MEASURING UP

Post 394 – by Gautam Shah 

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We define objects and happenings primarily with measures. Measures when combined with time show the changes that occur in things. Measures are very important in recording and recreating events and happenings, through their start, duration, termination, and the rate at which these actualize.

Roman Weight of stone

Measures define things in terms of lengths, areas, volumes or weights. Measures offer comparative scaling for sensorial perceptions, define load and work capacities, and determine reach and occupancy in space.

Human body limb sizes, reach and capacities -Basis of early measure systems

There was a time, when things were measured in terms of body sizes and capacities. Long distances were measured for the travel time required, like in lunch breaks or night halts. Short distances were measured in arm lengths, cubit (the length from the elbow to the tip of the middle finger), or foot steps of the traveller. Still smaller sizes were measured with the palm, breadth of a hand, length of a finger, or width of a thumb. Finer widths were measured in terms barley grains. Volumetric measures were the holding capacity of a limb like pinch or palm. Weights were measured in grains, fruits or stone pebbles, or in terms of carrying or displacement capacity of a person or animal, such as head load, a cart load, horsepower.

A common unit of weight in Ethiopia was the load – a simple measure of the amount carried by a beast of burden such as a camel

Measures are comparative facts. A thing to be measured is compared (equated) with something similar, familiar, or with a thing that has already been calibrated. Measures based on body sizes or capacities had many individual, racial and regional variations. Other standards were changeable and perishable. These units of measures were not replicable (recreate-able) and comparable. There was no hierarchical relationship between large and small measures. The conversion from one unit size to another was, often very illogical.

During the Middle Ages, major cities had their own set of measures and the public availability of these standards allowed visiting merchants to comply with local regulations. The official Viennese ell length standards for verifying the measure of different types of cloth sold are embedded in the cathedral wall, to the left of the main entrance. The linen ell, also called Viennese yard, (89.6 centimeters (35.3 in)) and the drapery ell (77.6 centimeters (30.6 in)) length standards consist of two iron bars.

The differences were somehow equated in barter trading between neighbours. But the same process was proving to be very difficult for trade with far of regions and transacted in some form of monetary units. There was an acute need for some common measure system. Gradually each trading block concurred to a common tradition of nominal measurements. Many different localized or regional measure systems flourished. Conversion between adjunct systems was not very difficult, as the trade occurred comparatively in small lots. Conversion of measures with adjoining trade regions was managed by intermediaries like brokers, caravan masters and shippers. The inconsistencies of the measure conversions were partly solved with monetary pricing replacing the bartered trading. The monetary trade system came to replace the barter trading, where only ‘universally’ measured goods were evaluated in a primary standard like gold.

Caravan Traders exchanging goods

At places things were transformed to different measure systems. Like grains were measured by volume (bushel) than by weight. Textiles were traded by weight than by lengths. Liquids (oils) were sold by volume. Yet, measure systems were mutually incompatible. To compound the problem each system had a different scale of sub fractioning. The complexity multiplied when differently fractionated measure units were equated with equally varied units and sub fractions of monetary units.

Measurement of mass – the gravitational force on the measure and is balanced against the gravitational force on the weights.

This problem of differential fractioning of measures and money was sought to be solved during the French Revolution. During the French Revolution (1870), the National Assembly of France asked French Academy of Sciences to formulate a scientific and rational measure system. Such a system was expected to be:

1 neutral and universal,

2 replicable anytime and anywhere,

3 to have decimal multiples,

4 to follow common prefixes,

5 be practical and simple to use.

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BEVELLED GLASS in DOORS and WINDOWS

Post 393 – by Gautam Shah 

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geograph-3797493-by-J.Hannan-Briggs

A bevelled glass is made by dressing or grinding the edge or sections of a design with a slope, chamfering or an angled edge to create special effects. The edge dressing creates a prism like effect and alters the way light refracts while passes through the glass or reflect of the surface. Bevelling splits the light into unusual patterns including a rainbow of colours. Bevelled glass is installed in doors and windows to add dynamism to daylight illumination of a room. There were few other techniques of treating the glass, like fire finish, etc. for special lighting effects. These were devised as soon as glass for windows matured in quality.

Green Roman glass cup unearthed at Eastern Han Dynasty (25-220 AD) tomb, Guangxi, China

Early glass, such as of Romans was mainly in the form of fuzzy disks that were inserted in terraces, arched barrels and domed roofs for illumination of interiors. These were very fuzzy or low intensity illuminating devices. Glass disks were polished to reduce the fuzziness due to the surface or casting related impurities. Irregularities related to manufacturing were of several types, such as the colourant contamination, bubbles or casting -moulding methods. In spite of grinding, all of these could not be eliminated so easily. Clear glass panes of some translucency were first made by blowing it to thin walled cylinders or bulbs, then cut and flattened. These, 3rd C, methods gave clearer glass, because it was of a thinner body and larger in size than the cast disks. These panes were placed in structured punctures as a fixed panels. The glass was more translucent but visually very hazy.

KONICA MINOLTA DIGITAL CAMERA

The hazy glasses, however, provided wonderful glow to interiors. The costs were prohibitive due to the rarity, high cast of installation and need for frequent replacement. The ‘daytime glowing glass’ had inconsistent levels of impurities. An opening with several such panes would look fairly patchy, but this was camouflaged with glass colourants. The colourants or staining compounds offered a palette of colours.

The stained glass provided a daytime glow to the interiors, but it was not a working level of illumination. The increased openings’ size and larger glazed extent provided sufficient interior illumination on clear day and for few hours of daytime exposure. This problem was solved by using lighter tones of colours than the ‘pot’ glass, and by leaving substantial sections of image backgrounds (other than the holy images) of colourless glass.

Typical fuzzy glass in the 14th century Lyme Regis watermill, UK.

The Church interiors began to use glasses of lighter colours and plain glasses. These reduced the overpowering effect of colour in the interior space, allowing gilding and other ornamental details to be seen and also permitting the building to glow on outside, at night with interior lighting. It also allowed the reappearance of wall paintings, and colouring of architectonic interior elements.

Elegant figures in subdued colours. 1890

The glass as produced by cylinder or crown method was hazy, with marks of flutes but fairly colourless. It was of small sized panes. The panes were joined together with lead cames. The lead cames which earlier, marked the free flowing strong defining lines of the image, were now grid forms. American colonial sash windows represent the classic grid. The glass, of the industrial revolution period had manufacturing defects such as lines, flutes and rings. It was not possible to view the exterior as one large picture across the leads. The leads’ grid however imposed a visual discipline, rest of the disguising was achieved by thin see-through curtains and by painting the windows white.

Stenciled quarries of cathedral glass, c. 1900

During the industrial revolution period clear quality glasses of very large sizes began to be available. Very large and absolutely flawless, water white clear glass had its own problems of acceptance. It was too clear for the interior privacy, and provided no framing or visual masking over the view to outside. The problem was partly solved by installing curtains with both sides having visual appeal. Its appearance was rather too consistent.

Bluecoat Chambers in Liverpool, 1717

Some longed for the dynamism of variegated glass and visual masking. These two elements were provided by engraving and etching the glass surface with textures and patterns. To this was added the technique of glass bevelling. Glass bevelling is done in THREE basic manners. Edges of the glass panes are bevelled, very much like the wood panels in a door. Glasses are bevelled grooved by engraving. And the glasses are overlayed by smaller pieces of bevelled edged shapes.

St Nicholas Church Moreton Dorset

Bevelled glasses are used for doors, windows and partition panels. The bevelled glass is often additionally treated with grinding, etching, engraving, and painted staining work. Bevelled glass was favoured as it provided occlusion for privacy and isolation, but nowadays window glasses with various levels of tinting, metallic sprays, polyester films, etc. provide the same facility. Bevelled glass is still unrivalled in terms refracting the light in a spectrum of colours and dynamism.

