibration. With this application, a precision industrial process can be maintained on a platform essentially vibration-free. Many precision industrial processes cannot take place if the machinery is being affected by vibration. For example, the production of semiconductor wafers requires that the machines used for the photolithography steps be used in an essentially vibration-free environment or the sub-micrometre features will be blurred. Active vibration control is now also commercially available for reducing vibration in helicopters, offering better comfort with less weight than traditional passive technologies. In the past, passive techniques were used. These include traditional vibration dampers, shock absorbers, and base isolation. The typical active vibration control system uses several components: * A massive platform suspended by several activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Snubber
A mechanical snubber is a mechanical device designed to protect components from excess shock or sway caused by seismic disturbances or other transient forces. During normal operating conditions, the snubber allows for movement in tension and compression. When an impulse event occurs, the snubber becomes activated and acts as a restraint device. The device becomes rigid, absorbs the dynamic energy, and transfers it to the supporting structure. The image at right shows an isometric view of one style of mechanical snubber. When a disturbance occurs that exceeds the acceleration threshold of the snubber, the ball screw and drum produce angular momentum to the inertia mass. The inertial resistance of the mass engages the resilient capstan to tighten around a hardened mandrel, which is part of the structural tube. This, in turn, causes restraining force against the rotation of the ball screw. During standard operation, the associated acceleration is far below the threshold limit of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snubber
A snubber is a device used to suppress ("snub") a phenomenon such as voltage transients in electrical systems, pressure transients in fluid systems (caused by for example water hammer) or excess force or rapid movement in mechanical systems. Electrical systems Snubbers are frequently used in electrical systems with an inductive load where the sudden interruption of current flow leads to a large counter-electromotive force: a rise in voltage across the current switching device that opposes the change in current, in accordance with Faraday's law. This transient can be a source of electromagnetic interference (EMI) in other circuits. Additionally, if the voltage generated across the device is beyond what the device is intended to tolerate, it may damage or destroy it. The snubber provides a short-term alternative current path around the current switching device so that the inductive element may be safely discharged. Inductive elements are often unintentional, arising from the curr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moat
A moat is a deep, broad ditch, either dry or filled with water, that is dug and surrounds a castle, fortification, building or town, historically to provide it with a preliminary line of defence. In some places moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer. Historical use Ancient Some of the earliest evidence of moats has been uncovered around ancient Egyptian castles. One example is at Buhen, a castle excavated in Nubia. Other evidence of ancient moats is found in the ruins of Babylon, and in reliefs from ancient Egypt, Assyria, and other cultures in the region. Evidence of early moats around settlements has been discovered in many archaeological sites throughout Southeast Asia, including ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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