R.C.C. STAIRS

R.C.C. STAIRS...

1. 3. R.C.C. STAIRS
• Reinforced concrete is perhaps the most suitable of all the said
materialsfortheconstructionofstairs.
• Thevariousadvanta
g
esofreinforce
d
concretestairsare
g
iven
b
elow
- Theyhaverequisitefireresistingqualitiestoagreatextent
-
They
are
durable
strong
pleasing
in
appearance
and
can
be
They
are
durable
,
strong
,
pleasing
in
appearance
and
can
be
easilyrenderednon-slippery.
- They can be designed for greater widths, longer spans and any
height height
.
- They can be moulded in any desired form to suit the
requirementsofthearchitect. Th
b
il
ld
-
Th
e
y
can
b
eeas
ily
c
l
eane
d
.
- Thecostofmaintenanceisalmostnil.
-The
y
can
b
e
p
re-casto
r
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. DESIGNPRINCIPLEANDSUPPORTSYSTEM: DESIGN
PRINCIPLE
AND

SUPPORT

SYSTEM:
• The choice of the type of stair to be adopted depends very much upon
thesizeofthestaircasehallandtheloadingcondition the
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 Landin
g
s
• String Beam Stairs
•
CranckedSlabStairs
•
Crancked
Slab
Stairs
• Cantilever Stairs •S
p
iral Stairs
p

3. SINGLE STRAIGHT FLIGHT STAIRS:
• Although simple in
design and
construction
is
not
construction
,
is
not
popular because of the plan space it occupies occupies
• The flight behaves
as simply supported
slab, spannin
g
from
landingtolanding.
• The effective span/total horizontal going is usually taken as landing
d
d
b
idi
d
d
d
b
h
ldi
e
dg
etoe
dg
e
by
p
rov
idi
n
g
a
d
ownstan
d
e
dg
e
b
eamtoeac
h
l
an
di
n
g
.
• Iftheseedgebeamsarenotprovided,theeffectivespanwouldbetaken
as overall of the landings, resulting in a considerably increased
b
endin
g
momentan
d
hencemorereinforcement.

4. INCLINED SLAB STAIRS WITH
HALF
S
PA
C
E LA
N
DI
NGS:
SC NNGS:
(STAIR WITH SLAB SPANNING
LONGITUDINALLY)
• This type of stairs gives more
compact plan layout and better
ili
h
h
il
ih
c
i
rcu
l
at
i
on t
h
an t
h
es
i
n
gl
estra
igh
t
flightstairs.
• The halfs
p
ace o
r
180o turn landin
g
p
g
is introduced at the midpoint of the
total rise, giving equal flight spans,
thus
reducing
the
effective
span
and
thus
reducing
the
effective
span
and
hence reducing bending moment considerably. I
t
di
th
ldi
•
I
nmos
t
d
es
ig
ns,
th
e
l
an
di
n
g
sspan
crosswise on to a load bearing wall
or beam and the flights span from
landin
g
tolandin
g
.

5. • The point of intersection of the
soffits to the fli
g
hts with the
landing soffits can be detailed
inan
y
oftwowa
y
s:
y
y
1) INTERSECTION OF SOFFITS
IN
LINE,
BUT
NOSINGS
OUT
IN
LINE,
BUT
NOSINGS
OUT
OFLINE IN THE PLAN:
2
)
INTERSECTION
OF
FLIGHTS
2
)
INTERSECTION
OF
FLIGHTS
AND LANDING SOFFITS ARE OUTOFLINEONTHE UNDERSIDE
BUT
THE
UNDERSIDE
,
BUT
THE
NOSINGSIN LINE ON PLAN
• i.e. first and last riser in
i
fli h
i
li
consecut
i
ve
fligh
ts
i
n
li
neon

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
AREOUTOFLINEONTHEUNDERSIDE BUTTHE ARE

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
supportedononesidebysidewall
or
stringer
beam
and
on
the
other
or
stringer
beam
and
on
the
other
sidebyastringerbeam
• I.e. a string or edge beam is used
to
span
from
landing
to
landing
to
to
span
from
landing
to
landing
to
resist bending moment with the
stepsspanninghorizontally.
I
thi
th
it
lb
i
•
I
n
thi
s case,
th
ewa
i
s
t
s
l
a
b
i
s
thinner and an overall saving in
the concrete volume required can
be
achieved
but
this
saving
in
be
achieved
,
but
this
saving
in
material is usually offset by the extra formwork cost required for string
beam
string
beam
.
• The string beam can be either up
stand or down stand in format and
can
be
on
both
sides
if
stairs
are
can
be
on
both
sides
if
stairs
are
freestanding.

9. • Each step is designed as
spanning
horizontally
with
the
spanning
horizontally
with
the
bending moment equal to wll/8,
where w is the uniformly
distributed
load
per
unit
area
on
distributed
load
per
unit
area
on
the step, inclusive of the self weight.
• Sometimes, fo
r
wide
r
steps,
a
central string beam spanning b
etween the en
d
walls o
r
column is provided on which thestairsslabissupported.
•
The
waist
slab
is
designed
as
•
The
waist
slab
is
designed
as
slab cantilevering from both the sidesofthestringbeam

10. CRANCKED SLAB STAIRS:
• These stairs are
very
often
used
as
a
very
often
used
as
a
specialfeaturesince
the half space
ldi
h
l
an
di
n
g
h
as no
visible support
being designed as a
cantileve
r
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
slab
landing
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
t
th
econcre
t
e.

11. CANTILEVER STAIRS
:
• They are also called
s
p
inewallstairs.
p
• They consistof a central
vertical wall from which
the
flights
and
half
the
flights
and
half
space landings are cantilevered.
Th
ll
id
d
f
fi
it
bt
th
fli ht
d
i
•
Th
ewa
ll
p
rov
id
es a
d
e
g
ree o
f
fi
re res
i
s
t
ance
b
e
t
ween
th
e
flight
san
d
i
s
thereforeusedmainlyfortheescapestairs.
• 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
counteracttheinducednegativemoment. •
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
spacelandings.

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,
commercialcomplexesetc.
• Can be expensive to construct-
normally
at
least
seven
times
the
normally
at
least
seven
times
the
costofconventionalstairs.
• Theplanshapeisgenerallybasedon
a
circle
;
it
is
also
possible
to
design
a
circle
;
it
is
also
possible
to
design
an open spiral stair with an elliptical
core, which is known as helical
stairs stairs
.
• The spiral an be designed around a
central large diameter circular
column
where
the
steps
are
column
,
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 use
d
to resist the
bending moment, shear force and
torsionalmoment.
• The continuous slab varies in
thickness from top to bottom- less
at
top
and
increasing
at
the
bottom
at
top
and
increasing
at
the
bottom
.
• There are two or three sets of
reinforcement with top and bottom
la
y
e
r
ineach:
– Continuous bars running the
l
e
n
gt
h
o
f
t
h
e
sp
ir
a
l
egt
o
te
sp a
– Crossorradialbars
– Diagonalbarslaidtangentialin
two directions to the inne
r
curve.

21. Th kY Th
an
k
Y
ou