Day03_TanksDay03Day03Day03Day03Day0.pptx

Day03

1. صدق الله العظيم بســـم الله الرحمن الرحيـــم {و اتَّقُواْ اللَّهَ وَ يُعَلَّمُكُمُ اللَّهُ, وَ اللَّهُ بكُلَّ شَئْ عَليمٌ} 1

2. 3. Design of liquid retaining structures Prepared by: Dr.- Khaled Mohamed Hilal Associate Professor, Structural Eng. Department Ain Shams University AIN SHAMS UNIVERSITY FACULTY OF ENGINEERING Structural Engineering Department 2

3. Outline Types of Tanks Special design requirements Rectangular tanks Cylindrical tanks Surfaces of revolution 3

4. Introduction Storage tanks are built for storing water, liquid petroleum, petroleum products and similar liquids Designed as crack free structures to eliminate any leakage Permeability of concrete is directly proportional to water cement ratio. Cement content ranging from 330 Kg/m 3 to 530 Kg/m 3 is recommended in order to keep shrinkage low. 4

5. Introduction Use of high strength deformed bars are recommended for the construction of liquid retaining structures Correct placing of reinforcement, use of small sized and use of deformed bars lead to a diffused distribution of cracks A crack width of 0.1mm has been accepted as permissible value in liquid retaining structures 5

6. Introduction In order to minimize cracking due to shrinkage and temperature, minimum reinforcement is recommended as: For thickness  100 mm = 0.3 % For thickness  450 mm = 0.2% For thickness between 100 mm to 450 mm = varies linearly from 0.3% to 0.2% For concrete thickness  225 mm, two layers of reinforcement be placed, one near water face and other away from water face. 6

7. Types of Water Tanks WATER TANK BASED ON PLACEMENT OF TANK BASED ON SHAPE OF TANK 1. RESTING ON GROUND 2. UNDER GROUND 3. ELEVATED 1. CIRCULAR 2. RECTANGULAR 3. SPHERICAL 4. INTZ 5. CONICAL BOTTOM 7

8. Types of Water Tanks RESTING ON GROUND 8

9. Types of Water Tanks UNDERGROUND 9

10. Types of Water Tanks ELEVATED 10

11. Types of Water Tanks Rectangular Cylindrical 11

12. Types of Water Tanks SPHERICAL INTZ 12

13. Types of Water Tanks CONICAL BOTTOM 13

14. Code Requirements - EC 14

15. Code Requirements - EC 15

16. Code Requirements - EC 16

17. Crack Control – Theoretical Background Load induced cracks: Cracks are caused by tensile stresses due to loads moments, shears, etc.. 17

18. Crack Control – Theoretical Background Non-Structural Cracks: 18

19. Crack Control – Theoretical Background Appearance (smooth surface > 0.2 mm = public concern) Leakage ( Liquid-retaining structures) Corrosion (cracks can speed up occurrence of corrosion) Reasons for crack width control? 19

20. Crack Control – Theoretical Background Concrete Grade Concrete Cover Steel Stress Bar Diameter Bar Spacing Factors affecting Crack width Code limits the steel stress and max. bar spacing in accordance to the allowable crack width Before Cracking After Cracking 20

21. Crack Control – Theoretical Background Crack Control without crack width calculation 21

22. Crack Control – Theoretical Background 22

23. Crack Control – Theoretical Background Temperature / Shrinkage (restraint) crack development Base restrain free shrinkage of wall 23

24. Crack Control – Theoretical Background Temperature / Shrinkage (restraint) crack development 24

25. Crack Control – Theoretical Background 25

26. Crack Control – Theoretical Background 0.3 percent minimum reinforcement has been found to be acceptable provided that movement joints are less than 30 ft (10 m) apart for concretes made with ASTM C 150 and ASTM C 595 cements. With shrinkage-compensating concrete , joint spacing up to 75 ft (25 m) have been used successfully with 0.3 percent reinforcement (ACI 350R). Minimum temperature and shrinkage reinforcement should be No. 4 (13 mm) bars, spaced not farther than 12 in. (300 mm) on center , each face. Fig. 9.1 shows the ACI 350R recommendations for concretes made with ASTM C 150 and ASTM C 595 cements. 26

27. Crack Control – Theoretical Background 27

28. Water Stop –Installation 28

29. Water Stop –Installation 29

30. Crack Control – Theoretical Background On liquid retaining faces, the tensile stresses due to the combination of direct horizontal tension and bending action shall satisfy the following condition: Additional Requirements –(special codes) 30

