Glass - PowerPoint Presentation

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Glass

Glass is a material which is used in every day life.

It is a mixture of sand,

soda ash, lime

stone, and small various elements to control

color, then heated to form glass.

When drawn into small pieces

, glass is stronger than steel, though

not nearly as stiff.

In larger pieces,

the microscopic imperfections that are an inherent characteristic of glass reduce its useful strength to

significantly

lower levels, particularly intension.When a

surf

ace of a sheet of glass is placed in sufi

cient

tension,

as happens when an object strikes the glass, cracks propagate from an imperfection near the point of maximum tension and the glass shatters.Slide3

Glass

The origins of glass are lost in pre

h

istory

.

Initially a material for colored beads and small bottles, glass was fi

rst used in windows in Roman times.

The largest known piece of Roman

glass, a sheet used for a window

in a public bath at Pompeii, was nearly 3 by 4 feet (800 by 1100 mm) in size.

Today, it takes many forms in buildings

. C

hurch windows made of thousands of jewel-like pieces of colored glass

.

Skyscrapers that shimmer in facets of

reflective glass mirroring the sky.Slide4

Basic information about glass

Transparent material

Transmit and reflect daylight, different coefficient of transmission during day and night

Usually it has density about 2500 kg/m3

U

ndesirable

characteristic of being brittle

and subject to

shattering under shock.

Difference according to thicknes

(from

1

to

19

mm)

Used like subdivision element

Reflection during night are exciting

and because of that glass is used inExternal parts of skyscrapers Slide5

Types of glasses

Float:

the most widely used method of molten glass manufactured

.

This glass is more commonly known as window glass

. M

ade by floating molten glass on a bed of molten tin. This method gives the glass uniform thickness and a very flat surface.

It gives full transparency.

Also used for

mirror

plate,

furniture and

decoration

.Slide6

Types of glasses

Antique:

or restoration glass is either true antique glass that has been salvaged or it is authentically reproduced or

artificially simulated. Slight distortions, occasional pits and other imperfections characterize most antique glass.

Bent:

glass that is curved, bent at an angle, spherical or segmented portions of same.Slide7

Types of glasses

Beveled

:

panels of straight line or

curved glass with a beveled perimeter edge for elegant look.

The beveled angle is variable and dependent

upon the bevel width and the thickness of glass required.

Generally, the wider the beveled edge, the thicker the glass.

Beveled glass can

also be incorporated in sealed insulating panels and a wide variety of shapes

and sizes are available.Slide8

Types of glasses

Etched & Frosted:

glass that is rendered opaque from chemical wash or sandblasting. Often, intricate designs are

permanently applied to various types of clear glass.

A sheet of frosted glass is an excellent privacy aid because it admits light without allowing people to see through it.

Decorative patterns may be used Slide9

Types of glasses

Fiberglass:

is not real glass but rather includes epoxy resins and glass fibers. Available in various colors

.F

iberglass is not recommended for use in sealed insulating units because the various sealing agents may interact with the

fiberglass and deteriorate.

It is a lightweight, extremely strong, and

forcefulmaterial.Slide10

Types of glasses

Plexiglass

:

It is derived from natural gas, turned into a clear, watery white liquid, heated to form a transparent solid shape - nearly any solid shape. Acrylics are then manufactured into large sheets, rods, tubes, profiles and specific shape designs.

However,

plexiglass scratches easily and can become brittle in cold temperatures

.Slide11

Types of glasses

Stained

:

glass that is manufactured with various pigments.

Not to be confused with painted glass, stained glass

contains its specific coloration during the molten state of glass manufacturing.

This is made by adding metallic salts during its manufacture.

Mostly used for decoration.Slide12

Types of glasses

Leaded:

a variety of glass that is assembled in usually intricate curved and straight line patterns and connected

together with lead or other metalic came.

Leaded glass is usually associated with stained glass and is not recommended in unprotected applications.

