Development length

Lapping
Cutoff
OMRF, IMRF, SMRF
Stirrup spacing

1. Development Length Toe Myint Naing Curtin Sarawak Intern KSI Engineering

2. Bond Basic assumptions in Flexural theory Strain in concrete is the same as in reinforcing bars at the same level, provided that the bond between the steel and concrete is sufficient to keep them acting together under the different load stages i.e., no slip can occur between the two materials. No bond, no development length, no anchorage, rebar will pull loose from concrete 2 Help in transferring force from steel to concrete and concrete to steel.

3. The stress which is acting on the outer interface of steel to the surrounding concrete is called bond stress. Bond stresses are also drastically affected by the development of tension cracks in the concrete. At a point where a crack occurs, all of the longitudinal tension will be resisted by the reinforcing bar. At a small distance along the bar at a point away from the crack, the longitudinal tension will be resisted by both the bar and the uncracked concrete. 3 Bond Stress

4. Development Length is the length of embedment necessary to develop the full tensile strength of the bar, controlled by either pullout or splitting 4

5. 5 Development Length Development lengths are needed in: Lapping Hooks Cut off

6. 6 Development Length in tension Tension Development Length Ldt   (1) ( )=reinforcement location factor =1.3 for top horizontal reinforcement bars (i.e., 12” or more of concrete is cast in a single concreting below the development length of splice in question) =1.0 for other reinforcement bars  

7. 7 Development Length Tension Development Length Ldt   (2) =Coating factor =1.5 for epoxy-coated bar with cover < 3 or clear spacing < 6 =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (1) ( )=reinforcement location factor =1.3 for top horizontal reinforcement bars (i.e., 12” or more of concrete is cast in a single concreting below the development length of splice in question) =1.0 for other reinforcement bars   Development Length in tension

8. 8 Development Length Tension Development Length Ldt   (2) =Coating factor =1.5 for epoxy-coated bar with cover < 3 or clear spacing < 6 =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (1) ( )=reinforcement location factor =1.3 for top horizontal reinforcement bars (i.e., 12” or more of concrete is cast in a single concreting below the development length of splice in question) =1.0 for other reinforcement bars   (3) =reinforcement size factor =0.8 for No.6 and smaller bars =1.0 for No.7 and larger bars   Development Length in tension

9. 9 Development Length Tension Development Length Ldt   (2) =Coating factor =1.5 for epoxy-coated bar with cover < 3 or clear spacing < 6 =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (1) ( )=reinforcement location factor =1.3 for top horizontal reinforcement bars (i.e., 12” or more of concrete is cast in a single concreting below the development length of splice in question) =1.0 for other reinforcement bars   (3) =reinforcement size factor =0.8 for No.6 and smaller bars =1.0 for No.7 and larger bars   (4) =lightweight aggregate concrete factor =1.3 for all-lightweight and sand-lightweight concrete =1.0 for normal weight concrete   Development Length in tension

10. 10 Development Length Tension Development Length Ldt   (2) =Coating factor =1.5 for epoxy-coated bar with cover < 3 or clear spacing < 6 =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (1) ( )=reinforcement location factor =1.3 for top horizontal reinforcement bars (i.e., 12” or more of concrete is cast in a single concreting below the development length of splice in question) =1.0 for other reinforcement bars   (3) =reinforcement size factor =0.8 for No.6 and smaller bars =1.0 for No.7 and larger bars   (4) =lightweight aggregate concrete factor =1.3 for all-lightweight and sand-lightweight concrete =1.0 for normal weight concrete   (3) =spacing or cover dimension 2.5   Development Length in tension

11. 11 Development Length Tension Development Length Ldt   (2) =Coating factor =1.5 for epoxy-coated bar with cover < 3 or clear spacing < 6 =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (1) ( )=reinforcement location factor =1.3 for top horizontal reinforcement bars (i.e., 12” or more of concrete is cast in a single concreting below the development length of splice in question) =1.0 for other reinforcement bars   (3) =reinforcement size factor =0.8 for No.6 and smaller bars =1.0 for No.7 and larger bars   (4) =lightweight aggregate concrete factor =1.3 for all-lightweight and sand-lightweight concrete =1.0 for normal weight concrete   (3) =spacing or cover dimension 2.5   (3) 100psi   Development Length in tension

