TYPES of BARRIERS

Post 570 by Gautam Shah

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Barriers are obstructing and intervening entities. Barriers through their configuration, position and occurrence affect things passing by, touching, or going through them. Barriers rarely operate on their own, so are distinguished by the context or the surroundings where they operate. Barriers operate as multi functional entity doing many intended and unintended things.

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Wikipedia image by Elelco72

Physical barriers are omnipresent in structure and effect. But non-physical barriers could occur through sensory variations. A subtle shift in texture, gradient, colour, illumination level, view, temperature, audio perception changes the behaviour of the user and can become an effective barrier.

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Visual barricades use colours in terms of their brightness and other optical qualities such as fluorescence, reflection and background-foreground contrasting. Visual barricades also include use of illumination or brightness, blinking (dynamic) lights, iridescence. Some of the most important virtual barricades are communication jammers and devices that open channels within jammed zones.

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Tactile paving in Subway at Nagoya Japan, Wikipedia image > Attribution LERK

Barricades Consuming Energy bar or control the exchange between the two faces. Barricades, themselves are variously affected by the exchange occurring through them. Some barricading systems use energy, to cause specific changes during the exchange process and also to revert to the nominal status. Barricading systems capable of using energy are machines, or some live beings, if additionally can reproduce or self sustain.

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Electrified barbed wire fencing at Nazi death camp Auschwitz, Poland > Wikipedia image by Pimke

Protective barricades are designed to resist the most unfavourable combination of imposed loads (impact, wind, etc.). Such barricades allow planned deflection and distortion, with or without a collapse. A noncollapsible barricade is resilient enough to revert to the original position, whereas the collapsible barricade at a predetermined stage becomes ineffective. These conditions are included through a structural configuration, material technologies and through machine devices (operating on feed forward and feed back).

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Soft Barricades recover after an impact, but do not bounce-back the striking object. Rubber flaps or plastic stripes on warehouses doors are flexible barriers.

Hard Barricades are used to divert (bounce back) the force of the impact. On express highways the shape and height of the railings and curbs are so designed that a vehicle on striking slides along it rather than thrown-back into the fast-moving traffic.

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Concrete barriers > Wikipedia image by Pushcreativity

Transparent, Translucent Or Opaque Barriers: A glass barricade could be transparent for light but not for other objects. A large aperture grill could be ‘transparent’ for light, air and view, ‘translucent’ for an infant, pet etc., but ‘opaque’ for a fat man. A vertical or horizontal Venetian blind could be ‘transparent’ or ‘translucent’ from a particular position and could be ‘opaque’ from another position. A smoke glass is ‘opaque’ for view from outside but ‘transparent’ for view from inside. Fast-moving air in an ‘air curtain system’ is a transparent barricade.

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Notional Barricades are used for ceremonial purposes or as a representative form of a barricade. A wrought iron chain, a rope around a monument, podium, dais or rostrum, a red ribbons for inauguration, yellow tape of police investigation teams, are all notional barricades. Similarly signs and symbols (danger, do not enter, slow, stop) can also be used for barricading. If the users are knowledgeable, and are ready to accept a set social behavioural norm, than indicative barricades (non physical) are as effective as physical barricades. However, it should be possible for the user to recognize, feel and experience the presence of such barricades. Where such opportunities for recognition are not available, non physical barricades fail to be effective. Notional barricades are not recognized in a crowded area or in a chaotic situation. Similarly where barricades are required as protection against unknown elements, notional barriers are not effective.

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Barricades are required at all places of hazards such as: construction sites (for the safety of workers, visitors, and trespassers), works in public areas (such as trenches, excavations), place near electrical equipments (with exposed parts that could be live, and installations with voltage of over 440 volts), any area where explosives are used or stored, to define the radius of any cranes or such equipments, etc. Barricades serve as warning (through visual and other sensorial recognition) and also as a protective element. Barricades also denote territories, ownership and right of ways.

