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ON

DESIGN OF STAIRCASE

                                            INTRODUCTIONFloors situated at different levels are connected, for communication, by any of the following methods.

(1)Ladders.                                                                                                                               (2)  Steps-stairs.(3)  Escalators.(4)  Lifts.(5)Rampsandchuts.                                                                              (6)  Trolley-rope-ways.

(1)  Ladders: These are made of two side support, called up rights, either of wood, bamboo, mild steel, cast iron      or pipes spaced with horizontal rugs. These can be portable or fixed as the need be. Wooden rungs held into      twisted upright ropes are also very light ladders; these are mainly used in ships, boats and sea-trailers etc.      Such ladders are also used for painting white washing in tall buildings.

(2)  Steps: Steps made in the form of a series of rising footing is termed as stair. A couple of steps built in series      is known as a flight. Stair can be made into many shapes and designs out of any building-material.

(3)  Escalators: These are steps fixed on very slow moving belts. These are called moving stairs. These help in      reducing the climbing time of stairs and are used at public places having vary high intensity of public      movement. Like bus terminals, railway stations air ports etc.

(4)  Lifts: These are ventilated encased chambers which can be moved up and down in a shaft connecting      different floors of a structure. These are high and low speed lifts. Lifts are electrically operated. Certain      towers and sky-scrapers have lifts operating on outer faces of the structures. They are fixed with plexiglass     and give the users a better view of the outside scenery around.

(5) Ramps and chuts: These are solid or inclined laid slabs between two floors situated at different levels. The     normal gradients are 1 in 20 to 1 in 50. These are used in hospitals, multistoreyed parking area. swimming     pools and children parks also have ramps, which are used for recreational purposes.

(6) Trolley-rope-ways: Trolleys made in the form of cabs are held on guy ropes and operated up and down     between two different levels. These are mainly installed to connect two banks of a deep valley.

2.     Tread:    The horizontal member which forms the upper surface of a step is called tread.3.     Riser:    It is the vertical front portion of a step.4.     Rise:    It is the vertical distance between the two upper surfaces of two successive steps.5.     Nosing:    The front edge of a tread is termed as nosing.6.     Line of nosing:    Imaginery line joining the nosings and parallel to the slope of stair is        termed as line of nosing.7.     Flier:    A regular and rectangular step is known as flier.8.     Flight:    A series of continuous steps between two floors, or floor to landing or landing to landing is helps        in turning of stair.9.     Landing:    This is a horizontal platform which is provided between two flights to serve as a rest. It also        helps in turning of stair.10.   Slope or Pitch:    The angle between the line of nosing and floor is known as slope.11.   Strings and stringers:    These are inclined members which support the steps. The strings may be provided        on each of a step or in the centre to support steps as cantilever extending on each side.12.   Soffit or plancer:    Under surface of a flight is called soffit.13.   Balusters:    Vertical members which support the hand rail are known as balusters.14.   Hand rails:    Hand rails are provided on top of balusters. It safe guard's the persons using the stairs. Hand         rails may be made of wood, masonry, R.C.C. or synthetic materials. It can be fixed even to the walls of        staircase.15.   Head room:    The vertical distance between the line of nosings and the soffit or landing of a flight         immediately above it is known as head-room. Head-room should not be less than 2.20 meters. 

STAIRS

Technical Terms:1.     Stair:    Steps arranged in a series for communicating between two floors is known as a stair. 

LOCATION OF STAIR

Stair should be placed at a central place in the building so as to give shortest access to all rooms. It should be well ventilated and airy.TYPES OF STAIRS

Following are different forms of stairs1. Straight flight on solid spandril filling.        (a) Straight flight on solid spandril filling.        (b) Straight flight on hollow-arched or lintelled opening spandril.        (c) Straight flight on inclined R.C.C. slab.        (d) Straight flight on two-side-strings.        (e) Straight flight on central-single string.        (f) Straight flight stair made of cantilever steps projecting from a wall.2. Dog-legged stairs. 3. Open well stairs or open newel stairs.4. Newel stairs. 5. Geometrical stairs.6. Circular stairs.7. Spiral stairs.8. Bifurcated stairs.

These stairs can be made out of masonry, wood, composite masonry, R.C.C., steel and alloys or synthetic materials. Stairs from serial 2 to 8 can also be built on stringers-beams.

PRINCIPLES TO BE OBSERVED WHILE PLANNING AND DESIGNING A STAIR

1.  Width of Stair: It should not be less than 1.00m.2.  Length of flight: The number of steps in a single flight should not be more than 12.3.  Pitch of the stair: It should be between 25o to 40o4.  Width of landing: It should be 150mm, more than the width of stair.5.  Winders or kite steps: Odd shaped steps should be avoided and incase found necessary. These should be     provided at the start of a stair.6.  Han-rails: It should be 750 to 850 mm in height from the top of respective step or landing.7.  Step proportions: The size of rise and tread in a stair should be kept uniform through out the whole stair.

Following proportions are recommended:

(i)  Residential buildings-Tread=250 mm                                        Rise=160 mm

(ii)  Public buildings - Tread=300 mm                                    Rise=150 mm

(iii) Industrial buildings, Railway station,                                   etc tread=not less then 250 mm                                   =250 to 300 mm                                   Rise=not less then 150 mm                                   =150 to 190 mm

Otherwise work out the sizes of rise and tread by using any one of the following proportions

(i)   (2xRise)+(Going), In mm=550 to 600 mm(ii)  Rise x tread, both in cm = 400 to 410 cm2.(iii) With basic proportion of going 300 mm and rise 150 mm, add 10 mm to rise for every 20 mm deduction     from going e.g. For a going of 280 mm the rise will be 160 mm. The above rules act as guide but the actual sizes depend upon the availability of space, while planning stairs practical-field.

THANKSA

LOT