Bond strength anddevelopmentlength

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Bond strength anddevelopmentlength

  1. 1. FUNDAMENTALS OF FLEXURAL BOND 1
  2. 2. BOND STRENGTH AND DEVELOPMENT LENGTH Bond Strength Development LengthFactors Influencing Development Length 2
  3. 3. 5.3 ACI CODE PROVISIONS FOR DEVELOPMENT OF TENSION REINFORCEMENTBasic EqnSee book for terms.Simplified Equations for Development LengthAppendix A.10 3
  4. 4. Example 5.1 4
  5. 5. 5
  6. 6. 6
  7. 7. 5.4 ANCHORAGE OF TENSION BARS BY HOOKSStandard DimensionsFig 5.9: Standard bar Hooks: (a) Main reinforcement (b) stirrups and ties 7
  8. 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 hooksFor standard hooks, the development length is  ldh should not be less than 8 bar diameter or 6 in. 8
  9. 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 9
  10. 10. Example 5.2 10
  11. 11. 5.5 ANCHORAGE REQUIREMENTS FOR WEB REINFORCEMENT Fig 5.12 11
  12. 12. 5.7 DEVELOPMENT BARS IN COMPRESSION  Development length should not be less than 8 in.Appendix Table A11 12
  13. 13. 5.8 BUNDLED BARS 13
  14. 14. 5.9 BAR CUTOFF AND BEND POINTS IN BEAMSTheoretical Points of Cutoff or Bend Fig.5.13 Bar cutoff points from moment diagrams 14
  15. 15. Practical Considerations and ACI Code requirementsTensile 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 15
  16. 16. Fig 5.15: Cutoff or bend points for bars in approximately equal spans with uniformly distributed loads 16
  17. 17. Bar SplicesSplices for No. 11 and smaller are usually made simply by lapping the bars asufficient distance to transfer stress by bond from one bar to the other. Lappedbars are usually placed in contact and lightly wired.Splices may also be by welding, sleeves or mechanical devices.TENSIONCOMPRESSION 17
  18. 18. COLUMN 18
  19. 19. Example 19

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