michelle's blog

2005-11-22T05:03:00.000-08:00

Arch structures

An arch is a curved structure capable of spanning a space while supporting significant weight (e.g. a doorway in a stone wall). The arch was developed in Mesopotamia, Assyria Egypt and Etruria. It was later refined in Ancient Rome. The arch became an important technique in cathedral building and is still used today in some modern structures as for example in bridges.

History

Before the development of the arch, the principal method of spanning a space was the simple post-and-beam construction , in which a horizontal beam is supported by two columns. This type of construction was used to build the great Greek temples. The columns of these temples are closely spaced because of the limited length of available stones. Much larger spans can now be achieved using steel beams, but the spans are limited because the beams tend to sag under heavy loads.Arches were used by the Egyptian, Babylonian, Greek and Assyrian civilizations for underground structures such as drains and vaults, but the ancient Romans were the first to use them widely above ground. The so-called Roman arch is semicircular, and built from an odd number of arch bricks (in modern architectural parlance, these are called voussoirs). The capstone or keystone is the topmost stone in the arch. This shape is the simplest to build, but not the strongest. There is a tendency for the sides to bulge outwards, which must be counteracted by an added weight of masonry to push them inwards.

The semicircular arch can be flattened to make an elliptical arch. The horseshoe arch is based on the semicircular arch, but its lower ends are extended further round the circle until they start to converge. It was used in Spanish Visigothic architecture, Islamic architecture, as in the Great Mosque of Damascus and in later Moorish buildings. It was used for decoration rather than for strength. The semicircular arch was followed in Europe by the pointed Gothic arch or ogive, whose centreline more closely followed the forces of compression and which was therefore stronger. This design had been used by the Assyrians as early as 722 BC. The parabolic and catenary arches are now known to be the theoretically strongest forms.Another important architectural innovation was the pointed Gothic arch. This type of structure was first used in Europe beginning in the 12th century, followed by the construction of several magnificent Gothic cathedrals in France in the 13th century. One of the most striking features of these cathedrals is their extreme height.

Construction

An arch requires all of its elements to hold it together. This raises the interesting question of how an arch is actually constructed. One simple answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting. For an arch higher than head height, scaffolding would in any case be required by the builders, so the scaffolding can be combined with the arch support.

Arches Bridges

After girders, arches are the second oldest bridge type and a classic structure. Unlike simple girder bridges, arches are well suited to the use of stone. Many ancient and well know examples of stone arches still stand to this day. Arches are good choices for crossing valleys and rivers since the arch doesn't require piers in the center. Arches can be one of the more beautiful bridge types.

Arch nowadays

With the advent of more advanced methods of structural analysis, it has become possible to determine the optimum shape of an arch under given load conditions

Framed Structures

A framed structure in any material is one that is made stable by a skeleton that is able to stand by itself as a rigid structure without depending on floors or walls to resist deformation.Alaska Building, Seattle's first steel-framed skyscraper, is completed in 1904.From 1903 to 1904, Seattle's tallest building and first steel-framed skyscraper is constructed. The Alaska Building, located at the southeast corner of 2nd Avenue and Cherry Street, rises 14 stories high.Earmes & Young, a St. Louis architectural firm, with assistance by Seattle architects Saunders & Lawton, designed the building. The Alaska Building remained the tallest building in Seattle until the 18 story Hoge Building (705 2nd Avenue) was completed in 1911.Materials such as wood, steel, and reinforced concrete, which are strong in both tension and compression, make the best members for framing. Masonry skeletons, which cannot be made rigid without walls, are not frames. The heavy timber frame, in which large posts, spaced relatively far apart, support thick floor and roof beams, was the commonest type of construction in eastern Asia and northern Europe from prehistoric times to the mid-19th century. It was supplanted by the American light wood frame (balloon frame), composed of many small and closely spaced members that could be handled easily and assembled quickly by nailing instead of by the slow joinery and dowelling of the past. Construction is similar in the two systems, since they are both based on the post-and-lintel principle. Posts must rest on a level, waterproof foundation, usually composed of masonry or concrete, on which the sill (base member) is attached. Each upper story is laid on crossbeams that are supported on the exterior wall by horizontal members. Interior walls give additional beam support.In the heavy-timber system, the beams are strong enough to allow the upper story and roof to project beyond the plane of the ground-floor posts, increasing the space and weather protection. The members are usually exposed on the exterior. In China, Korea, and Japan, spaces between are enclosed by light screen walls and in northern Europe partly by thinner bracing members and partly by boards, panels, or (in half-timbered construction) bricks or earth.The light frame, however, is sheathed with vertical or horizontal boarding or shingling, which is jointed or overlapped for weather protection. Sheathing helps to brace as well as to protect the frame, so the frame is not structurally independent as in steel frame construction. The light-frame system has not been significantly improved since its introduction, and it lags behind other modern techniques. Prefabricated panels designed to reduce the growing cost of construction have not been widely adopted. Modern heavy-timber and laminated-wood techniques, however, provide means of building up compound members for trusses and arches that challenge steel construction for certain large-scale projects in areas where wood is plentiful.Steel framing is based on the same principles but is much simplified by the far greater strength of the material, which provides more rigidity with fewer members. The load-bearing capacity of steel is adequate for buildings many times higher than those made of other materials. Because the column and beam are fused by riveting or welding, stresses are distributed between them, and both can be longer and lighter than in structures in which they work independently as post-and-lintel. Thus, large cubic spaces can be spanned by four columns and four beams, and buildings of almost any size can be produced by joining cubes in height and width. Since structural steel must be protected from corrosion, the skeleton is either covered by curtain walls or surfaced in concrete or, more rarely, painted. The steel frame is used also in single-story buildings where large spans are required. The simple cube then can be abandoned for covering systems employing arches, trusses, and other elements in a limitless variety of forms in order to suit the functions of the building.

