R.C.C. STAIRS...

1. 3. R.C.C. STAIRS
• Reinforced concrete is perhaps the most suitable of all the said
materials for the construction of stairs.
• The various advantages of reinforced concrete stairs are given below
- They have requisite fire resisting qualities to a great extent
- They are durable strong pleasing in appearance and can beThey are durable, strong, pleasing in appearance and can be
easily rendered non-slippery.
- They can be designed for greater widths, longer spans and any
heightheight.
- They can be moulded in any desired form to suit the
requirements of the architect.
Th b il l d- They can be easily cleaned.
- The cost of maintenance is almost nil.
- They can be pre-cast or cast-in-situ.y p
- To change their appearance, R.C.C. stairs can be
covered/finished with thin slabs of stone, marble tiles or terrazzo
finish.

2. DESIGN PRINCIPLE AND SUPPORT SYSTEM:DESIGN PRINCIPLE AND SUPPORT SYSTEM:
• The choice of the type of stair to be adopted depends very much upon
the size of the staircase hall and the loading conditionthe size of the staircase hall and the loading condition.
• DIFFERENT STAIR ARRANGEMENT IN CASE OF R.C.C.
• Single Straight Flight Stairs
• Inclined Slab Stairs With Half Space Landings
• String Beam Stairs
• Crancked Slab Stairs• Crancked Slab Stairs
• Cantilever Stairs
• Spiral Stairsp

3. SINGLE STRAIGHT FLIGHT STAIRS:
• Although simple in
design and
construction is notconstruction, is not
popular because of
the plan space it
occupiesoccupies
• The flight behaves
as simply supported
slab, spanning from
landing to landing.
• The effective span/total horizontal going is usually taken as landing
d d b idi d d d b h l diedge to edge by providing a down stand edge beam to each landing.
• If these edge beams are not provided, the effective span would betaken
as overall of the landings, resulting in a considerably increased
bending moment and hence more reinforcement.

4. INCLINED SLAB STAIRS WITH
HALF SPACE LANDINGS:S C N NGS:
(STAIR WITH SLAB SPANNING
LONGITUDINALLY)
• This type of stairs gives more
compact plan layout and better
i l i h h i l i hcirculation than the single straight
flight stairs.
• The half space or 180o turn landingp g
is introduced at the midpoint of the
total rise, giving equal flight spans,
thus reducing the effective span andthus reducing the effective span and
hence reducing bending moment
considerably.
I t d i th l di• In most designs, the landings span
crosswise on to a load bearing wall
or beam and the flights span from
landing to landing.

5. • The point of intersection of the
soffits to the flights with the
landing soffits can be detailed
in any of two ways:y y
1) INTERSECTION OF SOFFITS
IN LINE, BUT NOSINGS OUTIN LINE, BUT NOSINGS OUT
OF LINE IN THE PLAN:
2) INTERSECTION OF FLIGHTS2) INTERSECTION OF FLIGHTS
AND LANDING SOFFITS ARE
OUT OF LINE ON THE
UNDERSIDE BUT THEUNDERSIDE, BUT THE
NOSINGS IN LINE ON PLAN
• i.e. first and last riser in
i fli h i liconsecutive flights in line on

6. 1) INTERSECTION OF SOFFITS IN LINE, BUT NOSINGS
OUT OF LINE IN THE PLAN:
i.e. first and last riser in the consecutive flights are not in line

7. 2) INTERSECTION OF FLIGHTS AND LANDING SOFFITS
ARE OUT OF LINE ON THE UNDERSIDE BUT THEARE OUT OF LINE ON THE UNDERSIDE, BUT THE
NOSINGS IN LINE ON PLAN
i.e. first and last riser in consecutive flights are in line

8. STRING BEAM STAIRS:
(STAIR WITH SLAB SPANNING HORIZONTALLY)
• In this category, the slab is
supported on one side by side wall
or stringer beam and on the otheror stringer beam and on the other
side by a stringer beam
• I.e. a string or edge beam is used
to span from landing to landing toto span from landing to landing to
resist bending moment with the
steps spanning horizontally.
I thi th i t l b i• In this case, the waist slab is
thinner and an overall saving in
the concrete volume required can
be achieved but this saving inbe achieved, but this saving in
material is usually offset by the
extra formwork cost required for
string beamstring beam.
• The string beam can be either up
stand or down stand in format and
can be on both sides if stairs arecan be on both sides if stairs are
free standing.

9. • Each step is designed as
spanning horizontally with thespanning horizontally with the
bending moment equal to wll/8,
where w is the uniformly
distributed load per unit area ondistributed load per unit area on
the step, inclusive of the self
weight.
• Sometimes, for wider steps, a
central string beam spanning
between the end walls or
column is provided on which
the stairs slab is supported.
• The waist slab is designed as• The waist slab is designed as
slab cantilevering from both the
sides of the string beam

10. CRANCKED SLAB STAIRS:
• These stairs are
very often used as avery often used as a
special feature since
the half space
l di hlanding has no
visible support
being designed as a
cantilever slab.
• Bending, Buckling and torsion stresses are induced with this form of
design creating the need for the reinforcement to both faces of the
landing and the waist slablanding and the waist slab.
• Hence the amount of reinforcement required is high which can
sometimes create site problem with regards to placing and compacting
th tthe concrete.

11. CANTILEVER STAIRS:
• They are also called
spine wall stairs.p
• They consist of a central
vertical wall from which
the flights and halfthe flights and half
space landings are
cantilevered.
Th ll id d f fi i t b t th fli ht d i• The wall provides a degree of fire resistance between the flights and is
therefore used mainly for the escape stairs.
• Since both flights and landings are cantilevered the reinforcement is placed
in the top of the flight slab and in the upper surface of the landing to
counteract the induced negative moment.
• The plan arrangement can be a single straight flight or two flights with half• The plan arrangement can be a single straight flight or two flights with half
space landings.

12. R.C.C.SPIRAL AND HELICAL STAIRS
• Mainly used as accommodation
stairs in the foyers of prestige
buildings such as theatres, banks,buildings such as theatres, banks,
commercial complexes etc.
• Can be expensive to construct-
normally at least seven times thenormally at least seven times the
cost of conventional stairs.
• The plan shape is generally based on
a circle; it is also possible to designa circle; it is also possible to design
an open spiral stair with an elliptical
core, which is known as helical
stairsstairs.
• The spiral an be designed around a
central large diameter circular
column where the steps arecolumn, where the steps are
cantilevered from that, or in case of
helical stairs, can be designed as
open circular well.open circular well.

13. • A large amount of steel
reinforcement is used to resist the
bending moment, shear force and
torsional moment.
• The continuous slab varies in
thickness from top to bottom- less
at top and increasing at the bottomat top and increasing at the bottom.
• There are two or three sets of
reinforcement with top and bottom
layer in each:
– Continuous bars running the
length of the spirale gt o t e sp a
– Cross or radial bars
– Diagonal bars laid tangential in
two directions to the inner
curve.

21. Th k YThank You