RCC · staircase
Dog-legged staircase
1
Stair and design mode
IS 456 cl 33.1
Design mode
Support — cl 33.1
Waist — searched
waist searched · every mat designedthe flight and its landings span as one slab
IS 456 prints no moment for a stair. A member whose two ends bear on beams cast with it takes w l²/10 — the practice’s allowance for their partial fixity, not a clause. A member with either end on a wall, or on a landing slab, takes the statics w l²/8. The waist is searched from 100 to 300 mm.
2
Geometry
the architect's — taken as entered
R = 160.0 mm · going 2.700 mhall 5.100 × 2.500 m
3
Landings and supports
cl 33.1 · cl 33.2
At the floor landing's outer edge
At the mid landing's outer edge
Flight edges built ≥ 110 mm into a wall — cl 33.2
span 5.330 m — cl 33.1 (c)between two beams · w l²/10
4
Loads
IS 875 (Part 2) Table 1 · on plan
Occupancy
flight 13.33 · factored 20.00 kN/m²imposed 3.00 kN/m²
5
Materials and cover
Tables 3, 5, 16
Grade of concrete
Grade of steel
Exposure
Moderate needs M 25 — M 25 clears itcover 30 mm
6
Reinforcement
the smallest placeable size
Main bar sizes permitted
flight 12 Ø @ 130 · dist 8 Ø @ 150no bar thicker than an eighth of the waist — cl 26.5.2.2
A flight meets each landing in two corners. The soffit turns re-entrant at the flight’s head and the top face at its foot, and a tension bar is never bent round either — IS 456 cl 26.2.2.6. The bars there are crossed, each carried past the crossing by its development length at least (SP 34:1987 cl 10.8); in (c) and (b) a top bar bends at the foot only past the point of inflection, where it is in compression.