Engraving on Glass

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NATURE OF OPENINGS

NATURE OF OPENINGS

Post 392 ⇒   by Gautam Shah 

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An opening is any space or gap within a barrier. An opening is meaningful so far it is in a barrier. The opening could be a ‘puncture’, surrounded by the barrier on all its sides, or a cleavage between two barriers. Openings are also called ports, as across the opening one can ‘board’ a new system. An opening is called a passageway, as this is the only way, one can, transit a territory.

Chaco Canyon Pueblo Bonito doorways

An opening can never be larger or equal to a barrier within which it resides. All physical openings have a finite size. A smaller opening makes a barrier system very evident, whereas a large opening or multiple openings make barriers less effective. Opening systems are also ineffective in transparent, translucent or frequently interrupted (broken or discontinuous) barriers. A room with a lattice wall all around has no need for a window, or a glass cabin has no need for an opaque (solid) door.

Manhattan Bridge Arch and Colonnade

Openings are defined by superlative structures to denote the presence and control the activities occurring through it. The superlative structures over passageways such as Gates, Gateways or Doorways are large in size and very distinctively formed. Formal structures have shutter devices whereas symbolic structures are simple openings. Nominally a passage is a linear entity, and so do the gates have singular passage. Cross junctions of passages require four or more sided gates.

Multiple Openings

The superlative structures function as control Gateways over openings. Such openings’ control the transactions, by way of the size, volume, temporal rate of passage and the qualitative nature of things. The transactions across the openings are of two ways, exit and entry types, and so the controls are also dualistic.

Gates with sensors

Gates with minimal structure

All communication channels have Gateways, from where the traffic gets diverted to appropriate channels and portals where divergent traffic gets ‘routed. These gateways register size of individual transactions, time of arrival-departure and source-destination of traffic. But most importantly there are ‘protocols’ that check whether the destined item has reached or not.

Surveillance gates or ports

In buildings openings like Gates, Doors, Windows, Ventilators, Gaps, Cracks, Crevices and Punctures all denote physical entities, but there are innumerable imperceptible points where observance and control occur. The sensors, cameras, readers, etc., are concealed, made minute in size and programmed so that ‘Gates’ structures are not imminent.

Openings in buildings have facilities for allowing sunlight, air, sounds and for framing view of the outside. The openings also create architectural patterns, compositions through scaling and proportioning, endow specific style character, affinities and identities. The openings occur in a barrier system as a connecting threshold or edge between two distinct worlds, but their own presence assumes many different guises. An opening is designed to be a distinct medium investing a nature of relationship between spatial domains.

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FUSION JOINING SYSTEMS

FUSION JOINING SYSTEMS

Post 391 ⇒   by Gautam Shah 

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Fusion welding is a common term to describe a process of joining by melting or softening with heat, energy or chemical action, two similar or dissimilar materials.

Fusion joining systems are used in fabrication of metals and thermoplastics. There are basically THREE categories of fusion joining systems. For soldering and brazing, the work pieces are not melted, yet joined by using a melt-able filler material. For welding the work pieces, and in some instances, the filler material, both are melted. The joint is created with or without application of pressure. Some plastics are joined by solvents that dissolve (soften) the surface areas of the work pieces; this is often termed as a solvent welding, but this is truly an adhesion fixing.

Forged wrought Iron joints

Fusion joining requires a heat source, such as a gas flame, an electric arc, a laser, an electron beam, friction, or ultrasound. Fusion joining sometimes requires a slight to very heavy pressure. Fusion joining is done under many different environmental conditions like open air, rain, frost, underwater in vacuum or space and sometimes under the shield of inert gases like Nitrogen, Argon, Helium, Carbon dioxide, etc. Fusion joining in spite of all care is essentially a hazardous procedure. It involves risks of high electric currents, high temperatures, sparks, fumes, and radiation.

Powder welding joint

Forge welding was the first fusion joining process. Blacksmiths used to beat the heated and overlapped metals for joining. Wood, charcoal and later mineral coals were used to heat the work pieces.

Soldering and Brazing use external metal softening at low temperature. For the purpose gold, silver, tin, lead, were common in craft work.