Chicago...

2005-11-06T21:50:00.000-08:00

I think that the video of Chicago was very intersting, because in may case I don't know about this city. Chicago is a city in United States and is very famous in the World for the skycrapers! In a few scuare this city have marvelous buildings. The auditorium of Chicago is my favorite because it has a marvelous desing and is really beautiful!!!

Glass...

2005-11-06T21:21:00.000-08:00

The materials definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly to below its glass transition temperature, thereby not giving enough time for a regular crystal lattice to form. A simple example is when table sugar is melted and cooled rapidly by dumping the liquid sugar onto a cold surface. The resulting solid is amorphous, not crystalline like the sugar was originally, which can be seen in its conchoidal fracture. The word glass comes from Latin glacies (ice) and corresponds to German Glas, M.E. glas, A.S. glaes. Germanic tribes used the word glaes to describe amber, recorded by Roman historians as glaesum. Anglo-Saxons used the word glaer for amber. The remainder of this article will be concerned with a specific type of glass—the silica-based glasses in common use as a building, container or decorative material. In its pure form, glass is a transparent, relatively strong, hard-wearing, essentially inert, and biologically inactive material which can be formed with very smooth and impervious surfaces. These desirable properties lead to a great many uses of glass. Glass is, however, brittle and will break into sharp shards. These properties can be modified, or even changed entirely, with the addition of other compounds or heat treatment. Common glass is mostly amorphous silicon dioxide (Si O2), which is the same chemical compound found in quartz, or in its polycrystalline form, sand. One of the most obvious characteristics of ordinary glass is that it is transparent to visible light (not all glassy materials are). The transparency is due to an absence of electronic transition states in the range of visible light, and to the fact that such glass is homogeneous on all length scales greater than about a wavelength of visible light (inhomogeneities cause light to be scattered, breaking up any coherent image transmission). Ordinary glass does not allow light at a wavelength of lower than 400 nm, also known as ultraviolet light or UV, to pass. This is due to the addition of compounds such as soda ash (sodium carbonate). Pure SiO2 glass (also called fused quartz) does not absorb UV light and is used for applications that require transparency in this region, although it is more expensive. This type of glass can be made so pure that hundreds of kilometres of glass are transparent at infrared wavelengths in fibre optic cables. Individual fibers are given an equally transparent cladding of SiO2/GeO2 glass, which has only slightly different optical properties (the germanium contributing to a lower index of refraction). Undersea cables have sections doped with erbium, which amplify transmitted signals by laser emission from within the glass itself. Amorphous SiO2 is also used as a dielectric material in integrated circuits, due to the smooth and electrically neutral interface it forms with silicon.Glasses used for making optical devices are commonly categorized using a letter-number code from the Schott Glass catalog. For example, BK7 is a low-dispersion borosilicate crown glass, and SF10 is a high-dispersion dense flint glass. The glasses are arranged by composition, refractive index, and Abbe number.Glass is sometimes created naturally from volcanic magma. This glass is called obsidian, and is usually black with impurities. Obsidian is a raw material for flint knappers, who have used it to make extremely sharp knives since the stone age. Obsidian collection is prohibited by law in some places (including the United States), but the same toolmaking techniques can be applied to industrially-made glass.
Glass and its Fascinating History Spanning more than 5000 Years, Isn't it fascinating how a glass container - or even a work of art for that matter - can originate from a molten gob of glowing glass? But it's no wonder that the fascination with this creative process has spanned centuries - from the ancient Egyptians some 3000 B.C. to the 21st Century. The fact remains: Glass continues to play a vital part in eveWith the advent of glass blowing in 200 B.C. in cities such as Alexandria, that which was once reserved only for regal privilege became an indispensable means for goods shipment and decisive factor in promoting trade and commerce. The advantages of glass as a material are immediately apparent and have been known for centuries. Refined additives have been systematically improved to affect major parameters such as melting point, glass durability, and homogeneity of the glass stream, color, and color consistency. Generations of glassblowers have also made a substantial contribution to the unique reputation of glass. Today, artisans all over the world have raised glassblowing to a fine art. Glass Packaging - more than just a Packaging Solution. As a material, glass has out-standing properties, and its advantages have been successfully harnessed by innovative glass plants to further promote its competitive edge. Highly original packaging concepts bolster the uniqueness of a product, and hence, its image. Whatever your packaging demands - Glass can provide the solution to your needs because of the high flexibility it lends to container design.
(http://en.wikipedia.org/wiki/Glass)
(http://www.emhartglass.com/whyglass/keypropadvan.asp)

