stairs
The stair is a series of steps arranged one above the other varied platforms known as landings. Stairs are provided for access to and descent from the upper. Stories of a building that is for the communication between the storeys. Therefore they must provide an easy, safe and comfortable climb and descent. The total height of a stair is the rise; the total horizontal distance between the top and bottom steps is the run. A series of steps without landing is called a flight. The horizontal surface of a step is called its tread, and the vertical front its riser. The practice has demonstrated that definite proportions of riser (read are safe and easy. For interior stairs twice the height of the riser, plus the length of the tread, should b.23 inches. The general requirements for the stairs:.
1) Stairs must be fireproof;.
2) Each flight should consist of 5 t.
18 steps;.
3) All treads should be equal and all risers should be equal in any one flight; 4) Stair treads should be level and with smooth surface; 5) The angle of stairs with horizontal should be betwee.
30 and36 degrees; 6) All stairs should be equipped with handrail.
36 inches in height.
7) Stairs may be constructed of wood, stone, steel and reinforced concrete. a) Types of Stairs Stairs may be classified as standard, monumental and emergency according to their use. Standard stairs are constructed for constant and every day use in structures without lifts. They must provide an easy passage from one storey to another. Monumental stairs are constructed for architectural effect and use. Emergency stairs are the stairs in high structures where lifts are used, but where stairs must be provided from top to bottom. In case of fire they may be the only means of escape for the occupants. b) Stone and Marble Staircases Modern stone and marble staircases are of two main types. In the stone staircase the exposed treads and risers form themselves the structural elements. In the marble staircase the treads and riser are supported upon a separate structural base which may consist of a masonry vault, a steel framework or a reinforced concrete slat In the first type (a stone one) in which the steps are structural, the staircase is usually built into a wall at one side. Each step rests for a small distance upon the step below and is built into the wall for a distance sufficient to make the weight of the wall above to prevent it from turning. The undersides of the steps, where they are exposed, are often cut to form an inclined surface, following the slope of the stairs, and may be decorated with panels or carvings or other ornaments. This type of stair can be used for straight and curved runs and is largely) used for monumental entrance halls, where the stair fills a nice in front of the door. In such staircases the railing is usually of metal. c) Wooden Staircases These staircases can be divided into two classes: closed-and open-string stairs. In both classes the support is given by still timbers which follow the slope of the stairs and are cut to the shape Of the underside of the steps. The structural strength for a wooden staircase is usually obtained by constructing a heavy member, called a header, at the top and bottom of every run. In modern staircases of this type additional strength is obtained by inserting iron or steel bands into the handrail. d) Steel Staircases These staircases have become almost universal in modern fireproof buildings of all types. The design of steel staircases is largely standardized. They consist of a steel string on each side which helps to carry the weight. Iron spiral staircases are usually formed of cast-iron members, each of which forms a tread and a riser. Such spiral staircases are rigid independently of any wall, and are often used in power houses, gymnasiums and so on. Reinforced concrete, sometimes, finished as artificial stone is used for stairs in different forms. e) Moving Staircases In many places where continuous transit between floors is necessary, as in large shops or underground railway stations, moving stars, sometimes called escalators are much used.
