how do you takeoff a staircase?

Summary SheetSession Number

:Date :

Subject Expert :

1 12.03.2007 Dr. M.C. NatarajaDr. M.C. Nataraja

Professor

Department of Civil Engineering,

Sri Jayachamarajendra College of Engineering,

Mysore – 570 006.

Phone:0821-2343521, 9880447742

E-mail: nataraja96@yahoo.com

Learning Outcomes:

• After this students will be able to do the detailing of After this students will be able to do the detailing of staircases through drawing and bar bending staircases through drawing and bar bending schedule. schedule.

DETAILING OF STEEL IN STAIR CASES

Contents• Definition and parts of Stair cases• Types of stair cases• Requirements• Detailing principles• Problems• Art of Drawing• Bar bending schedule

Detailing of steel in Stair cases

STAIR CASE

Definition

Stair cases are used for the purpose of giving access to different floors of a structure.

Parts of stair a caseParts of stair a case

G

T

N

R

W

θ

Le

L1L2

FLIGHT

FIG.1 PARTS OF STAIR CASEFig. 2 DOG LEGGED STAIR CASE

Parts of stairsParts of stairs

Flight and landing.

StepsRise-RGoing-G=T-NTread-TNosing -N

G

T

NR

W

θ

Types of stair casesTypes of stair cases

Based on shape

• Straight stairs• Dog legged stairs• Open well or open newel stairs• Geometrical stairs such as spiral, circular, etc.• Free standing stair cases

Straight SC

Geometric SC

Dog legged SC

Transversely spanning SC

Some photos

Open Well or Newel stair casesOpen Well or Newel stair cases

I- FLIGHT

II- FLIGHT

III- FLIGHT

LANDING

WITH INTERMEDIATE FLIGHT WITHOUT INTERMEDIATE FLIGHT

OPEN WELL OPEN

WELL

OTHER STAIRCASESOTHER STAIRCASES

SPIRAL AND GEOMETRIC STAIRCASES RISER AND TREAD STAIRCASE

Based on type of spanBased on type of span

• Horizontally spanning or transversely

spanning SC

• Longitudinally spanning SC.

For details refer IS:456-2000 and SP-34.

CLASSIFICATION

Guide lines for fixing the dimensionsGuide lines for fixing the dimensions

Rise (R) : 150mm to 180mm Tread (T) : 220 mm to 250 mm- for residential buildings.

Rise (R) : 120 to 150 mm Tread (T) : 250 mm to 300 mm – for public buildings

[T + 2R] : Between 500 mm to 650 mm

The width of the stair• 0.8 m to 1 m for residential building and • 1.8 m to 2 m for public building.

Guide lines for fixing the dimensions Guide lines for fixing the dimensions Contd…Contd…

• The width of the landing is equal to the width of stairs.

• The number of steps in each flight should not be greater

than 12

• The pitch of the stair should not be more than 38 degrees.

• The head room measured vertically above any step or

below the mid landing shall not be less than 2.1 m.

Design of stairsDesign of stairs

Design for maximum bending moment and check for maximum shear force.

The depth is to be fixed from deflection criteria.

Stair case slab is designed as a conventional slab.

All rules regarding the detailing are similar to that of slab.

Enough development and anchorage lengths for steel should be provided.

Transversally spanning stair caseTransversally spanning stair case

STEPS

STRINGER BEAMS STRINGER

BEAM

0.5 Ast

0.1Le-0.15Le

Le

Ast

D1 D2

STIRRUP

MAIN STEEL

DIST. STEEL

Refer SP-34 for more details

MAIN Ast

0.5Ast

DS

DB

bW

L

6φm

Le

0.1-0.15Le

φm

DS

STAIR CASE SUPPORTED ON SIDE BEAMS-DETAILS

STIRRUP DETAILS AND HOOK

TRANSVERSLY SPANNING

Le

LANDING

WAIST SLAB

Case (a)

EFFECTIVE SPAN FOR LONGITUDINALLY

SPANNING STAIRCASES

WALL

WAIST SLAB SUPPORTED AT THE ENDS OF LANDINGS

EFFECTIVE SPAN FOR

LONGITUDINALLY

SPANNING STAIRCASES

X X Y Y

Le

Case (c)

