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Evaluation of MC90 application rules against Bond Test Database
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Transcript of Evaluation of MC90 application rules against Bond Test Database
1/22University of StuttgartInstitute of Construction Materials (IWB)
Evaluation of MC90 application rulesagainst Bond Test Database
fib Task Group 4.5 „Bond Models“– 8th Meeting, November 4, 2005, Stuttgart, Germany –
2/22University of StuttgartInstitute of Construction Materials (IWB)
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)
EVALUATION CRITERIA
3/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 APPLICATION RULES
Design lap length of bars in tension:
s,cal0 s 1 3 4 5 6 b 0,min
s,ef
Al l l l
A
with: s ydb
bd
d fl
4 f
bd 1 2 3 ctdf f
ctk,minctd
c
ff
and
(bond length)
(bond strength)
(concrete tensile strength)
4/22University of StuttgartInstitute of Construction Materials (IWB)
For mean values:
MC90 APPLICATION RULES
yd smf ; ctk,min ctmf f ; c 1.0
and
s sms 1 3 4 5 6
1 2 3 ctm
d 1.0l
4 f
The lap lenght ls can be written to:
s,cal
s,ef
A1.0
A
5/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 APPLICATION RULES
ssm ctm 1 2 3
s 1 3 4 5 6
l 1 1 1 1 14 fd
1 1.0 ;
4 1.0 ;
5 1.0 ;
6 2.0;
1 2.25 ;
2 1.0
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)
6/22University of StuttgartInstitute of Construction Materials (IWB)
ssm ctm 3
s 3
l 19 fd
The mean steel stress for use with the test database:
MC90 APPLICATION RULES
with: ls = lap lenght
ds = bar diameter
fctm = mean concrete tensile strength
3 = concrete confinement factor
3 = bar diameter factor
7/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 COEFFICIENTS
0 20 40 60 80 100 120Concrete Compressive Strength fcm [N/mm2]
Influ
ence
dis
trib
utio
n / T
ende
ncy
MC90
JC & Stuttgart
23
ckctm
ff 1.4
10
14
ckctm
ff 2.310
MC 90:
JC & Stuttgart:
Influence of concrete compressive strength
8/22University of StuttgartInstitute of Construction Materials (IWB)
0 10 20 30 40 50 60Relative Lap Length ls/ds [-]
Influ
ence
dis
trib
utio
n / T
ende
ncy MC90
Stuttgart
MC90 COEFFICIENTS
1
s
s
ld
23
s
s
ld
MC 90:
Stuttgart:
Influence of relative lap length
9/22University of StuttgartInstitute of Construction Materials (IWB)
0,00
0,25
0,50
0,75
1,00
1,25
1,50
1,75
2,00
2,25
2,50
0,00 0,02 0,04 0,06 0,08 0,10 0,12Type of reinforcement (virtual fR [-])
Coe
ffic
ient
1
[-]
plain
intended
ribbed
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
10/22University of StuttgartInstitute of Construction Materials (IWB)
0,00
0,25
0,50
0,75
1,00
1,25
Bond Condition
Coe
ffic
ient
2
[-]
moderate bond
good bond
worse better
MC90 COEFFICIENT 2
MC 90: 2 = 0.7 for moderate bond
2 = 1.0 for good bond
Influence of bond conditions
11/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 COEFFICIENT 3
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
0 10 20 30 40 50 60Bar diameter ds [mm]
Coe
ffic
ient
3
[-]
MC 90
Stuttgart
JC
MC 90:
Stuttgart:
JC:
s
3 ss
1.0 for d 32mm132 d for d 32mm
100
s3
50 d1100
0.2
3s
20 1.2d
Influence of bar diameter
12/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 COEFFICIENT 1
