1. Summary Sheet Session Number : Date : Subject Expert : 1 12.03.2007 Dr. 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

2. Learning Outcomes: After this students will be able to do the detailing of staircases through drawing and bar bending schedule.After this students will be able to do the detailing of staircases through drawing and bar bending schedule. DETAILING OF STEEL IN STAIR CASES

3. 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

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

5. Parts of stair a case G T N R W θ Le L1 L2 FLIGHT FIG.1 PARTS OF STAIR CASE Fig. 2 DOG LEGGED STAIR CASE

6. Parts of stairs Flight and landing. Steps Rise-R Going-G=T-N Tread-T Nosing -N G T N R W θ

7. Types 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

8. Straight SC Geometric SC Dog legged SC Transversely spanning SC Some photos

9. Open Well or Newel stair cases I- FLIGHT II- FLIGHT III- FLIGHT LANDING WITH INTERMEDIATE FLIGHTWITHOUT INTERMEDIATE FLIGHT OPEN WELL

10. OTHER STAIRCASES SPIRAL AND GEOMETRIC STAIRCASES RISER AND TREAD STAIRCASE

11. Based on type of span Horizontally spanning or transversely spanning SC Longitudinally spanning SC. For details refer IS:456-2000 and SP-34. CLASSIFICATION

12. Guide 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.

13. Guide lines for fixing the dimensions 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.

14. Design 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.

15. Transversally spanning stair case STEPS STRINGER BEAMS STRINGER BEAM 0.5 A st 0.1Le- 0.15Le LeLe A st D1 D2 STIRRUP MAIN STEEL DIST. STEEL Refer SP-34 for more details

16. MAIN A st 0.5A st DSDS DBDB bWbW L 6φ m LeLe 0.1-0.15L e φm φm DS STAIR CASE SUPPORTED ON SIDE BEAMS-DETAILS STIRRUP DETAILS AND HOOK TRANSVERSLY SPANNING

17. LeLe LANDING WAIST SLAB Case (a) EFFECTIVE SPAN FOR LONGITUDINALLY SPANNING STAIRCASES WALL WAIST SLAB SUPPORTED AT THE ENDS OF LANDINGS

18. EFFECTIVE SPAN FOR LONGITUDINALLY SPANNING STAIRCASES XXYY LeLe Case (c) Case (b) LeLe L e =G +[ X +Y], X ≤1m AND Y ≤1m L e =c/c of beams GOING=G

19. Longitudinally spanning SC Detailing Steel at bottom longitudinally-tension Anchorage and development steel Distribution steel Row of chairs Nominal foundation for ground flight

20. Exercise 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

21. Exercise 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 level Main steel for each flight = #12@120 Distribution steel for each flight = #8@ 200 Use M20 concrete and Fe 415 steel. Draw to a suitable scale The plan of stair case Sectional elevation of the Ground flight Sectional elevation of the First flight Bar bending schedule

22. Solution Dimensioning: R=160 mm, T= 250 mm Floor to floor height = 3200mm No of rises = 3200/R = 20. Each flight has 10 rises. No of treads per flight=10-1 =9 Width of landing along flight = (4480-9x250)/2 = 1115mm. Going of flight=9x250 =2250mm Development length = 47φ= 47 x 12 = 564 mm

23. Exercise Plan of stair case PLAN 1115 mm 2250 mm L e = 4710 mm Gap=0.1m 2100 Clear dimension of stair case room=4.48 m x 2.1 m

24. ROW OF CHAIRS 500 mm GL Wall FOUNDATION GROUND FLIGHT MAIN STEEL # 12 @ 120 DIST. STEEL # 8 @ 200 150 L d =564 REINFORCEMENT FROM BM L d =564 FLOOR 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]

25. PLAN LeLe DETAILING Flight spans longitudinally on landing beams

26. LdLd LdLd T Extra steel if needed Concrete spalling due to tension in steel Wrong ok Details at the junction of flight and landing

27. STRAIGHT STAIR CASE Refer SP-34 and learn the details

28. Member Mark No. of bars Dia. in mm Length in m/piece Total length in m Bar detailsRemarks #12#8 SC GFl A912measureX1 8 spacings, main bar B912measureX2 Main bar CCount8960Y1 Dist. Bar L=1000- 2EC Bar bending schedule For exercise problem

29. Stair- Ground Floor D912measureX3 Anchorage bars E912measureX4 Anchorage 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.,

30. Estimation of quantity of concrete Volume of concrete = L x B x D L= length along the central line in m-measured B=Breadth in m D=Thickness of slab in m Plus concrete in footing Weight of concrete, kg = Volume x density

31. 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.

32. The end Thank you very much Dr. M. C. Nataraja