Wood

2005-11-06T20:47:00.000-08:00

Building materials are selected based a number of factors in addition to durability including, but not limited to, cost, availability, ease of construction, thermal performance, and aesthetics. Wood performs equally or better compared with other building materials in all of these categories. As with all materials, wood is susceptible to deterioration under specific adverse conditions. However, with proper design detailing, good construction techniques and adequate building maintenance, wood structures can be expected to last an exceedingly long time. Wood has been used as a durable building material for thousands of years and the historic wood buildings still standing today are a testament to that. For buildings where longevity is important, many designers don’t consider wood – it is commonly assumed that wood structures have shorter service lives than buildings made of other materials.
In addition, there are many specific applications where the natural durability properties of wood make it the material of choice.
Wood is resistant to some of the chemicals destructive to steel and concrete. For example, wood is often the material of choice when exposed to: organic compounds, hot or cold solutions of acids or neutral salts, dilute acids, industrial stack gases, sea air and high relative humidity. Because of its resistance to chemicals wood is often used in the following applications:
Potash storage buildings
Salt storage domes
Cooling towers
Industrial tanks for various types of chemicals
With thoughtful design and careful workmanship wood bridges prove to be remarkably durable. Throughout the world, there are numerous examples of long lasting wooden bridges - both historic and modern. Modern bridge decks are subjected to relentless attack of de-icing chemicals, and wood is gaining acceptance as a viable option for these applications.
Pilings that are constantly submerged in fresh water have been known to last for centuries. Foundation piles under structures will not decay if the water table remains higher than the pile tops. Many of the world's important structures are built on wood piles including much of the city of Venice and the Empire State Building in New York.
Wood derives from woody plants, notably trees but also shrubs. Wood from the latter is only produced in small sizes, reducing the diversity of uses. Wood is a hygrosco pic, cellular and anisotropic material. Dry wood is composed of fibers of cellulose (40%–50%) and hemicellulose (20%–30%) held together by lignin (25%–30%). Wood has been used by man for millenia for many purposes, being many things to many people. One of its primary uses is as fuel. It may also be used as a material, for making artworks, boats, buildings, furniture, ships, tools, weapons, etc. Wood has been an important construction material since humans began building shelters, and remains in plentiful use today. Construction wood is commonly known as timber in International English, and lumber in American English. Wood may be broken down and be made into chipboard, engineered wood, hardboard, medium-density fibreboard (MDF), oriented strand board (OSB), paper or used to make other synthetic substances.
(http://www.durable-wood.com/heritage/advantages.php)
(http://www.ukrainianmuseum.org/pics/wooden.jpg)
(http://en.wikipedia.org/wiki/Wood)

Concrete...

