In most cities of the world that were planned, rather than developing gradually over a long period of time, streets are typically laid out on a grid plan, so that city blocks are square or rectangular. Using the perimeter block development principle, city blocks are developed so that buildings are located along the perimeter of the block, with entrances facing the street, and semiprivate courtyards in the rear of the buildings. This arrangement is intended to provide good social interaction among people.

Guard rail

Guard rail or guardrail, sometimes referred to as guide rail or railing, is a system designed to keep people or vehicles from (in most cases unintentionally)

straying into dangerous or off-limits areas. A handrail is less restrictive than a
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guard rail and provides both support and the protective limitation of a
boundary.	Д
Most public spaces are fitted with guard rails as a means of protection

against accidental falls. Any abrupt change in elevation where the higher portion is accessible makes a fall possible. Due to this responsibility and liability, rails are placed to protect people using the premises. Guardrails are generally required by code where there is a drop of 30" or more.

Examples of this are both architectural and environmental. Environmental

guard rails are placed along hiking trails where adjacent terrain is steep.
Railings may also be located at scenicАoverlooks (рис. 50, 51).
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и
С
Рис. 50		Рис. 51

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Guard rails in buildings are numerous, and are required by building codes in many circumstances. Guard rails along stairways are common, and catwalks and balconies are also lined with them. The most common residential guard rail is usually a wood railing around the deck. This typically is built on-site from pressure treated lumber, featuring a simplistic design of vertical baluster spaced every 3.5" to comply with building code. Other guard rail construction options are available. Cable railings typically use stainless steel cables strung horizontally. Glass balusters and glass panels open the view while still providing safety, as at the Grand Canyon Skywalk. With the increasing popularity of composite lumber for decking, manufacturers, like Timber Tech are providing composite railing components. Another option is Mountain laurel handrail made with woven branches of the mountain laurel tree. Wrought iron

is another choice that is traditional and sturdy.

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Building codes also require that no opening in a guard be of a size such that a 4" sphere may pass. There are three exceptions according to the 2003 International Building Code Section 1012.3 which allow openings to not exceed 8" or 21" depending on occupancy groups or special areas.

An architect who was famous for creative use of handrails for social stability was Alvar Aalto. The guard rails of an observation tower such as the

flat area in either a landscape (such as a park or garden) or protruding from a building.

Space Needle or Eiffel Tower become exaggerated to the point of becoming a
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fence or cage. This is also done on bridges and overpasses to prevent accidents
and suicides.			А
			Terrace
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A terrace is an architectural term used primarily to describe an external
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Terraces are used primarily for leisure activity such as sitting, strolling, or resting. The term also often applies to a raised area in front of a monumental building or structure, which is usually reached by a grand staircase and surrounded by a balustrade. Terraces need not always protrude from a building; a flat roof area (which may or may not be surrounded by a balustrade) used for social activity is known as a roof terrace.

A terrace may be supported by an embankment or solid foundation, either natural or man-made. Terraces may also be platforms, supported by columns but without the space below filled in.

Terraces are always open to the sky, but may or may not be paved (рис. 52, 53).

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Рис. 52		Д		Рис. 53
	Race course
	А
A race track (or 'racetrack', 'racing track' or 'racing circuit') is a facility
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built for racing of animals (e.g. horse racing or greyhound racing), vehicles, or

athletes. A race trackСalsoиmay feature grandstands or concourses. Racetracks are also used in the study of animal locomotion. Some motorsport tracks are called speedways.

A racetrack is a permanent facility or building. Racecourse is an alternate term for a horse racing track, found in countries such as the United Kingdom, Australia, Hong Kong, and the United Arab Emirates. Race tracks built for bicycles are known as velodromes. Circuit is a common alternate term for racetrack, given the usual circuitous configuration of most race tracks, allowing races to occur over several laps.

A race course, as opposed to a racecourse, is a term for non-permanent tracks for sports, particularly road running, water sports, road racing, or rallying. Many sports usually held on racetracks also can occur on temporary tracks, such as the Monaco Grand Prix in Formula One (рис. 54).

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Рис. 54

Viaduct	И

it is a modern derivation from an analogyДwith aqueduct. Like the Roman aqueducts, many early viaductsбcomprised a series of arches of roughly equal length. Viaducts may span land or water or both.

A viaduct is a bridge composed of several small spans for crossing a

valley or a gorge. The term viaduct is derived from the Latin via for road and ductare to lead something. However,Аthe ancient Romans did not use the term;

The longest viaductиin antiquity may have been the Pont Serme which crossed wide marshes in southern France. In Romance languages, the word viaduct refers to Сa bridge which spans only land. A bridge spanning water is called ponte (рис. 55, 56).

Рис. 55

Рис. 56

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