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BARRIERS in BUILT SPACES

Post 535  by Gautam Shah

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Mies van der Rohe’s Barcelona Pavilion Wikipedia image by Marb~commonswiki

A built space is a conditioned entity. The conditioning of the space through various types of barriers endows unique spatial character. The spatial characteristics are environmental, sensorial and function or task oriented. The barriers are protective, directive, indicative, transitive and formative. Barriers protect by their configuration, position and occurrence affect all things passing by, touching, or going through them. Barriers by their body and shape redirect energies and energy laden (moving) objects. Barriers are physical presences and so indicate spaces and segments in it. and through the degree of transparency allow transitions. Barriers are formative, doing many intended and unintended effects. The effects are distinguished by the context or the surroundings where they operate.

Walls of Dubrovnik (Croatia) Wikipedia image by Author László Szalai (Beyond silence)

Barriers are obstructing and intervening entities in buildings and outside in nature. Barriers are effective as a surface and so changes distinctly different conditions on its sides. One must perceive ‘the non-change situation’ to recognize the change caused by the barrier. Barriers are often so extensive that the change or modified environment is not recognized. Barriers, as a result, are evident at the ends, edges, joints, thresholds, cut sections, or gaps. And as a result a built-form manifests at its openings. Barriers in built forms are conceived as an intervention to delay or condition the reach to other spaces.

Poulnabrone Dolmen, County Clare, Ireland wikipedia image by Author User Kglavin on en.wikipedia

Barriers condition the reach to the other spaces by their capacity to obstruct, absorb, filter, reflect or deflect not just energies and physical things but cause metaphysical variations. The metaphysical variates are indicative, unreal or make-believe. A society accepts certain words, signs metaphors, and indications as warnings, danger, caution, or permissible signs. Such indicatives in the form of taboos, beliefs, customs etc. derive from the accumulated experiences. Belief in God is one such indicative. The metaphysical variates are reinforced by their association to predictable effects. Certain spatial experiences are associated with specific forms, materials and environmental conditions. When one or few of these manifest, the barrier like effect takes place. Designers exploit such conditions to generate dramatic or melodramatic effects. The Make-believe occurs because we are conditioned by predictable responses of form sequencing, materials, textures, colour, illumination frequency and schedules of occurrence etc. Certain predictable effects, when fail to happen and a delusion occurs.

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Notional barriers are indicative ones used for ceremonial purposes. Other indicative barriers consist of signs and symbols, which are effective if the users acknowledge and confirm it as a social behavioural requirement. Notional barriers are not recognized in a crowded area or in a chaotic situation. Similarly, where barriers are required as protection against unknown elements, notional barriers are not effective. Physical barriers demarcate territories, ownership and right of ways, but notional indicatives like presence of a person, smoke coming out of chimney, foot-ways or foot-prints, ashes of fire, etc. are accepted as indications of human occupation and possession or sign of trespassing.

Nepal – Sagamartha Trek Stone house Wikipedia image by Author McKay Savage

Barriers need not be very extensive, persistent and with substantial change capacity to be effective. Some subtle conditions are good enough to effect the change. A small sensory variation such as shift in colour, texture, gradient, illumination, view, temperature, audio perception, can have profound behaviour changes, and are effective as barriers. The sensory variations are caused by spatial context, background-foreground contrasts, extent of field, exposure to the sensorial limbs, time delay or interlude, sequencing, etc.

Barriers consume energy to bar or control the exchange between its two faces. The barricading systems use energy to cause specific changes during the exchange process, and also to revert to the nominal status. These barriers are machines, or a live beings, if additionally can reproduce or self-sustain. Barriers absorb the forces like impacts and generate energy, ultimately dissipated to environment, or consumed for productive purpose.

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GUARDRAILS

GUARDRAILS

Post 388 ⇒   by Gautam Shah 

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Guardrails are, both, protective barriers and rails for guidance. These are placed against a drop in terrain (of more than 750mm), against the edges of exclusive passage, or rights of ways. Guardrails, mark a visually recognizable guide line. Such guide lines are recognizable in inclement weather (heavy rains, fog, smog and darkness). A guard rail often is designed to bear heavier impact of side thrusts in comparison to a hand rail. A hand rail, as per most of the building standards cannot have a gap larger than 100 mm, whereas for Guardrails can have a gap slightly smaller than the front wheel dia of the vehicles, or at least 220mm.