Sunlite

decreases the strength of lead came causing the glass plane to warp and weaken. In many large windows, steel frames

replace leaded came.Slide13

Types of glasses

Heat-Treated Glass:

This glass is produced by reheating

annealed glass in an oven to approximately 1800 degrees Fahrenheit

(980 C) and then cooling both of its surfaces rapidly with blasts of air

while its core cools much more slowly.

This process induces permanent compressive stresses in the edges and faces of the glass and tensile

stresses in the core. The

result is a glass stronger in bending than annealed glass and more resistant to thermal stress and impact. These properties make heat-treated glass useful for windows exposed to

heavy wind pressures, impact, or intense heat or cold.Slide14

Types of glasses

Tempered glass

:

has higher residual stresses than heat-strengthened glass and is about four times as strong in bending as annealed glass.

If it is break broken, the sudden release of its internal stresses reduces tempered glass instantaneously to small, square-edged granules rather than long, sharp-edged shards.

Tempered glass is more costly than annealed glass. It often has noticeable optical distortions created by the tempering process.Slide15

Types of glasses

Heat-strengthened

glass is about twice as strong in bending annealed glass and is more resistant to thermal stress.

It usually has fewer distortions than tempered glass. Its breakage behavior is more like that of annealed glass than tempered glass.

It cannot be used where safety glazing is required except in laminated form .Slide16

Types of glasses

Laminated

glass is made by sandwiching a transparent polyvinyl

butyral

(PVB) interlayer between sheets of glass and bonding the three layers together under heat and pressure.Laminated glass is not as strong as annealed glass of the same thickness, but when laminated glass breaks, the soft interlayer holds the shards of glass in place rather than allowing them to fall out of the frame of the window.

This makes laminated glass useful for skylights and overhead glazing, because it reduces the risk of injury to people below in case of breakage.

Laminated glass is a better barrier to the transmission of sound than solid glass.Slide17

Types of glasses

Chemically strengthened glass

The temperatures involved in chemical strengthening are lower, chemically strengthened glass does not experience the optical distortions or warping that are common with heat-treated glass.

It can be cut after strengthening, although its strength is diminished along the cut edges.

When chemically strengthened glass breaks, it produces large, hazardous shards. Slide18

Types of glasses

Fire-Rated Glass

is used in doors, windows, curtain walls like a protection from fire and smoke during fire.

Wired glass is produced by rolling a mesh of small wires into a sheet of hot glass. When wired glass breaks from thermal stress, the wires hold the sheets of glass in place so that the glass continues to act as a re barrier.

This can make a barrier up to 45 minutes.Slide19

Types of glasses

Spandrel Glass

Spandrel glass is a type of glass that is used to cover construction materials. In addition to being entirely durable, spandrel glass can also be used in an aesthetically appealing way. Spandrel is commonly used between certain sections of a building including the area between floors, columns, ceilings, and other small or large spaces.

Spandrel glass is available in numerous shades ranging from green to bronze.Slide20

Types of glasses

Tinted glass

is made by adding small amounts of selected chemical elements to the molten glass mixture to produce the desired hue and intensity of color in grays, bronzes, blues, greens, and

golds

. By tinting glass, its visible light transmittance is reduced.

The visible light transmittance of commercially available tinted glass-

es ranges from about 0.75 in the lightest tints to 0.10 for dark gray.Slide21

Types of glasses

Fritted Glass

Frits are used to create special opaque glasses for covering spandrel areas (the bands of wall around the edges of doors) in glass curtain wall construction. A uniform coating of frit is applied to what will be the interior surface of the glass.

After the frit has been printed on the glass, the glass is dried and then red in a tempering furnace, transforming the frit into a hard, permanent ceramic coating. Many colors are possible in both translucent and opaque finishes.Slide22

Types of glasses

Refl ective Coated Glass

Thin, durable layer of metal or metal oxide can be deposited on a surface of either clear or tinted glass sheets under closely controlled conditions to make

reflective

coated glass, also called solar control glass.