During 1800s, DC power sparking, Oxygen-fuel, and arc processes were developed for fusion welding processes, The results were unreliable as joints cracked and came of the surfaces. It was in the 20th C that AC power was consistently produced and distributed. After world war II, Plasma, laser and electron welding systems, along with X-ray technology for checking the integrity of welded joints were developed. Deep and narrow welding became possible with concentrated heat of Electron beam welding (1958). Later in the 1960s the laser beam welding helped high speed clean profile cutting and automated precision welding. Though both processes are expensive are used for special applications. Today industrial plants have the robotic welding systems, using these technologies.

Friction welding uses heat generated through friction and then pressure to achieve joining. Friction heating is generated by sliding the parts together, and as the surfaces soften, heavier pressure is applied.

Oxy-fuel welding is one of the best-known forms of fusion welding. This uses fuel gases, like acetylene, liquid petroleum, hydrogen, propane, natural gas or propylene with oxygen. Typically Acetylene gas and pure oxygen can generate flame temperatures of 3500 C. This flame is hot enough to melt most industrial metals.

Gas arc Welding

Gas arc Welding

Arc-welding uses electricity to generate an electric arc between an electrode and the pieces of metal to be joined. It is homogeneous welding. It is most widely used method of welding.

Electric resistance welding is similar to the arc-welding. In this process two electrodes are placed on either side but close to the piece to be welded. As the electrodes are brought closer under pressure to create resistance and thereby heat. One of the known such process is butt or spot welding.

Thermit welding is uses intense heat generated by igniting iron oxide and aluminum powder. This process is used for joining rails at remote sites where heavy equipment cannot be carried.

Tram Rail joining by thermit welding

Laser beam welding uses very precise heat source of a laser. The lasers penetrate deep and narrow areas without affecting the surrounding parts. It requires heavy industrial set-up.

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Heat fusion processes are good for heat fusible substances like metals and some plastics, but induce stresses in the mass. Electric resistance processes of welding require electrically conductive mass. In fusion joining processes the deposited substances are heat-hardened and these are very difficult to grind out. Joint testing procedures such as X-ray and sonography are elaborate and not always perfect.

Welding roads with flux coating

Fusion joining systems require power or energy input, a filler material, a flux and often a shield gas. Welding in certain situations are done without the use of a filler material. Filler materials where used, are invariably of compatible materials in terms of melting point temperature, alloying capacity, fluxing capacity. These are in the form of powders of pure metals, alloys, oxides and such other compounds, ceramics, granules, foils, wires, and rods. Flux or fluxing agents are required to dissolve the existing, and to be formed oxide. Welding rods are coated with borax and aluminum chloride. Stainless steel welding requires zinc chloride and hydrochloric acid in equal parts. Soldering of the Galvanized surfaces need hydrochloric acid. Brass soldering requires tallow or rosin. Soldering of tinned surfaces require hydrochloric acid or rosin. Copper, Brass and gun metal need aluminium chloride, hydrochloric acid or ammonium phosphate. Shield gases are inert or noble gases (constituting O group of a periodic table), such as Helium, Neon, Argon, Crypton, Xenon, Radon. These gases do not react with other materials so are used for forming an environment so that outside contaminants and other substances do not react with the weld. Some other non-inert gases are used for welding, are Carbon dioxide and Nitrogen.

Fusion Joining has few inherent issues. Distortion occurs due to substantial thermal expansion and contraction. Oxidation occurs at high temperatures, which prevents either joining or results in poor bonding. Oxidation can be prevented by welding in protected environments (metal inert gas -MIG, and tungsten inert gas TIG). In oxyacetylene welding, the gases produced by combustion prevent oxidation. In certain cases the electrodes are coated with a fluxing agent. Cracking occurs for many reasons such as inadequate heat and moisture in air. Stresses in the welded zone and surrounding areas (heat-affected zone -HAZ) occur due to high heat. Prolonged cooling anneals the steel.

This fusion joining can be also done for metal, ceramic and other polymer surfaces with use of alternating magnetic field to heat and melt a nano-crystalline iron-aluminum powder, which then cools to bind the surfaces of two parts.

