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:
1. Lapping
2. Hooks
3. Cut off

6. 6
Development Length in tension
Tension Development Length Ldt
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
(1) ψ 𝑡(𝛼)=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
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
(2) ψ 𝑒 =Coating factor
=1.5 for epoxy-coated bar with cover < 3𝑑 𝑏 or
clear spacing < 6𝑑 𝑏
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(1) ψ 𝑡(𝛼)=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
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
(2) ψ 𝑒 =Coating factor
=1.5 for epoxy-coated bar with cover < 3𝑑 𝑏 or
clear spacing < 6𝑑 𝑏
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(1) ψ 𝑡(𝛼)=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) ψ 𝑠 =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
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
(2) ψ 𝑒 =Coating factor
=1.5 for epoxy-coated bar with cover < 3𝑑 𝑏 or
clear spacing < 6𝑑 𝑏
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(1) ψ 𝑡(𝛼)=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) ψ 𝑠 =reinforcement size factor
=0.8 for No.6 and smaller bars
=1.0 for No.7 and larger bars
(4) λ =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
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
(2) ψ 𝑒 =Coating factor
=1.5 for epoxy-coated bar with cover < 3𝑑 𝑏 or
clear spacing < 6𝑑 𝑏
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(1) ψ 𝑡(𝛼)=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) ψ 𝑠 =reinforcement size factor
=0.8 for No.6 and smaller bars
=1.0 for No.7 and larger bars
(4) λ =lightweight aggregate concrete factor
=1.3 for all-lightweight and
sand-lightweight concrete
=1.0 for normal weight concrete
(3) 𝑐 𝑏 =spacing or cover dimension
(𝑐 𝑏+𝐾𝑡𝑟)
𝑑 𝑏
≤2.5
Development Length in tension

11. 11
Development Length
Tension Development Length Ldt
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
(2) ψ 𝑒 =Coating factor
=1.5 for epoxy-coated bar with cover < 3𝑑 𝑏 or
clear spacing < 6𝑑 𝑏
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(1) ψ 𝑡(𝛼)=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) ψ 𝑠 =reinforcement size factor
=0.8 for No.6 and smaller bars
=1.0 for No.7 and larger bars
(4) λ =lightweight aggregate concrete factor
=1.3 for all-lightweight and
sand-lightweight concrete
=1.0 for normal weight concrete
(3) 𝑐 𝑏 =spacing or cover dimension
(𝑐 𝑏+𝐾𝑡𝑟)
𝑑 𝑏
≤2.5
(3) 𝑓′ 𝑐 ≤ 100psi
Development Length in tension

12. 12
Development Length
Tension Development Length
Ldt
𝐿 𝑑 =
3
40
×
𝑓𝑦
𝑓′ 𝑐
×
ψ 𝑡ψ 𝑒ψ 𝑠λ
(𝑐 𝑏 + 𝐾𝑡𝑟)
𝑑 𝑏
× 𝑑 𝑏
𝐿 𝑑 =
𝑓𝑦ψ 𝑡ψ 𝑒λ
25 𝑓′ 𝑐
× 𝑑 𝑏
𝐿 𝑑 =
𝑓𝑦ψ 𝑡ψ 𝑒λ
20 𝑓′ 𝑐
× 𝑑 𝑏
For No.6 (20mm) and smaller bars,
For No.7 (22mm) and larger bars,
𝐿 𝑑 =
𝑓𝑦 𝛼
25 𝑓′ 𝑐
× 𝑑 𝑏
𝐿 𝑑 =
𝑓𝑦 𝛼
20 𝑓′ 𝑐
× 𝑑 𝑏
For Normal concrete,Simplified Tension Development Length
𝐿 𝑑:
1
𝑓′ 𝑐
𝐿 𝑑: 𝑑 𝑏
𝐿 𝑑: 𝑓𝑦
Development Length in tension

