Bond strength  anddevelopmentlength
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Bond strength  anddevelopmentlength Bond strength anddevelopmentlength Document Transcript

  • FUNDAMENTALS OF FLEXURAL BOND 1
  • BOND STRENGTH AND DEVELOPMENT LENGTH Bond Strength Development LengthFactors Influencing Development Length 2
  • 5.3 ACI CODE PROVISIONS FOR DEVELOPMENT OF TENSION REINFORCEMENTBasic EqnSee book for terms.Simplified Equations for Development LengthAppendix A.10 3 View slide
  • Example 5.1 4 View slide
  • 5
  • 6
  • 5.4 ANCHORAGE OF TENSION BARS BY HOOKSStandard DimensionsFig 5.9: Standard bar Hooks: (a) Main reinforcement (b) stirrups and ties 7
  •  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
  • 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
  • Example 5.2 10
  • 5.5 ANCHORAGE REQUIREMENTS FOR WEB REINFORCEMENT Fig 5.12 11
  • 5.7 DEVELOPMENT BARS IN COMPRESSION  Development length should not be less than 8 in.Appendix Table A11 12
  • 5.8 BUNDLED BARS 13
  • 5.9 BAR CUTOFF AND BEND POINTS IN BEAMSTheoretical Points of Cutoff or Bend Fig.5.13 Bar cutoff points from moment diagrams 14
  • 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
  • Fig 5.15: Cutoff or bend points for bars in approximately equal spans with uniformly distributed loads 16
  • 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
  • COLUMN 18
  • Example 19