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STITCHING AND SEWING

Post 390 ⇒   by Gautam Shah 

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Stitching is mainly done on fibre, film or pliable laminar assemblies. Stitching is a continuous linear fastening system, compared to Knotting, which is of intermittent stitches. Machine Stitching is common to garments and bags packing (cement, grains). Machine stitching is done with two individual fibres, on either of the faces, so a fibre pull from the other face (from the machine) may undo the assembly. Hand stitching is used for garments repair (Rafu – darning work in India) and for preparing Razais (Indian blankets stuffed with cotton). It is done with a single fibre as a continuous stitch, and so is more stable, but not necessarily stronger. Knotting is very common in making of cotton mattresses. It is stable and stronger as each knot is tied separately, and even if one of it comes apart, does not affect the entire assembly.

Different types Threads for Quality of Fabrics

Majority of stitches are made with a needle eyed at the end. Cobblers, sports goods manufacturers, and for heavy duty work a notched hook-needle is used to pull over a looped hung-thread. Complex stitches may employ one to four threads. There are several variations of stitch formations, such as, Running stitch, back stitch, looped stitch, edge seaming stitch, darning or Rafu work stitch, buttons hole stitch, etc.

Needles (for Hand sewing

Sewing awl

Stitching materials are threads of cotton, silk, rayons, polyester, Nylon (Aramid), stretched guts of animals like cats, spliced leather, metal wires and spliced stripes, (silver, gold, copper, aluminium). Stitching material must have strength equal or less than the material to be stitched. A stronger stitching thread cuts into the material being stitched.

Sewing Tools for Leather

Specific materials are used for joining two similar or dissimilar materials. Materials that are fragile (stitch cutting into the material), are stitched with extra resilient strips, on one or both faces.

Quilting stitches

Surgeons use stitch materials made of animal guts (processed intestines of cats stretched into a fine thread) or fine quality nylon, polyesters and Teflon. Surgical stitching material must not biologically react with body. Dissoluble and de-gradable threads are also used in surgical procedures.

Knotting in Mattresses > Wikipedia image by Jeffrey M. Vinocur

Fusible threads fuse to form a joint with the fabric, on post stitching heat or chemical treatment. Rafugars (Indian -fabric/garment darning) use very fine threads, or often single filament fibres to create a network of stitches (akin to weaving or knitting), to join torn sections and strengthen weakened areas. The filament is pulled out from the selvage of the fabric (or garment) to create a perfect colour match.

Glove Ball Baseball

Knotting is in many ways similar to stitching, but unlike the stitching it is not a continuous process. Knots are created intermittently or at the end of a ductile or flexible linear element like yarn, thread or a rope. Cross knots tie up an assembly, to join one linear unit to another, and Wraps keep unravelling loose ends of a thread or rope. Knotted wraps also do not let a rope or thread go-off, whereas Unknotted wraps are created by winding loose ends, or with the help of an extra thread or wire to form a smooth end that can easily slide through a whole, eyelet or sleeve.

Leather boot stitches

Elevator metal wire ropes’ ends are rolled over a circular section and secured together by a friction holder. Pre-stressed wires in RCC structures, wire rope bridges also use similar friction holders of conical shape.

Lashes are straps or stripes cut from of leather, polypropylene like plastics, or malleable metals, or knitted or braided threads of round or flat section. Lashes are used for tying sails, tents, shoes’ uppers, paper, bamboos, canes, etc. with or without the use of eyelets. Straps are secured by buckles, knots, rivets or wraps. Metal lashes or straps of annealed mild steel are used for tying bales of cotton and bundles of fabrics. The ends are tied together by crimping a small piece of malleable metal or by riveting. Fodder grass bundles are tied using metal wires. Here ends are secured by knotting.