13. 13
Development Length
Ldt
For No.6 (20mm) and smaller bars, 𝐿 𝑑 =
𝑓𝑦 𝛼
25 𝑓′ 𝑐
× 𝑑 𝑏 ≥ 12"
𝐿 𝑑 =
𝑓𝑦 𝛼
20 𝑓′ 𝑐
× 𝑑 𝑏 ≥ 12"
Simplified Tension Development Length
Modification factor
𝑙 𝑑 may also be modified by (
As required
As provided
)
𝑙 𝑑 ≥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
𝑙 𝑑 may also be modified by (
As required
As provided
)
𝑙 𝑑 ≥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 𝑑 𝑏
No.9,10 and 11 (No.29,32 and 36 ) 8 𝑑 𝑏
No.14 (43mm) through No.18 (57mm) 10 𝑑 𝑏
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, 𝐼 𝑑ℎ
𝐿 𝑑ℎ =
0.02ψ 𝑒λ𝑓𝑦
𝑓′ 𝑐
× 𝑑 𝑏
(1) ψ 𝑒 =Coating factor
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement

17. 17
𝐿 𝑑ℎ =
0.02ψ 𝑒λ𝑓𝑦
𝑓′ 𝑐
× 𝑑 𝑏
(1) ψ 𝑒 =Coating factor
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(2) λ =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, 𝐼 𝑑ℎ

18. 18
Development Length of Hooked deformed Bar, 𝐼 𝑑ℎ
𝐿 𝑑ℎ =
0.02ψ 𝑒λ𝑓𝑦
𝑓′ 𝑐
× 𝑑 𝑏
(1) ψ 𝑒 =Coating factor
=1.2 for all other epoxy-coated bar
=1.0 for Uncoated and zinc-coated reinforcement
(2) λ =lightweight aggregate concrete factor
=1.3 for all-lightweight and
sand-lightweight concrete
=1.0 for normal weight concrete
For Normal Concrete,
𝐿 𝑑ℎ =
0.02𝑓𝑦
𝑓′ 𝑐
× 𝑑 𝑏
Modification factors
𝑙 𝑑ℎ may be modified by (
As required
As provided
)
For No.11 and smaller bar hooks with side cover ≥2.5” and for 90° hooks
with clear cover on bar extension ≥2.0”, 𝑙 𝑑ℎ is multiplied by 0.7
For No.11 and smaller bars hooks that are enclosed within ties or stirrups
at spacing ≤ 3𝑑 𝑏 along 𝑙 𝑑ℎ, 𝑙 𝑑ℎ is multiplied by 0.8
Development Length of Hooked deformed Bar in
tension, 𝐼 𝑑ℎ

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

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

21. 21
Development Length
Compression Development Length Ldc
𝐿 𝑑 =
0.02𝑓𝑦
𝑓′ 𝑐
× 𝑑 𝑏 ≥ 0.0003𝑓𝑦 ≥ 8"
𝐿 𝑑𝑐 shorter than 𝐿 𝑑𝑡
Modification factor
𝑙 𝑑 may be modified by (
As required
As provided
)
For No.4 ties < 4” c/c spacing , 𝑙 𝑑 may also be modified by 0.75
𝑙 𝑑 ≥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
𝑙 𝑏1 ≥ 𝑙 𝑑ℎ ≥ 8𝑑 𝑏 𝑜𝑟 6"
𝑙 𝑎1 ≥ 𝑙 𝑑ℎ ≥ 8𝑑 𝑏 𝑜𝑟 6"
𝑙 𝑏1 ≥ 𝑙 𝑑ℎ ≥ 8𝑑 𝑏 𝑜𝑟 6"
𝑙 𝑎1 ≥ 𝑙 𝑑ℎ ≥ 8𝑑 𝑏 𝑜𝑟 6"
Wide Column
Clear cover
≥ 2"
Clear cover
≥ 2"
Primary
Beam
(a) Beam – Column Connections (b) Beam – Girder Connections
To pg-15

23. End Anchorage Lengths
23
(B) Using Alternate Method
𝑙𝑏2≥𝑙𝑑ℎ+14𝑑𝑏
𝑙 𝑎2 ≥ 𝑙 𝑑ℎ + 14𝑑 𝑏
Narrow Column
Clear cover
≥ 2"
Clear cover
≥ 2"
Primary
Beam
(a) Beam – Column Connections (b) Beam – Girder Connections
𝑙 𝑎2 ≥ 𝑙 𝑑ℎ + 14𝑑 𝑏
𝑙𝑏2≥𝑙𝑑ℎ+11𝑑𝑏
≥ 8𝑑 𝑏 𝑜𝑟 6"
≥ 8𝑑 𝑏 𝑜𝑟 6"