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Interstate Highway through Colorado > Wikipedia image by Retaildesigner

 Guardrails are placed in buildings, terrains and roads. Many of the edge side structures such as, hand rails, parapets or fences can be called guard rails. Guardrails are both man-made structures or contoured natural features. Guardrails on any type of passage ways should be minimal. Modern roads are designed in a manner to eliminate the need for a guard rail. These means include provisions of apron spaces, contoured ends and landscaped features to indicate presence of zones of dangers. Road barricades work as guardrails. Many are installed as temporary (demountable) or permanent structures to prevent surprise or forced entry of terrorists or demonstrators.

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Kaluga region Trassa Road side barricade > Wikipedia image by Denghu at English Wikipedia

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Jeresy type barriers against car attacks in Israel  >Wikipedia image by Netanel h

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Protective Road Guardrails or barricades -folding and lightweight by Police > Flickr image by Indi Samarajiva

 

Guardrails are essentially of two types: 1. Rigid ones bear an impact to an extent, but mainly help bounce back of the object in certain direction, and possibly retard the movement of the object; 2. Flexible ones bear the impact substantially within the body and yet redirect the object to a safer zone. In both the cases an objective is to keep the vehicle upright while being deflected along the guardrail.

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Lantau Island Sunny Bay Road HK > Wikipedia image by Summa06

 Road guardrails are designed with the roads or installed as retrofit when certain sections show such a need. Former types of guardrails are fairly long whereas the later types are zone-specific and comparatively shorter. Specific types of guide rails are placed to prevent accidents due to the road elements or fixed objects. These elements include bridge supports, piers, road signages, culverts, trees, etc.

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Live Guards forming a Rail for crowd control > Wikipedia image by Craig Martell

 Guardrails on roads and other sites have the inner edge (use or the movement side face) completely free of obstructions. The rails are so constructed that they form a continuous visual and functional surface. The joints formed with a backing element rather than by lapping. The colour and surface texture are consistent.

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Crowd anti stampede Guards at Saltergate > Wikipedia image by Jaxban 

 Guardrails function as an integrated system where the guardrail, posts, post foundation structure and support braces, all share the impact load. In spite of a rigid design, guardrails do deflect. The amount of deflection depends on such factors as: straight or curved formation of the guardrail layout, height of the guardrail, shape or section of the rail, direction of the impact (parallel, head-on, angular), weight of impacting objects (mass-inertia), height of the impacting object, nature of support posts, and distance between the supports.

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Guardrails for Niagara Falls > Wikipedia image by Wladyslaw

Road and other guard rails are universal structures, serving variety of vehicles (cars, trucks, motorcycles, cycles), people (adults, infirm, children, rowdy crowds), climatic conditions (rains, fog, smog, snow), and varying terrain conditions (floods, landslides, dumping, oil leaks). An optimum height for a car may not prevent a truck from toppling over the rail and a motorbike or human being sliding under it.

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Barricade Bollards > Pixabay free images by serghei_topor Enter a caption

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RAILINGS AND PARAPETS

RAILINGS AND PARAPETS

Post 303⇒   by Gautam Shah  →

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Railings and Parapets are barricades against height related hazards. Railings and parapets both are important functional and architectonic elements. There are few characteristics and elements common to both. It is their nature of construction that places them in separate categories. Both are height-related hazards barriers, mainly for humans. Railings and parapets are invariably smaller than the human height, because most such elements are used for resting or grabbing with hands. For nominal usage 800-900 mm height is adequate, whereas difficult to negotiate (jump-over) conditions a height of 1400-1500 mm is considered. The later height is used for terraces of multi-story buildings to discourage suicides.