2005-11-06T20:37:00.000-08:00

In construction,concrete is a composite building material made from the combination of aggregate and cement binder. The most common form of concrete is Portland cement concrete, which consists of mineral aggregate (generally gravel and sand), Portland cement and water. It is commonly believed that concrete dries after mixing and placement. Actually, concrete does not solidify because water evaporates, but rather cement hydrat es, gluing the other components together and eventually creating a stone-like material. When used in the generic sense, this is the material referred to by the term concrete. Concrete is used to make pavements, building structures, foundations, motorways/roads, overpasses, parking structures, bases for gates/fences/poles, and cement in brick or block walls. An old name for concrete is liquid stone.The Assyrians and Babylonians used clay as cement in their concretes.
The Egyptians used lime and gypsum cement. In the Roman Empire, cements made from pozzolanic ash/pozzolana and an aggregate made from pumice were used to make a concrete very similar to modern portland cement concrete. In 1756, British engineer John Smeaton pioneered the use of portland cement in concrete, using pebbles and powdered brick as aggregate. In the modern day, the use of recycled/reused materials as concrete ingredients is gaining popularity due to increasingly stringent environmental legislation. The most conspicuous of these is pulverized fuel ash, recycled from the ash by-products of coal power plants. This has a significant impact in reducing the amount of quarrying and the ever-attenuating landfill space.During hydration and hardening, concrete needs to develop certain physical and chemical properties, among others, mechanical strength, low permeability to ingress of moisture, and chemical and volume stability. Concrete has relatively high compressive strength, but significantly lower tensile strength (about 10% of the compressive strength). As a result, concrete always fails from tensile stresses - even when loaded in compression. The practical implication of these facts is that concrete elements that are subjected to tensile stresses must be reinforced. Concrete is most often constructed with the addition of steel bar or fiber reinforcement. The reinforcement can be by bars (rebars), mesh, or fibres to produce reinforced concrete.
Concrete can also be prestressed (reducing tensile stress) using steel cables, allowing for beams or slabs with a longer span than is practical with reinforced concrete. The ultimate strength of concrete is related to water/cement ratio and the size, shape, and strength of the aggregate used. Concrete with lower water/cement ratio (down to 0.35) makes a stronger concrete than a higher ratio. Concrete made with small (1/2" or 12mm) smooth pebbles is much weaker than that made with larger (1" or 25mm) rough-surfaced broken rock pieces for example. Certain shapes are very strong in compression, such as arches and vaults, and are therefore preferred for concrete construction. Concrete is placed in a wet or plastic state, and therefore can be manipulated and molded as needed. Hydration and hardening of concrete may lead to tensile stresses at a time when it has not yet gained significant strength, resulting in shrinkage cracks. However, when concrete mix is placed in accordance with the best recommended practice, cracking may be minimal.
Cocrete is like putty in the hands of an architec or engenieer. It's easy too manipulate. It can take any share, turn any colour, mimic any texture, spam great distances and weather any storm.
(http://www.cement.ca/cement.nsf/0/04E78E71C998827A85256AA4006131EB?OpenDocument)
(http://en.wikipedia.org/wiki/Concrete)
(http://encarta.msn.com/encyclopedia_761558777/Concrete_(construction).html)

2005-11-06T19:44:00.000-08:00

Examples of uses of brick in Urban Planning

2005-11-06T18:56:00.000-08:00

2005-11-06T16:46:00.000-08:00

Uses of Brinck in Urban Planning:

Brick is a material that have very advantages. In the past this material was used for construction buildings, in especial for building's ornament. Nowdays brick is use no only for the buildigs, also is use for the definitions of the spaces inside the city. This material is choose for put in social space for its characteristics. Brick is use in urban mobiliary and walks for persons. A good example the use of Brick in Urban Planning is actualliy in Chacao.

2005-10-23T20:24:00.000-07:00

STONE.......

Stone is a materials used for the construction of monumental architecture. This material has different advantages, is durability, adaptability and it can be used in modest structures but also, it has disadvantages because is difficult to quarry, transport and cut.
There are different types of stones. Rubble is stonework simplest and cheapest, ashlar masonry is the stone most used for monumental architecture, and the entablatures used for example in the construction of an ancient Greek.
The stones are good for resist deformation and it is strong enough to provide monolithic support. Also, the stones can be used for roofing.
Stones were used since the Stone Age and still in the actuality is use for the construction of buildings.

brain map

2005-10-23T19:35:00.000-07:00

2005-10-18T09:35:00.000-07:00

A good Paragraph....
The first for do a good paragraph is have the main idea, after is necessary develop this topic with other ideas (the second ideas explain the main idea). Also, is importand for write a paragraph no repeat the words because the paragraphs will be boring. Is usually the use of conectors in the text, for have the relation between the ideas that the person want express. the cohesion and organization are too other aspects necessary for understand the text. Finally is importand end the paragraph with a conclusion.

2005-10-11T09:40:00.000-07:00

Hello!!!
Welcome to my blog!! Here, I'll public coments about Urban Planning and Architecture. Also, I'll the most important definitions about the work of the Urban Planners in the city.

Bye!!!