24. End Anchorage Lengths
24
Anchorage Length for Girder with smaller bar sizes
𝑙 𝑚𝑎𝑥 ≈ 𝑏 + ℎ − 5.875 - 2.5 𝑑 𝑏 (for the outermost layer)
𝑙 𝑚𝑎𝑥 ≈ 𝑏 + ℎ − 5.875 - 6.5 𝑑 𝑏 (for the second layer)
𝑙 𝑚𝑎𝑥 ≈ 𝑏 + ℎ − 5.875 - 10.5 𝑑 𝑏 (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 ldc .
(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 ldt .
(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 inTension)
29
Class A Splice: 𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑡𝑒𝑛……………………….……….……….…..1.0𝑙 𝑑 ≥ 12”
Class B Splice: 𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑡𝑒𝑛………………………….….………….…..1.3𝑙 𝑑 ≥ 12”
For No.6 (20mm)
and smaller bars,
𝐿 𝑑 =
𝑓𝑦 𝛼
25 𝑓′ 𝑐
× 𝑑 𝑏
𝐿 𝑑 =
𝑓𝑦 𝛼
20 𝑓′ 𝑐
× 𝑑 𝑏
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
𝒇 𝒚 ≤ 60,000 psi 𝒇 𝒚 >60,000 psi
𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑐𝑜𝑚 0.0005𝑓𝑦 𝑑 𝑏 (0.0009𝑓𝑦-24) 𝑑 𝑏 ≥ 12”
For 𝑓′ 𝑐 < 3000 psi, 𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑐𝑜𝑚 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
𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑐𝑜𝑚 = larger of [ 𝑙 𝑑𝑐 of larger bar and 𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑐𝑜𝑚 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 inTension only in Column)
33
Class A Splice: 𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑡𝑒𝑛……………………….……….……….…..1.0𝑙 𝑑 ≥ 12”
Class B Splice: 𝑙 𝑠𝑝𝑙𝑖𝑐𝑒,𝑡𝑒𝑛………………………….….………….…..1.3𝑙 𝑑 ≥ 12”
For No.6 (20mm)
and smaller bars,
𝐿 𝑑 =
𝑓𝑦 𝛼
25 𝑓′ 𝑐
× 𝑑 𝑏
𝐿 𝑑 =
𝑓𝑦 𝛼
20 𝑓′ 𝑐
× 𝑑 𝑏
For No.7 (22mm)
and larger bars,
Lap splicing of No.14 and No.18 bars
in tension is prohibited.
100%

34. Development Length (Lap splice in Column)
34

35. Development Length (Lap splice in Column)
35

36. Development Length (Lap splice in Column)
36

37. Development Length (Lap splice in Column)
37

38. Development Length (Lap splice in Column)
38

39. Development Length (Lap splice in Column)
39

40. Development Length (Lap splice in Column)
40

41. Development Length (Lap splice in Column)
41

42. Development Length (Lap splice in Column)
42

43. Development Length (Lap splice in Column)
43

44. Development Length (Lap splice in Column)
44

45. Development Length (Lap splice in Column)
45

46. Development Length (Lap splice in Column)
46

47. Development Length (Lap splice in Column)
47

48. Development Length (Lap splice in Column)
48

49. Development Length (Lap splice in Column)
49

50. Development Length (Lap splice in Column)
50

51. Development Length (Lap splice in Column)
51

52. Development Length (Lap splice in Column)
52

53. Development Length (Lap splice in Column)
53

54. Development Length (Lap splice in Column)
54

55. Development Length (Lap splice in Column)
55

56. Development Length (Lap splice in Column)
56

57. Development Length (Lap splice in Column)
57

58. Development Length (Lap splice in Column)
58

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, smax =
𝑃ℎ
8
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 6db 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 db or
𝑙 𝑛
16
past the negative moment point of inflection.
Structural Integrity Requirement
Development Length

70. 70
Perimeter beams: In addition,
1
6
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