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Design Parameters > Railings of nominal height ( 800-900mm) must have top 300mm as see-through face, so that children can see out. But if such a separation is likely to provide any toe space to climb up entire face should be see-through. All lattices should have preferably vertical bars and the clear gap must not exceed 100mm. For very tall railings (more than 900 mm) entire face must be of see-through elements and with a squared lattice. The squares in the lattice must not exceed 30 x 30 mm.

Parapets and Railings have sub elements such as: hand rail, Baluster or balustrade, banisters, volute, turn out, goose-neck, rosettes, easing, starting easing, over easing, core rail, newels, fillets, tandem caps, colonnettes.

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RAILINGS

Railings are translucent or latticed elements, placed at the edges of the floor and terraces. Railings are placed as safety barricade on the sides of stairs, ladders, ramps, and escalators. These are placed to demarcate zones, to segregate movement channels, to regulate queuing people, as barricade for animals, and to prevent crawling infants and children from moving into unprotected areas. Railings are placed near wells, tanks and other water bodies. Railings are placed on inclined or slippery floors to prevent slip-fall. Railings are placed in vast grounds for people or groups to anchor themselves.

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Waverley Tram Depot Roof gable edge

The chief element of railings, are top rail, and secondary elements are posts that support the rail and latticed in-fill panels. A rail can be defined as any long member, usually of round section, fixed to posts, for resting hands, or for grabbing as a support. Railings have a top rail or hand rail used for holding, and a foot rail and mid rails. The hand rail in a masonry structure is a wider ‘table’.

Balusters

Masonry railings are often called parapets. In medieval castles, gapped parapets called crenellations or embrasures were formed to allow guns to fire through. On terraces and galleries of arid climates similar gaps are covered by pierced stones or metal lattice to allow the breeze to pass through at floor level of the terrace. This cooled the terraces faster, and provided comfort for occupants seating or sleeping on the floor. Latticed railing allows children to see through, and so discourage the climb-over.

Poole: wiggly barrier on the Twin Sails Bridge UK

PARAPETS

Parapets are opaque structures, often designed as an upward extension of the wall. Classical design of a parapet em-battlement of a coping at the top and corbel below. The top of the parapet often slopes towards the enemy to enable the defenders to shoot downwards, and this incline is called the superior talus. Parapets are placed at roof or terrace edges, or on embankments. Opaque parapets are used for deflecting winds, provide privacy to floor level activities, add weight to the edge to prevent lift-off forces. Parapets serve, besides defence-offence, other purposes, such as: to shield a view, as a noise barrier, barriers against splashes of storm-water, missiles or flying objects. Edge beams are designed as parapets. Parapets that are small in size are called curbs. Curbs are used as dividers.

Glass Parapet >Nottingham Castle Terrace

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Fort walls have em-battlement parapets, which are pierced for styling, view beyond and for throwing defensive projectiles. Palaces and castles have decorative (non-defence) perforated parapets in various shapes such as circles, trefoils, quarter-foils.

The building act of 1707 in London and other towns of England banned the projected wooden eaves to prevent spread of fire along the wall, to the roof structure. A 18″ thick parapet was required and the roof edge was set back. The roof was set back little more to provide drainage of rain water. The parapet which was completely absent in earlier houses began to be treated by crenellation. (During medieval ages, provision of crenels required permission.) The parapet style was continued in Georgian houses giving an appearance of a flat edge roof. The parapets over the roofs were made taller, shaped, decorated and pierced.

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WALLS and Buildings

Post 244 – by Gautam Shah

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A wall is a planner structure, generally vertical, with a proportionately narrow thickness in comparison to its height and length. It is a barrier system, like fences, barricades, partitions, etc, and used for dividing or enclosing a space. Its most distinguishing function has to bear the load. It bears its own weight -the self load, and also other imposed loads of the super structures or sideways thrusts. Walls ultimately transfer all the loads, own and imposed loads or thrusts to the earth. One of the most efficient load transfer systems to the earth is in perpendicular direction to the gravity. As a result, in all structure compositions, the vertical walls predominate.

