This document discusses fundamentals of flexural bond including: 1. Bond strength and development length requirements for tension reinforcement according to the ACI code. 2. Simplified equations and factors that influence development length calculations. 3. Anchorage requirements including standard dimensions for bar hooks, development lengths for hooked bars, and transverse reinforcement requirements. 4. Additional topics on anchorage of web reinforcement, development bars in compression, bundled bars, bar cutoffs in beams, and bar splices. Diagrams and examples are provided to illustrate key concepts.

1. FUNDAMENTALS OF FLEXURAL BOND
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2. BOND STRENGTH AND DEVELOPMENT LENGTH
Bond Strength
Development Length
Factors Influencing Development Length
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3. 5.3 ACI CODE PROVISIONS FOR DEVELOPMENT
OF TENSION REINFORCEMENT
Basic Eqn
See book for terms.
Simplified Equations for Development Length
Appendix A.10
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4. Example 5.1
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5. 5

6. 6

7. 5.4 ANCHORAGE OF TENSION BARS BY HOOKS
Standard Dimensions
Fig 5.9: Standard bar Hooks: (a) Main reinforcement (b) stirrups and ties
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8.  For stirrup and tie hooks, for sizes No. 5 and smaller, the inside diameter of
bend should not be less than 4 bar diameters, according to ACI Code
 For stirrups and tie hooks, greater than No. 5, Table 5.2 applies.
Development Length and Modification Factors for Hooked Bars
Fig5.10: Bar details for development of standard hooks
For standard hooks, the development length is
 ldh should not be less than 8 bar diameter or 6 in.
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9. Fig. 5.11: Transverse reinforcement requirements at discontinuous ends of
members with small cover distances (less than 2.5in.)
 0.8 does not apply
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10. Example 5.2
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11. 5.5 ANCHORAGE REQUIREMENTS FOR WEB
REINFORCEMENT
Fig 5.12
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12. 5.7 DEVELOPMENT BARS IN COMPRESSION
 Development length should not be less than 8 in.
Appendix Table A11
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13. 5.8 BUNDLED BARS
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14. 5.9 BAR CUTOFF AND BEND POINTS IN BEAMS
Theoretical Points of Cutoff or Bend
Fig.5.13 Bar cutoff points from moment diagrams
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15. Practical Considerations and ACI Code requirements
Tensile steel should not be discontinued exactly at the Theoretical Cutoff point
 Redistribution of forces occur
Moment diagram different due to
 approximation of real load,
 approximation in analysis,
 superimposed effect of settlement or lateral loads
Fig 5.14: Bar cutoff requirements of the ACI Code
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16. Fig 5.15: Cutoff or bend points for bars in approximately equal spans with
uniformly distributed loads
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17. Bar Splices
Splices for No. 11 and smaller are usually made simply by lapping the bars a
sufficient distance to transfer stress by bond from one bar to the other. Lapped
bars are usually placed in contact and lightly wired.
Splices may also be by welding, sleeves or mechanical devices.
TENSION
COMPRESSION
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18. COLUMN
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19. Example
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