Case (b)

Le

Le=G +[ X +Y], X ≤1m AND Y ≤1m

Le=c/c of beams

GOING=G

Longitudinally spanning SCLongitudinally spanning SC

DetailingDetailing

• Steel at bottom longitudinally-tension

• Anchorage and development steel

• Distribution steel

• Row of chairs

• Nominal foundation for ground flight

ExerciseExercise

A dog legged stair case is to be detailed with the

following particulars:

Clear dimension of stair case room=4.48 m x 2.1 m

The floor to floor height is 3.2 m

Width of each tread =250 mm

Width of each rise = 160 mm

Thickness of waist slab = 150 mm

Width of flight =1m

All round wall = 230 mm

Exercise Exercise contd.,contd.,

Both flights are supported at the ends of landing on 230 mm wall.(Landing and flight spans in the same direction)The first flight starts from the plinth levelMain steel for each flight = #12@120 Distribution steel for each flight = #8@ 200Use M20 concrete and Fe 415 steel.

Draw to a suitable scaleThe plan of stair caseSectional elevation of the Ground flightSectional elevation of the First flightBar bending schedule

SolutionSolution

Dimensioning: R=160 mm, T= 250 mmFloor to floor height = 3200mmNo of rises = 3200/R = 20. Each flight has 10 rises.No of treads per flight=10-1 =9Width of landing along flight

= (4480-9x250)/2 = 1115mm.Going of flight=9x250 =2250mmDevelopment length = 47φ= 47 x 12 = 564 mm

ExerciseExercise

Plan of stair case

PLAN

1115 mm 1115 mm2250 mm

Le = 4710 mm

Gap=0.1m 2100

Clear dimension of stair case room=4.48 m x 2.1 m

ROW OF CHAIRS

500 mm

500 mm

GL

Wall

FOUNDATION

GROUND FLIGHT

MAIN STEEL# 12 @ 120

DIST. STEEL# 8 @ 200

150

Ld =564

REINFORCEMENTFROM BM

Ld =564FLOOR LEVEL

LANDING FIRST FLIGHT

R=160

T= 250

LAP L

DETAILING

Landing and flight spans longitudinally

[A]

[C]

[D,E]-Anchorage steel

Main steel [B]

Y=0.3 l or Ld

LANDING BEAM

500

500

GL

FOOTING

GROUND FLIGHT

FIRST FLIGHT

MAIN STEEL # 12 @ 120

DIST. STEEL # 8 @ 150

LANDING BEAM

150

X

l

Y

Y

150

INTERMEDIATELANDING

ROW OF CHAIRS

X = 0.15 l or Ld

MAIN STEEL

DS

150

PLANLe

DETAILING

Flight spans longitudinally on landing beams

Ld

Ld

T

Extra steel if needed

Concrete spalling due to tension in steel

Wrong

ok

Details at the junction of flight and landingDetails at the junction of flight and landing

STRAIGHT STAIR CASESTRAIGHT STAIR CASE

Refer SP-34 and learn the details

Member MarkNo. of bars

Dia.in

mm

Lengthin

m/piece

Total length in m

Bar details Remarks

#12 #8

SCGFl

A 9 12 measure X18

spacings, main bar

B 9 12 measure X2 Main bar

C Count 8 960 Y1Dist. BarL=1000-

2EC

Bar bending scheduleFor exercise problem

Stair-Ground

Floor

D 9 12 measure X3Anchorage

bars

E 9 12 measure X4Anchorage

bars

Total length in m/diameter - -Calculations are based on

actual measurement on drawing sheet.

Weight in kg/m -- --

Total weight in kg/diameter --- ---

Bar bending schedule-Contd.,

Estimation of quantity of concrete

Volume of concrete = L x B x D

L= length along the central line in m-measuredB=Breadth in mD=Thickness of slab in m

Plus concrete in footing

Weight of concrete, kg = Volume x density

Conclusion

Students have learnt the following:

• Types of staircases.

• Effective span concept.

• Requirements of staircase.

• Detailing of steel.

• Importance of development length and anchorages.

• Drawing to scale and bar bending schedule.

The end

Thank you very much

Dr. M. C. Nataraja