Walls of Stairs Kolkata India

Allen Lambert Galleria Toronto an atriumspace by Santiago Calatrava that connects several heritage buildings along the side of it Wikipedia Image by Secondarywaltz

Imposed loads on walls emanate from other structural systems of the buildings, such as floors and roofs, beams, services, etc. and from the occupancy of these systems, like ‘live’ loads of people, flora, fauna, goods, storage utilities. Thrusts from within the structures are transferred by the walls to other bearing elements, or resisted and converted into a gravity bearing vertical component. These loads include from arches, beams, vaults, etc. Thrusts also bear upon the wall due to the lateral resistance provided to other elements such as water, grains, sand, soil, etc. and retained liquids or gases. Walls also endure pressures arising due to dynamic movements of live loads and shifting dead loads, earthquakes, and energy vibrations of sound, wind, etc.

metal-glass facadesWalls carry distributed loads, but frequently loads concentrated at a point induce local stresses and failures. Walls also fail, under excessive distributed loads, at its weakest section, get crushed or deformed depending on its homogeneity. When a wall has width equal to or less than its length, it becomes a column, and loses its meaning. Moreover, a wall that has a height equal or less than its width, remains an in-fill course or a layer only. Walls without any external down bearing imposed loads are called partition walls.

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A wall carrying only side-thrust is called a retaining wall. A wall which carries the load of upper structure and also retains earth is an abutment wall. A gravity wall resists the side thrust of retained material by its dead weight. Gravity walls primarily have a trapezoidal section, with wider part forming the base. Cantilever retaining walls have ‘L’ or inverted ‘T’ section. A buttressed wall has additional intermittent pieces of lateral walls on the open face, to strengthen the mass. A counter-fort wall has a similar system (often as a structure in tension) on the inside or the loading face.

Wall Hazara Rama temple Hampi, Karnataka India Wikipedia Image by Ms Sarah Welch

Tabo Gompa - old walls and chortens Wikipedia Image by John Hill

Retaining Walls

Walls as barriers resist variety of forces or energies. A translucent to opaque wall can reduce light transmission. A wall of an absorbent material and geometric configuration is used in attuning sounds. Latticed walls as barriers filter out select elements. Small height walls are used as compound or estate walls and as parapets. Dispersed vertical linear elements used as non-continuous barricade function like walls. Curtain walls are rigid membranes that envelopes a building to protect it from winds and rains and many instances bear the surface shears.

Wall of Porta San Giovanni Wikipedia image by

Edward Durell Stone US Embassy Delhi Latticed wall

Walls are ‘loaded’ along and across the width section, and sometimes along the length-section. To bear a load, a wall is expected to have adequate surface cross sectional area in a plane parallel to the gravity. These surface component are made of width and length of the wall. Theoretically, a wall can have an infinite length and single size module of width. Nominal walls however, are required to bear a variety of loads, thrusts and stresses. So walls need some sectional depth, depending on the integrity or homogeneity and strength of its materials, in addition to the geometric formation and composition. Height of a wall is a finite element, though theoretically a wall could be infinitely tall. A tall wall, proportionally, turns into a slender structural entity. Wind and other vibrations over the surface of a tall or slender wall are random (stochastic) motions. These cause dynamic effects in many different directions. So even if depth (thickness) of the wall due to high integrity of material, composition or geometry, can bear the loads, the transmission of loads to the ground is not harmonic or consistent.

Walls of Red Fort Delhi India

Walls of Hyderabad (Pakistan) Fort -Pacco Qillo Wikipedia Image by MUrad Ali Shah Bukerai

Very thin walls are used in shells, domes, tanks, plates and membrane structures such as balloons. These are often called shell or membrane structures depending on their structural transmission. These structures often have indistinguishable wall and roof elements. A shell structure is classed as compressive structure, whereas a membrane structure like a balloon is classified as tensile structure. Thin structures are used for their light weight and economy. Membranes are thin and pliable materials or formed by ‘bloating’ or stretching a material along its plane. Membranes ‘wall’ or surfaces can carry well-distributed loads, but are incapable of taking any pointed loads, unless material is tear or puncture resistant. Boat sails and circus tents are examples of membrane structures. When a hard, homogeneous and rigid material is used for creating a thin wall structure it is called a plate or shell structure.

