1. Building Code Requirements for Structural Concrete (ACI 318M-11) Design of Structures with High-Strength Concrete by ACI 318 David Darwin Vietnam Institute for Building Science and Technology (IBST) Hanoi and Ho Chi Minh City December 12-16, 2011

2. This morning Slender columns Walls High-strength concrete

3. Background ACI 318 provisions that apply to high-strength concrete

4. Background High strength concrete = ?

5. 1920s> 20 MPa 1950s> 35 MPa 1990s> 60 MPa

6. > 70 MPa

7. 100 – 135 MPa

8. High-strength concrete Small % Important Columns in high-rise buildings

9. The tallest building in the world is constructed of reinforced concrete

10. Compressive behavior

11. cylinder size 100 x 200 mm vs. 150 x 300 mm molds

12. f' c (4x8 in.) = 1.016f' c (6x12 in.) f' c (100x200 mm) = 1.016f' c (150x300 mm)

13. End condition

15. Stress-strain curves

16. Behavior in compression tests

21. Strength versus age

22. Strength gain - example 28 days 91 days % gain absolute gain 20 MPa 35 MPa 75 % 15 MPa 64 MPa 92 MPa 44 % 28 MPa

23. Tensile and fracture behavior

26. Relationship between tensile and compressive strength

27. Fracture The energy required to open a crack once the tensile strength has been reached

29. Fracture energy vs. compressive strength

30. Structural behavior Bond Shear

31. Bond 1.83 m 4.88 m

32. Splices w/o confining reinforcement

33. Splices w/ confining reinforcement

34. A s f s /f′ c 1/2 (Prediction), in. 2 A s f s /f′ c 1/2 (Test), in. 2

35. A s f s /f′ c 1/4 (Prediction), in. 2 A s f s /f′ c 1/4 (Test), in. 2

36. Shear

37. Creep and shrinkage

38. Specific creep

39. Creep coefficient

40. Shrinkage

41. ACI 318 provisions that apply to high- strength concrete Required average strength Evaluation and acceptance of concrete Stress block parameter Limits that apply to shear, torsion, and bond Transmission of column loads through floor systems

42. Required average strength

43. Evaluation and acceptance of concrete (a)Arithmetic average of all sets of three consecutive strength tests* equals or exceeds (b)No strength test* falls below by more than 3.5 MPa when is 35 MPa or less; or by more than when is more than 35 MPa *Test = average strength of three 100  200 mm cylinders or of two 150  300 mm cylinders

44. Stress-block parameter  1

45. Limits that apply to shear, torsion, and bond Shear and torsion

46. Bond

47. Transmission of column loads through floor systems

50. Summary Background ACI 318 provisions that apply to high-strength concrete

51. 51

52. Figures copyright  2003 by Pearson Education, Inc. Upper Saddle River, NJ USA Figures copyright  2010 by McGraw-Hill Companies, Inc. 1221 Avenue of the America New York, NY 10020 USA Figures copyright  2011 by American Concrete Institute 38800 Country Club Drive Farmington Hills, MI 48331 USA Duplication authorized for use with this presentation only.

53. The University of Kansas David Darwin, Ph.D., P.E. Deane E. Ackers Distinguished Professor Director, Structural Engineering & Materials Laboratory Dept. of Civil, Environmental & Architectural Engineering 2142 Learned Hall Lawrence, Kansas, 66045-7609 (785) 864-3827 Fax: (785) 864-5631 daved@ku.edu