12. 12 Development Length Tension Development Length Ldt       For No.6 (20mm) and smaller bars, For No.7 (22mm) and larger bars,     For Normal concrete, Simplified Tension Development Length     Development Length in tension

13. 13 Development Length Ldt For No.6 (20mm) and smaller bars,     Simplified Tension Development Length Modification factor may also be modified by ( ) 12” (in all cases)   For No.7 (22mm) and larger bars, Development Length in tension

14. 14 Development Length Ldt Simplified Tension Development Length by table Modification factor may also be modified by ( ) 12” (in all cases)   Development Length in tension

15. 15 Standard Bar Hooks When desired tensile stress in a bar cannot be developed by bond alone, it is necessary to provide special anchorage at the end of the bar Bar Size, db Minimum Diameter, Ø No.3 (10mm) through No.8 (25mm) 6 No.9,10 and 11 (No.29,32 and 36 ) 8 No.14 (43mm) through No.18 (57mm) 10 Bar Size, db Minimum Diameter, Ø No.3 (10mm) through No.8 (25mm) No.9,10 and 11 (No.29,32 and 36 ) No.14 (43mm) through No.18 (57mm) Hooked-Bar details for Development of standard hook (b) Stirrups and Ties (a) Main Reinforcement 22

16. 16 Development Length of Hooked deformed Bar in tension,     (1) =Coating factor =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement  

17. 17   (1) =Coating factor =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (2) =lightweight aggregate concrete factor =1.3 for all-lightweight and sand-lightweight concrete =1.0 for normal weight concrete   Development Length of Hooked deformed Bar in tension,  

18. 18 Development Length of Hooked deformed Bar,     (1) =Coating factor =1.2 for all other epoxy-coated bar =1.0 for Uncoated and zinc-coated reinforcement   (2) =lightweight aggregate concrete factor =1.3 for all-lightweight and sand-lightweight concrete =1.0 for normal weight concrete   For Normal Concrete,   Modification factors may be modified by ( ) For No.11 and smaller bar hooks with side cover 2.5” and for 90 hooks with clear cover on bar extension 2.0”, is multiplied by 0.7 For No.11 and smaller bars hooks that are enclosed within ties or stirrups at spacing along , is multiplied by 0.8   Development Length of Hooked deformed Bar in tension,  

19. Development Length of Hooked deformed Bar in tension,   19 X 0.7 X 0.8 X 0.8

20. 20 Development Length or Anchorage ( or )   (a) (b) (c) Hook development length, is used only when development length, is not adequate  

21. 21 Development Length Compression Development Length Ldc   shorter than   Modification factor may be modified by ( ) For No.4 ties < 4” c/c spacing , may also be modified by 0.75 8” (in all cases)   Hooks shall not be used to develop bars in compression (12.5.5 ACI 318-05) Development Length in compression

22. End Anchorage Lengths 22 (A) Using Standard Hooks         Wide Column Clear cover   Clear cover   Primary Beam (a) Beam – Column Connections (b) Beam – Girder Connections To pg-15

23. End Anchorage Lengths 23 (B) Using Alternate Method     Narrow Column Clear cover   Clear cover   Primary Beam (a) Beam – Column Connections (b) Beam – Girder Connections        

24. End Anchorage Lengths 24 Anchorage Length for Girder with smaller bar sizes - 2.5 (for the outermost layer) - 6.5 (for the second layer) - 10.5 (for the third layer) h, b = depth and width of primary beam   h

25. End Anchorage Lengths 25 Structural Integrity Requirement

26. Development Length from column to footing For the case where all the column bars are in compression, the dowels must extend into the footing a compression development length  l dc  . (a)Longitudinal bars in column are in compression The dowel bars are usually hooked and extend to the level of the flexural reinforcement in the footing. According to Section 12.5.5 ACI 318-05, the hooked portion of the dowels cannot be considered effective for developing the dowel bars in compression .  26

27. Development Length from column to footing Either direct or uplift forces or transfer by a moment tensile force can act from column, the dowels must extend into the footing a tension development length  l dt  . (b)Longitudinal bars in column are in tension Tensile anchorage of the dowel bars into a footing is typically accomplished by providing 90-degree standard hooks at the ends of the dowel bars with the development length of the hooked bar, ldh , determined in accordance with Section 12.5 of ACI 318-14. 27

