In this article, we will explain the step-by-step design process for creating the design of a waist slab type staircase along with reinforcement detailing.
Tread – Stair tread is the horizontal portion of a set of stairs on which a person walks. The tread can be composed of wood, metal, plastic, or other materials. In residential settings, treads can be covered in carpeting. Stair treads can come in non-slip varieties, particularly in commercial or industrial locations. The dimension varies from 270 mm for residential buildings and factories and 300 mm for public buildings where huge number of persons utilize the staircase.
Riser: The vertical distance amid two consecutive steps is known as riser. The dimension of the riser differs from 150 mm for public buildings and 190 mm for residential buildings and factories.
Waist: The depth of the waist-slab on which steps are built up is called as waist. The depth (thickness) of the waist is the least thickness perpendicular to the soffit of the staircase (cl. 33.3 of IS 456). The steps of the staircase which stand on waist-slab can be developed with bricks or concrete.
General guidelines for making the plan for a staircase:
• The relevant dimensions of tread and riser for all the parallel steps should be identical in sequential floor of a building.
• The minimum vertical headroom over any step should remain at 2 m.
• Usually, the number of risers in a flight should be limited to twelve.
• The lowest width of stair should have been 850 mm, though it is recommended to keep the width among 1.1 to 1.6 m. In public building, cinema halls etc., large widths of the stair should be arranged.
The solution is given to the following problem in video tutorial:-
Design one of the flights of stairs (waist slab type) concerning a school building that extents among beams on the basis of following data :-
Number of steps in flight = 12
Tread (T) =300 mm
Riser (R) = 160 mm
Width of landing beam = 400 mm
Components = M20 grade concrete and fe 415 HYSD bar
Effective Span (L) is calculated as follow :-
L = 12 x 300 + 400 = 4000 mm
L = [(no. of steps in flight x tread) + width of landing beam]
Thickness of waist slab = span /20 = 4000/20 = 200 mm
Watch the video: