A building consists of variety of barriers, such as the shell of the building, doors and widows, walls and roofs, for environmental control and safety.
Types of safety barricades are: Height related hazards, isolation of dangerous zones, exposure to effects of radiations, against high speed movements, security from anti social persons, theft, animals, etc.
Height related hazards require barricades. Nominally a fall of 600 mm is difficult to negotiate (climb up or down), so even for a normal adult it is considered a hazard. A provision of an intermediate step or support is required. For physically disable and infirm people a barricade may be necessary even when the height difference is only 25 mm. For situational conditions such as at the downward end of a ramp or slopping terrain, a fall of less than 300 mm requires a safety barricade. In buildings for human habitation a 900-mm minimum to 1100 mm optimum height for safety barricades like parapets, balustrades, etc., is prescribed on balconies, stair sides, and terrace edges of are prescribed. The height is often compromised to 790 mm or less by, alternatively, providing wider widths, for drama, cinema or assembly hall balcony fronts, to prevent visual obstruction to the view of the front edge of the stage.
HEIGHT FACTORED BARRICADES:
These are preventive barricades of specific height to control the crossover movement. Effective height actually available for the barricade is determined by the nature of the surroundings. A very steep gradient in front, and difficult to negotiate terrain (moats, pits, trenches) can also act as a barricade.
Effective height of a barricade system is affected by its configuration. A horizontal mid-bar or any such element can accommodate a toe of a user, to reduce the effective height of the available barricade. To prevent children less than five from falling, gaps in the balustrades (balcony and stairs) must not allow a 100-mm diameter sphere to pass through.
WIDTH FACTORED BARRICADES:
As shown earlier in case of safety barriers, width of the barricade compensates the height requirement. Barricades of greater widths are also required, when a structure is required to resist horizontal stresses and thrusts, as in case of retaining walls and dams. Walls and partitions of greater width with greater bulk (low density) are created as insulation system for heat, x ray or other radiations. Wider barricades cut off the view of areas immediately close-below, an ideal provision for stepped floor balconies in sea shore resorts.
PEDESTRIAN CONTROL BARRICADES:
Pedestrian barricades should be taller than approximately 2/5 the height of the tallest user, as for example for a mid-road verge. Security barricades should be taller than tallest persons to be barricaded. Often the effective width of the barricade structure controls the actual height required. Barbed wire fencing of Y and T, ‘shapes are used in jails and defence installations. Pedestrian control can be effected by notional barricades, like a thin rope, a horizontal pipe, a small ledge, a floor marking.
The barricades should take in to consideration, animals’ the capacity to leap and also the ‘run depth’ available in the surroundings. Animals are confined by a variety of methods including water-filled moats, dry moats, and wire-mesh fences. Animal traps at gates have gaps to trap the animal’s feet, and width to prevent a ‘non run’ leap. Wicket gates are intentionally made of narrow width and have a non linear passageway to prevent vehicles like cycles and animals.
TRAFFIC SAFETY BARRICADES:
Traffic safety barricades are meant to be safe, stable (wide based, secured or resilient enough to revert to the original position) and visible. Traffic barricades direct the flow of traffic, prevent unauthorized entry or exit from the designated areas or lanes.
CROWD MANAGEMENT BARRICADES:
Crowd management barricades are designed for the safety and security of people, control the direction of their travel and to control their numbers. Such barricades are temporary (occasional) and permanent. The barricades are designed with the height safety standards (the nominal balustrade height and leap over prevention), but in addition have a capacity to resist horizontal thrust. Such barricades are in place at the famous temple of Tirupati Balaji, South India, and at Ambaji Temple, Gujarat.
A security barricade is meant to prevent access or exit to a specific area, such as a hazardous zone, protection from theft, and forceful entry by terrorist. Security barricades may be designed to withstand assaults such as high speed impacts like a high speed or armoured vehicle. Some of the most important security barriers include: fort walls, the Great Wall of China, Dykes in Holland, Wall dividing East and West Berlin in Germany and quadruped sections on Bombay sea shores.
- BERLIN WALL: During the period from 1961 to 1989, East Germany built a barrier to close off the migration after about 2.5 million skilled workers, professionals, and intellectuals to west Germany. This barrier, the Berlin Wall, was first erected on the night of Aug. 12–13, 1961. The original wall, built of barbed wire and cinder blocks, was subsequently replaced by a series of concrete walls up to 5 mts high, that were topped with barbed wire and guarded with watchtowers, gun emplacements, and mines. By the 1980s this system of walls, electrified fences, and fortifications extended 45 km through Berlin, dividing the two parts of the city, and extended a further 120 km around West Berlin, separating it from the rest of East Germany.
- The Berlin Wall came to symbolize the Cold War's division of East from West Germany and of eastern from western Europe. Yet, about 5,000 East Germans managed to cross the Berlin Wall (by various means) and reach West Berlin safely, while another 5,000 were captured by East German authorities in the attempt and 191 more were killed during the actual crossing of the wall.
- During October 1989 during the wave of democratization swept through eastern Europe and on November 9 the East German government had to open the country's borders with West Germany (including West Berlin). East Germans could travel freely now to the West.
BARRICADES FOR VEHICLE CONTROL:
Guard rails are used to prevent vehicles from veering off a road into oncoming traffic, crashing against solid objects (like a bridge pillar) or falling into a ravine. Guard rails are designed with an objective to keep the vehicle upright while it is deflected along the guard rail. Vehicle barriers are generally taller than ½ the diameter of the wheel. A tall guard rail of ideal height for a car, though may not keep a truck from toppling over it, whereas a thin vehicle like a motorbike may slip under a high rail. Vehicle barriers on bridge sides, auto-ways, should be capable of resisting (strength) and deflecting (shape) the impact of cars, lorries, etc.
One-way streets and gates have small stepped fall at entry points to prevent exit of the vehicles. Wharfs, boats and ships use rubber buffers or tyres as preventive barriers against impact and rubbing.
BARRICADES FOR OPENINGS:
Barricades are required in openings like Doors, Windows, Gaps, etc. These are required for fall related hazards and for controlling the entry or exit of human beings, animals, pets, flies and insects, and mosquitoes. Barriers are also required for environmental controls, such as heat, solar radiation, breezes, odours, audio. Barriers such as the louvres are required in openings to control vision in and out.
Barricades for a fall-related hazard are required if the sill level is lower than height required for a balustrade in a similar position. Barricades are also required if a piece of furniture against an opening like a window is likely to reduce the effective sill level. Barricades within the doors are required in nursery areas, stair ways, etc. where infants are likely to crawl.
Soft barricades of cloth, plastic or fibre tapes and ropes are used as a visual boundary or indicative barrier by police and military to isolate sensitive zones.