Walls of wonky brick building crooked old masonry house

Walls of Cooling tower at Thermal poer station Neyveli, Tamil Nadua India Wikipedia Image by NLC India Ltd.

Sail Ship -a membrane wall

 Walls of space vehicles and stations in outer space have few superimposed loads on the walls (once far beyond the nominal gravitational zone) however, if gets converted into stresses. The stresses ultimately result into some form of kinetic energy disturbing the equilibrium of the craft or station. To maintain the equilibrium (position and location), occasionally course-correcting boosters are fired.

Coventry Cathedral Ruins Flickr ImageOpenings like doors and windows, and provisions like niches, alcoves, weaken a wall. For reasons of load-bearing capacity of a structure, openings at lower level must be fewer of smaller width. Lower sections of structures, however, have lesser solar exposure, so more openings are required. Openings are placed one above the other so as to leave uninterrupted vertical wall masses to transfer loads directly to the ground.

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ENVIRONMENTAL BARRICADES

 

Post -by Gautam Shah

Environment is a complex system. Its various aspects affect us differently. Some effects are concurrent and few are directional. Environmental barriers serving many different purposes are required.

Noise barrier Geluidscherm_OverschieWIND BARRICADES

Wind barricades are used for heavy wind sections as well as for the storm prone locations, such as sea fronts, valleys etc. These are designed to deflect the direction and diffuse the velocity of the winds. The barricades primarily depend on the quality of the terrain and man-made formations, such as sand dues, walls, screens, vegetation, walls etc. Projections like galleries, Chhajjas, screens, are also used for diverting the winds to the buildings. The flow is also diverted to specific interior areas of rooms by wind catcher ducts. Tropical houses have terrace parapets with a grill or lattice design to let the air pass through. Louvered doors and windows also control the air movement.

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WATER BARRICADES

Water barricades are required against sea tides and ebbs, tsunamis, flooding, land washouts, snow and rain storms and eddy currents. These are in the form of vegetation, walls, dumps of modular or irregularly shaped cast units, landscaping and terrain contouring. Holland has devised variety of technological means against ingress of sea waters.

Sea front barricades of Concrete blocks against land erosion

SUN SHADING BARRICADES

Sun shading barricades are shading devices, usually vertical or horizontal, and often in inclined positions. Locations above 23° N or South of the equator receive no sun rays from respectively North and South faces. All location under (within) 23° N or S of equator, however, receive some sun rays, and to curtail it sun shading devices of horizontal flat or inclined shape are required. For the same locations, on East and West faces, early part of morning and later part of the afternoons receive horizontal rays, but with Southern inclination. These require a dual shading consisting of horizontal and vertical (on the South side of the opening) elements. Sun shading devices such as Brise de soleil are used.

Solar baffles

RADIATION BARRICADES

Radiation barricades are used against radiation sources, such as furnaces, open fires, oil wells and oil storage tank yards. Such barricades could be natural or man made. Natural radiation barricades are in the form of hills, contours, dunes, slopes, trees, hedges, foliage, plants, grass, climbers etc. Man-made radiation barricades are protection walls, embankments, ramparts, retaining walls and dykes.

Jet Blast Barricade

NOISE CONTROL BARRICADES

These are created against super highways, railway tracks, airport runways, open mines, stone crushing plants and sites with pile drivers. The noise control barricades are made of dense vegetation, fibre boxes (grass), and hollowed or staggered construction. Stage podiums have parabolic overhangs to direct sound away from the stage and thus avoid the feedback in sound amplification system. Telephone booths in public spaces like malls, road sides, railway stations have specifically designed envelopes to prevent the background noise. Cinema and performance auditoriums are designed with optimum 1/4 to 1/3 audience occupation, as the bodies of audiences and their clothing absorb sound. Noise control barricades are in form of contoured planes to deflect and amplify the sound, low density surfaces treatments, baffles or cavities to absorb select frequencies of sound, or frequency generators to produce sound attenuation.

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