A gabion is a cage, cylinder, or box filled with rocks, concrete, or sometimes sand and soil for use in civil engineering, road building, military applications and landscaping. For erosion control, caged riprap is used, for dams or in foundation construction, cylindrical metal structures are used. In a military context, earth- or sand-filled gabions are used to protect sappers, leonardo da Vinci designed a type of gabion called a Corbeille Leonard for the foundations of the San Marco Castle in Milan. Other uses include retaining walls, noise barriers, temporary walls, silt filtration from runoff, for small or temporary/permanent dams, river training. They may be used to direct the force of a flow of water around a vulnerable structure. Gabions are used as fish screens on small streams, a gabion wall is a retaining wall made of stacked stone-filled gabions tied together with wire. Gabion walls are usually battered, or stepped back with the slope, gabion baskets have some advantages over loose riprap because of their modularity and ability to be stacked in various shapes.
Gabions have advantages over more rigid structures, because they can conform to subsidence, dissipate energy from flowing water and resist being washed away and their strength and effectiveness may increase with time in some cases, as silt and vegetation fill the interstitial voids and reinforce the structure. They are sometimes used to prevent falling stones from a cut or cliff endangering traffic on a thoroughfare, the life expectancy of gabions depends on the lifespan of the wire, not on the contents of the basket. The structure will fail when the wire fails, galvanized steel wire is most common, but PVC-coated and stainless steel wire are used. PVC-coated galvanized gabions have been estimated to survive for 60 years, Some gabion manufacturers guarantee a structural consistency of 50 years. In the United States, gabion use within streams first began with projects completed from 1957 to 1965 on North River and Zealand River, more than 150 grade-control structures, bank revetments and channel deflectors were constructed on the two U. S.
Forest Service sites. Eventually, a portion of the in-stream structures failed due to undermining. In particular and abrasion of wires by bedload movement compromised the structures, other gabions were toppled into channels as trees grew and enlarged on top of gabion revetments, leveraging them toward the river channels. Gabions have used in building, as in the Dominus Winery in the Napa Valley, California by architects Herzog & de Meuron. There are various designs of gabions to meet particular functional requirements. For example, Bastion, a gabion lined internally with a membrane, typically of nonwoven geotextile to permit use of a granular soil fill, mattress, a form of gabion with relatively small height relative to the lateral dimensions, commonly very wide. For protecting surfaces from wave erosion and similar attack, rather than building or supporting high structures, trapion, a form of gabion with a trapezoidal cross section, designed for stacking to give a face that is sloping rather than stepped
Fluid statics or hydrostatics is the branch of fluid mechanics that studies incompressible fluids at rest. It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics, hydrostatics are categorized as a part of the fluid statics, which is the study of all fluids, incompressible or not, at rest. Hydrostatics is fundamental to hydraulics, the engineering of equipment for storing and using fluids and it is relevant to geophysics and astrophysics, to meteorology, to medicine, and many other fields. Some principles of hydrostatics have been known in an empirical and intuitive sense since antiquity, by the builders of boats, cisterns and fountains. Archimedes is credited with the discovery of Archimedes Principle, which relates the force on an object that is submerged in a fluid to the weight of fluid displaced by the object. The fair cup or Pythagorean cup, which dates from about the 6th century BC, is a technology whose invention is credited to the Greek mathematician.
It was used as a learning tool, the cup consists of a line carved into the interior of the cup, and a small vertical pipe in the center of the cup that leads to the bottom. The height of this pipe is the same as the line carved into the interior of the cup, the cup may be filled to the line without any fluid passing into the pipe in the center of the cup. However, when the amount of fluid exceeds this fill line, due to the drag that molecules exert on one another, the cup will be emptied. Herons fountain is a device invented by Heron of Alexandria that consists of a jet of fluid being fed by a reservoir of fluid. The fountain is constructed in such a way that the height of the jet exceeds the height of the fluid in the reservoir, the device consisted of an opening and two containers arranged one above the other. The intermediate pot, which was sealed, was filled with fluid, trapped air inside the vessels induces a jet of water out of a nozzle, emptying all water from the intermediate reservoir.
