University of Stuttgart Institute of Construction Materials (IWB) 1/22 Evaluation of MC90 application rules against Bond Test Database fib Task Group 4.5 „Bond Models“ – 8 th Meeting, November 4, 2005, Stuttgart, Germany –

University of Stuttgart Institute of Construction Materials (IWB) 2/22 General Critera for evaluation of test database: ▫ Good bond conditions („bottom cast bars“) ▫ No confinement by reinforcement (A sw =0) ▫ No confinement by transverse pressure (p=0) ▫ Concrete cover > c nom (c nom =c min +tol.=15mm) ▫ Concrete failure presumed ▫ Minimum concrete strenght (f cm ≥15 N/mm 2 ) ▫ Straight and ribbed bars in tension ▫ All bars lapped (100 % Splice) EVALUATION CRITERIA

University of Stuttgart Institute of Construction Materials (IWB) 3/22 MC90 APPLICATION RULES Design lap length of bars in tension: with: and (bond length) (bond strength) (concrete tensile strength)

University of Stuttgart Institute of Construction Materials (IWB) 4/22 For mean values: MC90 APPLICATION RULES and The lap lenght l s can be written to:

University of Stuttgart Institute of Construction Materials (IWB) 5/22 MC90 APPLICATION RULES The mean steel stress in general: and 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) (ribbed bars) (good bond conditions)

University of Stuttgart Institute of Construction Materials (IWB) 6/22 The mean steel stress for use with the test database: MC90 APPLICATION RULES with: l s = lap lenght d s = bar diameter f ctm = mean concrete tensile strength  3 = concrete confinement factor  3 = bar diameter factor

University of Stuttgart Institute of Construction Materials (IWB) 7/22 MC90 COEFFICIENTS MC 90: JC & Stuttgart: Influence of concrete compressive strength

University of Stuttgart Institute of Construction Materials (IWB) 8/22 MC90 COEFFICIENTS MC 90: Stuttgart: Influence of relative lap length

University of Stuttgart Institute of Construction Materials (IWB) 9/22 MC90 COEFFICIENT  1 MC 90:  1 = 1.0 for plain bars  1 = 1.4 for indented bars  1 = 1.0 for ribbed bars Influence of type of reinforcement

University of Stuttgart Institute of Construction Materials (IWB) 10/22 MC90 COEFFICIENT  2 MC 90:  2 = 0.7 for moderate bond  2 = 1.0 for good bond Influence of bond conditions

University of Stuttgart Institute of Construction Materials (IWB) 11/22 MC90 COEFFICIENT  3 MC 90: Stuttgart: JC: Influence of bar diameter

University of Stuttgart Institute of Construction Materials (IWB) 12/22 MC90 COEFFICIENT  1 MC 90:  ! = 0.7 for bent bars  1 = 1.0 for straight bars Influence of form of reinforcing bars

University of Stuttgart Institute of Construction Materials (IWB) 13/22 MC90 COEFFICIENT  3 MC 90: Stuttgart: Influence of confinement by concrete

University of Stuttgart Institute of Construction Materials (IWB) 14/22 MC90 COEFFICIENT  4 MC 90: Influence of confinement by transverse reinforcement

University of Stuttgart Institute of Construction Materials (IWB) 15/22 MC90 COEFFICIENT  5 MC 90: Influence of confinement by transverse pressure

University of Stuttgart Institute of Construction Materials (IWB) 16/22 MC90 COEFFICIENT  6 MC 90:  6 = 1.2 for ≤ 20 %  6 = 1.4 for 25 %  6 = 1.6 for 33 %  6 = 1.8 for 50 %  6 = 2.0 for > 50% of lapped bars relative to total cross-section Influence of percentage of the reinforcement lapped

University of Stuttgart Institute of Construction Materials (IWB) 17/22 EVALUATION OF MC90 APPLICATION RULES

University of Stuttgart Institute of Construction Materials (IWB) 18/22 REVISED VERSION OF JC

University of Stuttgart Institute of Construction Materials (IWB) 19/22 REVISED VERSION COMB. OF JC & STUTTGART

University of Stuttgart Institute of Construction Materials (IWB) 20/22 REVISED VERSION OF STUTTGART

University of Stuttgart Institute of Construction Materials (IWB) 21/22 FINAL REVISED VERSION OF STUTTGART

University of Stuttgart Institute of Construction Materials (IWB) 22/22 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“)