Lecture 35 - Design of Two-Way Floor Slab System

1. Lecture 35 - Design of Two-Way Floor Slab System April 23, 2003 CVEN 444

2. Lecture Goals One-way and two-way slab Slab thickness, h

3. Comparison of One-way and Two-way slab behavior

4. Comparison of One-way and Two-way slab behavior

5. Comparison of One-way and Two-way slab behavior

6. Comparison between a two-way slab verses a one-way slab

7. Comparison of One-way and Two-way slab behavior

8. Comparison of One-way and Two-way slab behavior

9. Comparison of One-way and Two-way slab behavior Economic Choices Flat Plate suitable span 20 to 25 ft with LL= 60 -100 psf Advantages Low cost formwork Exposed flat ceilings Fast Disadvantages Low shear capacity Low Stiffness (notable deflection)

10. Comparison of One-way and Two-way slab behavior Economic Choices Flat Slab suitable span 20 to 30 ft with LL= 80 -150 psf Advantages Low cost formwork Exposed flat ceilings Fast Disadvantages Need more formwork for capital and panels

11. Comparison of One-way and Two-way slab behavior Economic Choices Waffle Slab suitable span 30 to 48 ft with LL= 80 -150 psf Advantages Carries heavy loads Attractive exposed ceilings Fast Disadvantages Formwork with panels is expensive

12. Comparison of One-way and Two-way slab behavior Economic Choices One-way Slab on beams suitable span 10 to 20 ft with LL= 60-100 psf Can be used for larger spans with relatively higher cost and higher deflections One-way joist floor system is suitable span 20 to 30 ft with LL= 80-120 psf Deep ribs, the concrete and steel quantities are relative low Expensive formwork expected.

13. Comparison of One-way and Two-way slab behavior

14. Two-Way Slab Design

15. Two-Way Slab Design

16. Two-Way Slab Design

17. General Design Concepts

18. General Design Concepts

19. Equivalent Frame Method (EFM)

20. Equivalent Frame Method (EFM)

21. Method of Analysis

22. Method of Analysis

23. Method of Analysis

24. Column and Middle Strips

25. Minimum Slab Thickness for two-way construction

26. Minimum Slab Thickness for two-way construction

27. Minimum Slab Thickness for two-way construction

28. Minimum Slab Thickness for two-way construction

29. Minimum Slab Thickness for two-way construction

30. Minimum Slab Thickness for two-way construction

31. Definition of Beam-to-Slab Stiffness Ratio, a

32. Definition of Beam-to-Slab Stiffness Ratio, a

33. Beam and Slab Sections for calculation of a

34. Beam and Slab Sections for calculation of a

35. Beam and Slab Sections for calculation of a

36. Minimum Slab Thickness for two-way construction

37. Example - Slab

38. Example - Slab

39. Example - Slab

40. Example – a calculations

41. Example – a calculations

42. Example – a calculations

43. Example – a calculations

44. Example – a calculations

45. Example – a calculations

46. Example – a calculations

47. Example – a calculations

48. Example – a calculations

49. Example – a calculations

50. Example – a calculations

51. Example – a calculations

52. Example – a calculations