Pascal made contributions to developments in both hydrostatics and hydrodynamics, due to the fundamental nature of fluids, a fluid cannot remain at rest under the presence of a shear stress. However, fluids can exert pressure normal to any contacting surface, if a point in the fluid is thought of as an infinitesimally small cube, it follows from the principles of equilibrium that the pressure on every side of this unit of fluid must be equal. If this were not the case, the fluid would move in the direction of the resulting force, the pressure on a fluid at rest is isotropic, i. e. it acts with equal magnitude in all directions. This characteristic allows fluids to transmit force through the length of pipes or tubes, i. e. a force applied to a fluid in a pipe is transmitted, via the fluid, to the other end of the pipe. This principle was first formulated, in an extended form, by Blaise Pascal. In a fluid at rest, all frictional and inertial stresses vanish, when this condition of V =0 is applied to the Navier-Stokes equation, the gradient of pressure becomes a function of body forces only
Groundwater is the water present beneath Earths surface in soil pore spaces and in the fractures of rock formations. A unit of rock or a deposit is called an aquifer when it can yield a usable quantity of water. The depth at which pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the naturally, natural discharge often occurs at springs and seeps. Groundwater is withdrawn for agricultural and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earths subsurface contains some water, Groundwater may not be confined only to Earth. The formation of some of the landforms observed on Mars may have influenced by groundwater. There is evidence that water may exist in the subsurface of Jupiters moon Europa.
Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water, therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of water storage in the United States. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, many municipal water supplies are derived solely from groundwater. Polluted groundwater is less visible, but more difficult to clean up, than pollution in rivers, Groundwater pollution most often results from improper disposal of wastes on land. An aquifer is a layer of substrate that contains and transmits groundwater. When water can flow directly between the surface and the zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are more saturated since gravity causes water to flow downward. The upper level of this layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone, substrate with low porosity that permits limited transmission of groundwater is known as an aquitard
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 such structures more resistant to earthquakes. An earthquake engineer aims to construct structures that will not be damaged in minor shaking, the main objectives of earthquake engineering are, Foresee the potential consequences of strong earthquakes on urban areas and civil infrastructure. Design and maintain structures to perform at earthquake exposure up to the expectations, a properly engineered structure does not necessarily have to be extremely strong or expensive. It has to be designed to withstand the seismic effects while sustaining an acceptable level of damage. Seismic loading means application of an earthquake-generated excitation on a structure and it happens at contact surfaces of a structure either with the ground, with adjacent structures, or with gravity waves from tsunami. The loading that is expected at a location on the Earths surface is estimated by engineering seismology.
It is related to the hazard of the location. Earthquake or seismic performance defines an ability to sustain its main functions, such as its safety and serviceability, at. A structure is considered safe if it does not endanger the lives. A structure may be considered if it is able to fulfill its operational functions for which it was designed. On the other hand, it should remain operational for more frequent, engineers need to know the quantified level of the actual or anticipated seismic performance associated with the direct damage to an individual building subject to a specified ground shaking. Such an assessment may be performed either experimentally or analytically, Experimental evaluations are expensive tests that are typically done by placing a model of the structure on a shake-table that simulates the earth shaking and observing its behavior. Such kinds of experiments were first performed more than a century ago, only recently has it become possible to perform 1,1 scale testing on full structures.
Due to the nature of such tests, they tend to be used mainly for understanding the seismic behavior of structures, validating models. Thus, once validated, computational models and numerical procedures tend to carry the major burden for the seismic performance assessment of structures. The technique as a concept is a relatively recent development. In general, seismic structural analysis is based on the methods of structural dynamics, for decades, the most prominent instrument of seismic analysis has been the earthquake response spectrum method which contributed to the proposed building codes concept of today
Drainage is the natural or artificial removal of surface and sub-surface water from an area. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging, all houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered drains, which lined the major streets, the invention of hollow-pipe drainage is credited to Sir Hugh Dalrymple, who died in 1753. New drainage systems incorporate geotextile filters that retain and prevent fine grains of soil from passing into, geotextiles are synthetic textile fabrics specially manufactured for civil and environmental engineering applications. Geotextiles are designed to retain fine soil particles while allowing water to pass through, in a typical drainage system they would be laid along a trench which would be filled with coarse granular material, sea shells, stone or rock. The geotextile is folded over the top of the stone, groundwater seeps through the geotextile and flow within the stone to an outfell.
In high groundwater conditions a perforated pipe is laid along the base of the drain to increases the volume of water transported in the drain. Alternatively, the prefabricated plastic drainage system made of HDPE called SmartDitch, often incorporating geotextile, over the past 30 years geotextile and PVC filters have become the most commonly used soil filter media. They are cheap to produce and easy to lay, with factory controlled properties that ensure long term filtration performance even in fine silty soil conditions, seattles Public Utilities created a pilot program called Street Edge Alternatives Project. The project focuses on designing a system to provide drainage that more closely mimics the natural landscape prior to development than traditional piped systems, the streets are characterized by ditches along the side of the roadway, with plantings designed throughout the area. An emphasis on non curbed sidewalks allows water to more freely into the areas of permeable surface on the side of the streets.