31. Rectangular Elevated Tanks 31

32. Rectangular Elevated Tanks 32

33. Rectangular Elevated Tanks 33

34. Rectangular Elevated Tanks 34

35. Rectangular Elevated Tanks 35

36. Rectangular Elevated Tanks 36

37. Rectangular Elevated Tanks 37

38. Rectangular Elevated Tanks 38

39. Rectangular Elevated Tanks 39

40. Rectangular Elevated Tanks 40

41. 41

42. Design as a deep beam Rectangular Elevated Tanks 42

43. Rectangular Elevated Tanks Which is less 43

44. Rectangular Elevated Tanks 44

45. Rectangular Elevated Tanks BMD NFD 45

46. Rectangular Elevated Tanks 46

47. Rectangular Elevated Tanks 47

48. Rectangular Elevated Tanks 48

49. Rectangular Elevated Tanks 49

50. Rectangular Rested & Underground Tanks Earth Pressure considered 50

51. Rectangular Rested & Underground Tanks 51

52. Rectangular Rested & Underground Tanks In case of GWT > base level 52

53. Rectangular Rested & Underground Tanks 53

54. Rectangular Rested & Underground Tanks Cases of loading 54

55. Rectangular Rested & Underground Tanks 55

56. Rectangular Rested & Underground Tanks 56

57. Rectangular Rested & Underground Tanks 57

58. Cylindrical Tanks 58

59. Cylindrical Tanks For small capacities rectangular tanks are generally used and for bigger capacities circular tanks are used. The walls of circular tanks may have flexible joints or rigid joints at the base. Cylindrical Tanks with Flexible Joint at the Base. In these tanks walls are subjected to hydrostatic pressure. The tank wall is designed as thin cylinder. At the base, maximum pressure = wH. As = T / fs “axial tension reinforcement” fs : allowable steel stress considering crack control T 59

60. Cylindrical Tanks 60

61. Cylindrical Tanks 61

62. Cylindrical Tanks Approximate design values Max. Ring Tension: T = (0.8 -0.9) * g w *H *R Max. Wall Thickness: t = T / f ct f ct : Allowable concrete tensile stress Max. Base BM: M b = g w *H *R*t / 4 Max. +ve BM: M +ve = M b /5 62

63. Cylindrical Tanks Example: D = 8 m; H = 12m Assume: fs = 200 MPa; fct = 1.8 MPa Approximate design values Max. Ring Tension: T = (0.9) * 10 *12 *4 = 432 kN Reinforcement: As = 432 *1000 / 200 = Max. Wall Thickness: t = T / f ct f ct : Allowable concrete tensile stress Max. Base BM: M b = g w *H *R*t / 4 Max. +ve BM: M +ve = M b /5 63

64. Cylindrical Tanks The BM for circular slabs are acting in two orthogonal directions 1) the radial direction; 2) the tangential direction The RFT should be placed to cover 1) BM in tang. Dir. 2) BM + axial Tension in radial direction (base shear of wall) 64

65. Cylindrical Tanks 65

66. Cylindrical Tanks 66

67. Cylindrical Tanks The wall is acting as a circular deep beam Wall N.F in vertical direction 67

68. Cylindrical Tanks 68

69. Cylindrical Tanks 69

70. Cylindrical Tanks 70

71. Surfaces of Revolution Surfaces of revolution are membrane structures The thickness is so small  only meridian and ring forces in the plane of the surface can be resisted B.M. only due to fixation at support 71

72. Surfaces of Revolution R: radius normal to axis of revolution of any circular ring at any plane R1: radius of curvature of meridian R2: cross radius curvature along the normal – to axis of rotation W f : Sum of vertical forces above the considered plane Spherical Shell Conical Shell 72

73. Surfaces of Revolution 73

74. Surfaces of Revolution 74

75. Surfaces of Revolution 75

76. Surfaces of Revolution 76

77. Surfaces of Revolution 77

78. Surfaces of Revolution Calculation of Meridian and Ring Forces 78

79. Surfaces of Revolution 79

80. Surfaces of Revolution 80

81. Surfaces of Revolution Example (1) 81

82. Surfaces of Revolution Example (2) 82

83. Surfaces of Revolution Example (2) 83

84. Surfaces of Revolution Design of sections 84

85. Surfaces of Revolution 85

86. Surfaces of Revolution 86

87. Surfaces of Revolution T1 is transmitted to the outer ring beam 87

88. Surfaces of Revolution 88

89. Surfaces of Revolution 89

90. Stability of Elevated Water tanks When a tank containing liquid vibrates, the liquid exerts impulsive and convective hydrodynamic pressure on the tank wall and the tank base in addition to the hydrostatic pressure. In order to include the effect of hydrodynamic pressure in the analysis, tank can be idealized by an equivalent spring mass model, which includes the effect of tank wall – liquid interaction. V H W M (over turning) = V * H B M (balancing) = W * B/2 F.O.S = M (bal.) / M (ot.) 90

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