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Evaluation of MC90 application rules against Bond Test Database

fib Task Group 4.5 „Bond Models“ – 8 th Meeting, November 4, 2005, Stuttgart, Germany –. Evaluation of MC90 application rules against Bond Test Database. EVALUATION CRITERIA. General Critera for evaluation of test database: Good bond conditions („bottom cast bars“)

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Evaluation of MC90 application rules against Bond Test Database

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  1. fib Task Group 4.5 „Bond Models“ – 8th Meeting, November 4, 2005, Stuttgart, Germany – Evaluation of MC90 application rulesagainst Bond Test Database

  2. EVALUATION CRITERIA General Critera for evaluation of test database: • Good bond conditions („bottom cast bars“) • No confinement by reinforcement (Asw=0) • No confinement by transverse pressure (p=0) • Concrete cover > cnom (cnom=cmin+tol.=15mm) • Concrete failure presumed • Minimum concrete strenght (fcm≥15 N/mm2) • Straight and ribbed bars in tension • All bars lapped (100 % Splice)

  3. MC90 APPLICATION RULES Design lap length of bars in tension: with: (bond length) (bond strength) and (concrete tensile strength)

  4. MC90 APPLICATION RULES For mean values: and The lap lenght ls can be written to:

  5. MC90 APPLICATION RULES The mean steel stress in general: For use with the test database the factors are: (straight bars) (no confinement by reinforcement) (no confinement by transverse pressure) (only used for MC90 / 100 % of bars lapped) and (ribbed bars) (good bond conditions)

  6. MC90 APPLICATION RULES The mean steel stress for use with the test database: with: ls = lap lenght ds = bar diameter fctm = mean concrete tensile strength a3 = concrete confinement factor h3 = bar diameter factor

  7. MC90 COEFFICIENTS Influence of concrete compressive strength MC 90: JC & Stuttgart:

  8. MC90 COEFFICIENTS Influence of relative lap length MC 90: Stuttgart:

  9. MC90 COEFFICIENT h1 Influence of type of reinforcement MC 90: h1 = 1.0 for plain bars h1 = 1.4 for indented bars h1 = 1.0 for ribbed bars

  10. MC90 COEFFICIENT h2 Influence of bond conditions MC 90: h2 = 0.7 for moderate bond h2 = 1.0 for good bond

  11. MC90 COEFFICIENT h3 Influence of bar diameter MC 90: JC: Stuttgart:

  12. MC90 COEFFICIENT a1 Influence of form of reinforcing bars MC 90: a! = 0.7 for bent bars a1 = 1.0 for straight bars

  13. MC90 COEFFICIENT a3 Influence of confinement by concrete MC 90: Stuttgart:

  14. MC90 COEFFICIENT a4 Influence of confinement by transverse reinforcement MC 90:

  15. MC90 COEFFICIENT a5 Influence of confinement by transverse pressure MC 90:

  16. MC90 COEFFICIENT a6 Influence of percentage of the reinforcement lapped MC 90: a6 = 1.2 for ≤ 20 % a6 = 1.4 for 25 % a6 = 1.6 for 33 % a6 = 1.8 for 50 % a6 = 2.0 for > 50% of lapped bars relative to total cross-section

  17. EVALUATION OF MC90 APPLICATION RULES

  18. REVISED VERSION OF JC

  19. REVISED VERSION COMB. OF JC & STUTTGART

  20. REVISED VERSION OF STUTTGART

  21. FINAL REVISED VERSION OF STUTTGART

  22. FUTURE WORK Further investigations needed to clarify the influence and the treatment of: • Confinement by transverse reinforcement • Confinement by transverse pressure • Anchorages/Laps with (ribbed) headed bars • Lapping all bars in a section • Anchorages/Laps under moderate bond cond.(„top cast effect“)

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