Because of the plantings the run off water from the area does not all directly go into the ground. Sustainable Urban Drainage Systems are designed to encourage contractors to install drainage system that closely mimic the natural flow of water in nature. Since 2010 local and neighbourhood planning in the UK is required by law to factor SUDS into any development projects that they are responsible for, slot drainage has proved the most breakthrough product of the last twenty years as a drainage option. Both stainless steel and concrete channel slot drainage have become industry standards on construction projects, the civil engineer is responsible for drainage in construction projects. They set out from the all the roads, street gutters, culverts. During the construction process he/she will set out all the levels for each of the previously mentioned factors. Civil engineers and construction managers work alongside architects and supervisors, quantity surveyors, most jurisdictions have some body of drainage law to govern to what degree a landowner can alter the drainage from his parcel
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction, Dry friction resists relative lateral motion of two surfaces in contact. Dry friction is subdivided into static friction between non-moving surfaces, and kinetic friction between moving surfaces, fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces, skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. Internal friction is the force resisting motion between the making up a solid material while it undergoes deformation. When surfaces in contact move relative to other, the friction between the two surfaces converts kinetic energy into thermal energy. This property can have consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire.
Kinetic energy is converted to thermal energy whenever motion with friction occurs, another important consequence of many types of friction can be wear, which may lead to performance degradation and/or damage to components. Friction is a component of the science of tribology, Friction is not itself a fundamental force. Dry friction arises from a combination of adhesion, surface roughness, surface deformation. The complexity of interactions makes the calculation of friction from first principles impractical and necessitates the use of empirical methods for analysis. Friction is a non-conservative force - work done against friction is path dependent, in the presence of friction, some energy is always lost in the form of heat. Thus mechanical energy is not conserved, the Greeks, including Aristotle and Pliny the Elder, were interested in the cause and mitigation of friction. They were aware of differences between static and kinetic friction with Themistius stating in 350 A. D. that it is easier to further the motion of a moving body than to move a body at rest.
The classic laws of sliding friction were discovered by Leonardo da Vinci in 1493, a pioneer in tribology and these laws were rediscovered by Guillaume Amontons in 1699. Amontons presented the nature of friction in terms of surface irregularities, the understanding of friction was further developed by Charles-Augustin de Coulomb. Coulomb further considered the influence of sliding velocity and humidity, the distinction between static and dynamic friction is made in Coulombs friction law, although this distinction was already drawn by Johann Andreas von Segner in 1758. Leslie was equally skeptical about the role of adhesion proposed by Desaguliers, in Leslies view, friction should be seen as a time-dependent process of flattening, pressing down asperities, which creates new obstacles in what were cavities before
A wing wall is a smaller wall attached or next to a larger wall or structure. In a bridge, the walls are adjacent to the abutments. They are generally constructed of the material as those of abutments. The wing walls can either be attached to the abutment or be independent of it, Wing walls are provided at both ends of the abutments to retain the earth filling of the approaches. Their design depends upon the nature of the embankment and does not depend upon the type or parts of the bridge. The soil and fill supporting the roadway and approach embankment are retained by the wing walls, the wing walls are generally constructed at the same time and of the same materials as the abutments. Wing walls can be classified according to their position in plan with respect to banks, the classification is as follows, Straight Wing walls, used for small bridges, on drains with low banks and for railway bridges in cities. Splayed Wing walls, used for bridges across rivers and they provide smooth entry and exit to the water.
Their top width is 0.5 m, face batter 1 in 12 and back batter 1 in 6, return Wing walls, used where banks are high and hard or firm. Their top width is 1.5 m and face is vertical, scour can be a problem for wing walls and abutments both, as the water in the stream erodes the supporting soil. Wing walls provide smooth entry of water into the site and provide support. Wing walls can serve as buttresses to support walls and they can be purely decorative
A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads or electricity and telecommunications signals, Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Wire gauges come in standard sizes, as expressed in terms of a gauge number. The term wire is used more loosely to refer to a bundle of such strands, as in multistranded wire. Wire comes in solid core, stranded, or braided forms, edge-wound coil springs, such as the Slinky toy, are made of special flattened wire. In some cases, strips cut from metal sheet were made into wire by pulling them through perforations in stone beads and this causes the strips to fold round on themselves to form thin tubes. This strip drawing technique was in use in Egypt by the 2nd Dynasty, from the middle of the 2nd millennium BCE most of the gold wires in jewellery are characterised by seam lines that follow a spiral path along the wire. Such twisted strips can be converted into solid round wires by rolling them between flat surfaces or the wire drawing method.
