Lecture 16 DesignT-Beams

1. Lecture 16 � Design(T-Beams) February 21, 2003 CVEN 444

2. Lecture Goals Design of T-Beams Known section dimensions

3. Design Procedure for section dimensions are unknown (T- Reinforced Beams)

4. Design Procedure for Singly Reinforced Flange Beams when flange is in compression Known dimensions Calculate controlling value for the design moment, Mu. Assume that resulting section will be tension controlled, et 0.005 so that can take f = 0.9.

5. Design Procedure for Singly Reinforced Flange Beams when flange is in compression Known dimensions Calculate d, since h is known

6. Design Procedure for Singly Reinforced Flange Beams when flange is in compression Known dimensions Determine the effective width of the flange, beff Check whether the required nominal moment capacity can be provided with compression in the flange alone. and

7. Design Procedure for Singly Reinforced Flange Beams when flange is in compression Known dimensions If Need to utilize web below flanges. Go to step 4. If Use design procedure for rectangular beams with b = beff , (d -a/2) = 0.95d Note: f = 0.9 for flexure without axial load (ACI 318-02 Sec. 9.3)

8. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Find nominal moment capacity provided by overhanging flanges alone (not including web width) For a T shaped section: and

9. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Find nominal moment capacity that must be provided by the web.

10. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Calculate depth of the compression block, by solving the following equation for a.

11. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Find required reinforcement area, As (req�d)

12. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Select reinforcing bars so As (provided) As (req�d). Confirm that the bars will fit within the cross-section. It may be necessary to change bar sizes to fit the steel in one layer or even to go to two layers of steel.

13. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Calculate the actual Mn for the section dimensions and reinforcement selected. Check strength f Mn Mu (keep over-design within 10 %)

14. Singly Reinforced Beams where flange is in compression Design Procedure when section dimensions are known Check whether As provided is within allowable limits. As (provided) As (min)

15. Minimum Area

16. Additional Requirements for flanged sections when flange is in tension

17. Additional Requirements for flanged sections when flange is in tension

18. Additional Requirements for flanged sections when flange is in tension

19. Design Procedure for SR Beam Unknown Dimension

20. Design Procedure for SR Beam Unknown Dimension

21. Example Problem

22. Example Problem

23. Example Problem � Negative Moment

24. Example Problem-b Value

25. Example Problem � k value

26. Example Problem � Design

27. Example Problem � Design

28. Example Problem � Design

29. Example Problem � Design

30. Example Problem � Design

31. Example Problem � Check

32. Example Problem � Check

33. Example Problem � Check

34. Example Problem � Flange

35. Example Problem � Flange

36. Example Problem � Flange

37. Example Problem � Flange

38. Example Problem � Steel

39. Example Problem � Cover

40. Example Problem � a value

41. Example Problem � Strain

42. Example Problem � Mn

43. Example Problem � Amin

44. Example Problem � Summary

45. Example Problem � Positive Moment

46. Example Problem � Capacity

47. Example Problem � Amin

48. Example Problem � a value

49. Example Problem � Mn

50. Example Problem � Summary

51. Homework