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STAINLESS STEELS

STAINLESS STEELS

Post 389 ⇒   by Gautam Shah 

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Stainless steel is an alloy steel, with low carbon content but with 10 to 30% Chromium. Chromium provides resistance to corrosion. The presence of nickel adds to corrosion resistance in acid environments and fabrication characteristics. The presence of molybdenum improves corrosion resistance in sea water or chloride conditions. Other elements such as, titanium, aluminum, niobium, copper, nitrogen, sulfur, phosphorus, and selenium may be added to increase corrosion resistance in specific environments and impart special mechanical characteristics, such as, form-ability, weldability, machine-ability, strength, hardness, etc.

Lloyds Building UK stair-case

Chromium was first reduced from its ore in late 17th C, and by beginning of 20th C, it began to be used to form alloy with steel. The stain-less characteristic is achieved with chromium in greater than 10.5 %. The first stainless steels were straight iron-chromium alloys, which were used for production of cutlery.

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This article created for Interior Designers, avoiding complex terms and too many technical details. A lay person or non expert like Interior designer is required to decide about using stainless steel, few basic quarries arise. Is the SS completely rust proof? Is it a food grade material? Can it be cast?, Can it be rolled and formed without problems like fracture or cracking? Is it magnet-proof? Can it be welded and How? Can it be machined?

SS rail Car

Most stainless steels are first melted in electric-arc or basic oxygen furnaces and subsequently refined in another steel-making vessel, mainly to lower the carbon content. In the argon-oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. By varying the ratio of oxygen and argon, it is possible to remove carbon to controlled levels by oxidizing it to carbon monoxide without also oxidizing and losing expensive chromium.

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There are THREE major groups of stainless steels: Ferritic, Austenitic, and Martensitic.

FERRITIC (AISI 400 series)

These steels contain less than 0.10% carbon and are magnetic. Ferritic steels cannot be heat hardened and so cannot be welded well. Ferritic steels lack toughness, ductility, poor in extra elongation and susceptible to cracking at high temperature. These are less expensive and so used for certain applications such as for cold work. The general purpose grade is 430.

AUSTENITIC (AISI 200 and 300 series)

These stainless steels form the widest and most popular range of products (nearly 70%). These can be formed, welded and withstand cryogenic to red-hot temperatures. These steels can be made very strong by cold work, but are not harden-able by heat treatments. These are nonmagnetic. They contain between about 16 and 25% chromium. Nickel-containing steels are non-ferromagnetic and used for geophysical surveying equipment, X-ray scanners, etc.

MARTENSITIC (AISI 400 series)

These type of steels share some qualities with ferritic stainless steels, but have higher carbon content, up to 1%. The carbon content allows tempering and hardening such as for knives and tools. These steels are useful in conditions where strength of the steel supersedes the need for corrosion resistance. These steels are easy to machine but produce a serrating chip to a slowdown of the productivity. Martensitic stainless steels are selected for better tensile strength, creep, and fatigue strength properties, with reasonable corrosion and heat resistance.

Duplex steels are a combination of ferritic and austenitic steels. With addition of elements such as Aluminium, Copper and Niobium, Precipitation hardening steels become very strong.

Welding Martensitic Stainless Steels: Martensitic stainless steels are most difficult of the stainless steel alloys to weld. Higher carbon contents produce greater hardness and so chances of cracking. Localized stresses associated with Martensitic transformation, also cause cracking. Specific atmosphere (argon) welding reduces cracking.

SS and dairy processing plant

 

Stainless steels are used for curtain walls, spandrels panels, mullions, windows, doors, panelling, cladding, partitions, grills, louvers, railings, fascias, ceilings’ panels, signage base, stairs, toilets, basins, bathtubs, shower stalls, automobile components, trimmings, building hardware, furniture, cabinets, etc. In industry these are used for food and pharmaceutical machinery, chemical plants, reaction vessels, storage tankers, liquid packing drums and tins. Flexibility and elasticity permit construction of snap assemblies. Stainless steels are used for surgical instruments, equipment, body implants and orthopedic support systems. Stainless steels are used for high temperatures, such as in aircraft jet engines or gas turbines.

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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.

640px-hk_lantau_island_e6aca3e6beb3e98193_sunny_bay_road_20070616-11_highway_bridge

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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