Depending on its composition, the layer may be applied to either the inside of the glass or the outside.Slide23

Glazing

Window glass is a poor thermal insulator.

A single sheet of glass

(single glazing) conducts heat about 5 times as fast as 1 inch (25 mm) of polystyrene foam insulation and 20 times as fast as a well-insulated wall.

A second sheet of glass

applied to a window with an airspace between the two sheets(double glazing) cuts this rate of heat loss in half.

A third sheet with its additional airspace (triple glazing) reduces the rate of heat loss to about a third of the rate through a single sheet. A triple-glazed window, however, still loses heat about six times as fast as the wall in which it is placed.Slide24

Low-Emissivity Coated Glass

Low-e coatings

are ultrathin, virtually transparent, and almost colorless metallic coatings that selectively reject solar radiation of different wavelengths.

They have a high visible light transmittance and, depending on the particular coating, a low transmittance for some or all types of infrared radiation (heat).

Low-e coated glass is most commonly used as one of the two lights in double glazing, where it offers several benefitsSlide25

Self-Cleaning Glass

Glass tends to attract dirt, and must be washed periodically both inside and out to maintain its transparency.

Self-cleaning glass is coated with titanium oxide on its exterior surface.

This coating acts as a catalyst that enables sunlight to convert organic dirt to carbon dioxide and water.

It also causes rainwater to run down the surface in sheets rather than to bead up. Nonorganic dirt, such as sand, is unaffected by the catalyst, but the sheets of water are more effective at removing such matter than beaded water. Slide26

Smart glass

Glass that can change its optical properties is called

chromogenic

glass.

Thermochromic glass

becomes darker when it is warmed by the sun.Photochromic

glass becomes darker when exposed to bright light.

Electrochromic glass

changes its transparency in response to the passage of electric current.Antireflective

glass minimizes residual reflections that normally occur when light levels differ significantly on the opposite sides of glass.

It is used for glazing in showrooms, display areas, sports stadiums, art-work framing, and other applications where the highest possible optical quality is desired. Slide27

Mirrors

They totally reflect light and make a picture.

Mirrors are made of mirror glass, which has a thin silver based coating on its back side. A thin layer of copper applied over the silver prevents corrosion, and a second layer of backing paint provides additional protection

.

Might be float or curved.Slide28

Plastic Glazing Sheets

Transparent plastic sheet materials are often used instead of glass for specialized glazing applications.

The two most common plastic glazing materials are

acrylic

and polycarbonate

.Both are more expensive than ordinary float glass. Both have very high

coeficients of thermal expansion, which cause them not merely to expand and contract with temperature changes, but also to bow visibly toward the warm side when subjected to high indo or outdoor temperature differentials.

This, in turn, requires that plastic sheet materials be installed in their frames with relatively expensive glazing details that allow for plenty of linear movement and rotation.

Both polycarbonate and acrylic are soft and easily scratched, although more scratch-resistant formulations are available. Slide29

Aerogel-Filled Glazing

Aerogel

, a silicon-based foam that is 99.8 percent air, can be used to fill the cavity in double-glazed glass or plastic products.

It is milky in color, not fully transparent, and has a visible transmittance that varies with its thickness.

It has a small density and very good insulation properties.

This type of glazing has a good light to solar gain ratio, making it an

effcient source of diffuse, low-contrast, natural daylight.Slide30

GlazingSlide31

GlazingSlide32

Glazing

The design objectives for a large light glazing system are:

1.

To support the weight of the glass in such a way that the glass is not subjected to intense or abnormal stress patterns

2. To support the glass against wind pressure and suction

3. To isolate the glass from the effects of structural deflections in the frame of the building and in the smaller framework of mullions that supports the glass

4. To allow for expansion and contraction of both glass and frame without damage to either

5. To avoid contact of the glass with the frame of the window or with any other material that could abrade or stress the glassSlide33

Thank you for your attention

Made by:

Amel

Adilovic