The strip twist wire manufacturing method was superseded by drawing in the ancient Old World sometime between about the 8th and 10th centuries AD, there is some evidence for the use of drawing further East prior to this period. Square and hexagonal wires were made using a swaging technique. In this method a metal rod was struck between grooved metal blocks, or between a punch and a grooved metal anvil. Swaging is of great antiquity, possibly dating to the beginning of the 2nd millennium BCE in Egypt and in the Bronze and Iron Ages in Europe for torcs, twisted square-section wires are a very common filigree decoration in early Etruscan jewelry. In about the middle of the 2nd millennium BCE, a new category of decorative tube was introduced which imitated a line of granules. True beaded wire, produced by mechanically distorting a round-section wire, appeared in the Eastern Mediterranean and Italy in the seventh century BCE, a forerunner to beaded wire may be the notched strips and wires which first occur from around 2000 BCE in Anatolia.
Wire was drawn in England from the medieval period, the wire was used to make wool cards and pins, manufactured goods whose import was prohibited by Edward IV in 1463. The first wire mill in Great Britain was established at Tintern in about 1568 by the founders of the Company of Mineral and Battery Works, apart from their second wire mill at nearby Whitebrook, there were no other wire mills before the second half of the 17th century. Despite the existence of mills, the drawing of wire down to fine sizes continued to be done manually. Wire is usually drawn of cylindrical form, but it may be made of any desired section by varying the outline of the holes in the draw-plate through which it is passed in the process of manufacture
A beam is a structural element that primarily resists loads applied laterally to the beams axis. Its mode of deflection is primarily by bending, the loads applied to the beam result in reaction forces at the beams support points. The total effect of all the acting on the beam is to produce shear forces and bending moments within the beam. Beams are characterized by their manner of support, length, historically beams were squared timbers but are metal, stone, or combinations of wood and metal such as a flitch beam. Beams generally carry vertical gravitational forces but can be used to carry horizontal loads, the loads carried by a beam are transferred to columns, walls, or girders, which transfer the force to adjacent structural compression members. In light frame construction joists may rest on beams, in carpentry a beam is called a plate as in a sill plate or wall plate, beam as in a summer beam or dragon beam. In engineering, beams are of types, Simply supported - a beam supported on the ends which are free to rotate and have no moment resistance.
Fixed - a beam supported on both ends and restrained from rotation, over hanging - a simple beam extending beyond its support on one end. Double overhanging - a simple beam with both ends extending beyond its supports on both ends, continuous - a beam extending over more than two supports. Cantilever - a projecting beam fixed only at one end, trussed - a beam strengthened by adding a cable or rod to form a truss. In the beam equation I is used to represent the moment of area. It is commonly known as the moment of inertia, and is the sum, about the axis, of dA*r^2, where r is the distance from the neutral axis. Therefore, it not just how much area the beam section has overall. The greater I is, the stiffer the beam in bending, beams experience compressive and shear stresses as a result of the loads applied to them. Above the supports, the beam is exposed to shear stress, there are some reinforced concrete beams in which the concrete is entirely in compression with tensile forces taken by steel tendons.
These beams are known as prestressed concrete beams, and are fabricated to produce a more than the expected tension under loading conditions. High strength steel tendons are stretched while the beam is cast over them, when the concrete has cured, the tendons are slowly released and the beam is immediately under eccentric axial loads. This eccentric loading creates a moment, and, in turn
Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward one another, including planets and galaxies. Since energy and mass are equivalent, all forms of energy, including light, on Earth, gravity gives weight to physical objects and causes the ocean tides. Gravity has a range, although its effects become increasingly weaker on farther objects. The most extreme example of this curvature of spacetime is a hole, from which nothing can escape once past its event horizon. More gravity results in time dilation, where time lapses more slowly at a lower gravitational potential. Gravity is the weakest of the four fundamental interactions of nature, the gravitational attraction is approximately 1038 times weaker than the strong force,1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, gravity has an influence on the behavior of subatomic particles. On the other hand, gravity is the dominant interaction at the macroscopic scale, for this reason, in part, pursuit of a theory of everything, the merging of the general theory of relativity and quantum mechanics into quantum gravity, has become an area of research.
While the modern European thinkers are credited with development of gravitational theory, some of the earliest descriptions came from early mathematician-astronomers, such as Aryabhata, who had identified the force of gravity to explain why objects do not fall out when the Earth rotates. Later, the works of Brahmagupta referred to the presence of force, described it as an attractive force. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and this was a major departure from Aristotles belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere, galileos work set the stage for the formulation of Newtons theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newtons theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets.
Calculations by both John Couch Adams and Urbain Le Verrier predicted the position of the planet. A discrepancy in Mercurys orbit pointed out flaws in Newtons theory, the issue was resolved in 1915 by Albert Einsteins new theory of general relativity, which accounted for the small discrepancy in Mercurys orbit. The simplest way to test the equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the rate when other forces are negligible