What is the effective span of staircase supported at each end by edge of the landing slab, which spans parallel, with the risers, if width of both landings is 2.5 m and going of stair is 2.2 m (see fig):
What is the effective span of staircase supported at each end by edge of the landing slab, which spans parallel, with the risers, if width of both landings is 2.5 m and going of stair is 2.2 m (see fig): Correct Answer 4.2
Concept:
Clause 33.1 of IS 456:2000 gives us the guideline to calculate the effective span of a stair 'where spanning on to the edge of a landing slab, which spans parallel, with the risers, a distance equal to the going of the stairs plus at each end either half the width of the landing or one meter, whichever is smaller.'
Calculation:
Given:
Going of stair = 2.2 m
half width of landing = 2.5 / 2 = 1.25 m > 1 m
∴ adopted legth for calculation of effective span = 1 m
∴ Effective span of stair = 2.2 + 1 + 1 = 4 m
Important Points
Some frequent stair types and their effective spans are given below
|
Span type |
Effective Span |
|
Where supported at top and bottom risers by beams spanning parallel with the risers |
The distance center-to-center of beams. |
|
Where spanning on to the edge of a landing slab, which spans parallel, with the risers |
A distance equal to the going of the stairs plus at each end either half the width of the landing or one metre, whichever is smaller |
|
Where the landing slab spans in the same direction as the stairs, they shall be considered as acting together to form a single slab. |
The span determined as the distance centre-to-centre of the supporting beams or walls, the going being measured horizontally. |