28. Development Length Toe Myint Naing Curtin Sarawak Intern KSI Engineering

29. Development Length (Lap splice in Tension) 29 Class A Splice: ……………………….……….……….…..1.0 12” Class B Splice: ………………………….….………….…..1.3 12”   For No.6 (20mm) and smaller bars,     For No.7 (22mm) and larger bars, Lap splicing of No.14 and No.18 bars in tension is prohibited. 50%

30. Development Length (Lap splice in Compression) 30 60,000 psi 60,000 psi 0.0005 (0.0009 -24) 12” For < 3000 psi, shell be increased by one-third   Where ties throughout the lap splice length have an effective area 0.0015h s, lap splice length shall be permitted to be multiplied by 0.83 12”   Lap splicing of No.14 and No.18 bars to No.11 and smaller bars in compression shell be permitted when = larger of [ of larger bar and of smaller bar ]  

31. Development Length (Lap splice in Column) 31 Column – no restrictions Column – no restrictions Column – mid

32. Development Length (Lap splice in Column) 32 50% LAPPING, CQHP

33. Development Length (Lap splice in Tension only in Column) 33 Class A Splice: ……………………….……….……….…..1.0 12” Class B Splice: ………………………….….………….…..1.3 12”   For No.6 (20mm) and smaller bars,     For No.7 (22mm) and larger bars, Lap splicing of No.14 and No.18 bars in tension is prohibited. 100%

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59. Development Length (Lap splice in Beam) 59 Ordinary Moment-Resisting Frame Beam Top Bar – Mid Bot Bar – At Support or 2h Beam Top Bar – Mid Bot Bar – Outside 2h within L/3

60. Development Length (Lap splice in Beam) 60 Ordinary Moment-Resisting Frame For closed stirrups for torsion spacing, s max = or 12”  

61. Development Length (Lap splice in Beam) 61 Intermediate Moment-Resisting Frame Special Moment-Resisting Frame Outside 2h ACI 318-05 ACI 318-08 Stirrups without seismic hook Stirrups with seismic hook Beam Top Bar – Mid Bot Bar – Mid

62. Development Length (Lap splice in Beam) 62 Hoop reinforcement for beams Crosstie — A continuous reinforcing bar having a seismic hook at one end and a hook not less than 90° with at least a 6d b extension at the other end . Hoop — A closed tie or continuously wound tie. A closed tie can be made up of several reinforcement elements each having seismic hooks at both ends . A continuously wound tie shall have a seismic hook at both ends.

63. Development Length (OMRF) 63 Slabs (Cutoff)

64. Development Length 64 Bars must extend the longer of d or 12db past the flexural cutoff points except at supports or the ends of cantilevers Structural Integrity Requirement

65. 65 Simple Supports : At least one-third of the positive moment reinforcement must be extended 15 cm. into the supports Structural Integrity Requirement Development Length

66. 66 Continuous interior beams with closed stirrups : At least one-fourth of the positive moment reinforcement must be extended 15 cm. into the support Structural Integrity Requirement Development Length

67. 67 Continuous interior beams without closed stirrups : At least one-fourth of the positive moment reinforcement must be continuous or shall be spliced near the support with a class B tension splice and at non-continuous supports be terminated with a standard hook Splice Class ACI 318-05 ACI 318-08 Class A Class B Structural Integrity Requirement Development Length

68. 68 Beams forming part of a frame that is the primary lateral load resisting system for the building .: This reinforcement must be anchored to develop the specified yield strength, fy , at the face of the support Structural Integrity Requirement Development Length

69. 69 Interior beams : At least one-third of the negative moment reinforcement must be extended by the greatest of d, 12 d b or past the negative moment point of inflection.   Structural Integrity Requirement Development Length

70. 70 Perimeter beams: In addition, of the (-) reinforcement required at the support must be made continuous at mid-span. This can be achieved by means of a class B tension splice at mid-span   Splice Class ACI 318-05 ACI 318-08 Class A Class B Structural Integrity Requirement Development Length

71. Q & A 71