0,00
0,25
0,50
0,75
1,00
1,25
1,50
1,75
Form of bars
Coe
ffic
ient
1/
1 [-
]bent
straight
bent straight
MC 90: ! = 0.7 for bent bars
1 = 1.0 for straight bars
Influence of form of reinforcing bars
13/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 COEFFICIENT 3
0,0
0,5
1,0
1,5
2,0
2,5
3,0
0 10 20 30 40 50 60Confining cover cd [mm]
Coe
ffic
ient
1/
3 [-
]
MC 90
Stuttgartd3
s
c1 0.15 1d
12
d3
s
c1d
MC 90:
Stuttgart:
d 1c min a 2, c , c acc. to MC90
Influence of confinement by concrete
14/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 COEFFICIENT 4
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
0 100 200 300 400 500 600Reinforcement area Ast [mm2]
Coe
ffic
ient
1/
4 [-
]K=0.10
K=0.05
K=0
MC 90:
St St,min4
S
A A1 K
A
K values acc. to MC90
Influence of confinement by transverse reinforcement
15/22University of StuttgartInstitute of Construction Materials (IWB)
MC90 COEFFICIENT 5
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
0,0 1,5 3,0 4,5 6,0 7,5 9,0Transverse pressure [N/mm2]
Coe
ffic
ient
1/
5 [-
]MC 90
MC 90:
5 1 0.04 p
Influence of confinement by transverse pressure
16/22University of StuttgartInstitute of Construction Materials (IWB)
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
0,00
0,25
0,50
0,75
1,00
0 20 40 60 80 100Percentage of lapped bars [%]
Coe
ffic
ient
1/
6 [-
]<20%
25%
33%
50%
>50%
Influence of percentage of the reinforcement lapped
17/22University of StuttgartInstitute of Construction Materials (IWB)
s
3 ss
1.0 for d 32mm132 d
for d 32mm100
EVALUATION OF MC90 APPLICATION RULES
2
3s ck d
sm 3ss
l f c9 1.4 1 1 0.15 1dd 10
0
200
400
600
800
1000
0 200 400 600 800 1000Predicted Steel Stress s [N/mm2]
Mea
sure
d St
eel S
tres
s s [
N/m
m2 ]
Test Database
Linear (Test Database)
Number of tests 363 Average 1,35 Maximum 3,02 Minimum e 0,31 Stand.Deviation 0,52 CoV 0,38 0.05 Fractile 0,50 0.95-Fractile 2,20
18/22University of StuttgartInstitute of Construction Materials (IWB)
14
s ck sd ssm
s ss
l f 50 dc 7 d9 2.3 1 1 0.15 1 1 1 0.3d ld 10 100
REVISED VERSION OF JC
0
200
400
600
800
1000
0 200 400 600 800 1000Predicted Steel Stress s [N/mm2]
Mea
sure
d St
eel S
tres
s s [
N/m
m2 ]
Database
Linear (Database)
Number of tests 336 Average 0,75 Maximum 1,28 Minimum e 0,41 Stand.Deviation 0,13 CoV 0,18 0.05 Fractile 0,53 0.95-Fractile 0,97
19/22University of StuttgartInstitute of Construction Materials (IWB)
12 13 4 2s ck sd
smss
l f 50 dc9 2.3 1 1dd 10 100
REVISED VERSION COMB. OF JC & STUTTGART
0
200
400
600
800
1000
0 200 400 600 800 1000Predicted Steel Stress s [N/mm2]
Mea
sure
d St
eel S
tres
s s [
N/m
m2 ]
Test database
Linear (Test database)
Number of tests 336 Average 1,24 Maximum 2,77 Minimum e 0,73 Stand.Deviation 0,26 CoV 0,21 0.05 Fractile 0,81 0.95-Fractile 1,66
20/22University of StuttgartInstitute of Construction Materials (IWB)
REVISED VERSION OF STUTTGART
0
200
400
600
800
1000
0 200 400 600 800 1000Predicted Steel Stress s [N/mm2]
Mea
sure
d St
eel S
tres
s
s [N
/mm
2 ]
Test database
Linear (Test database)
Number of tests 336 Average 1,52 Maximum 3,08 Minimum e 0,83 Stand.Deviation 0,30 CoV 0,20 0.05 Fractile 1,02 0.95-Fractile 2,01
12 1 0.23 4 2s ck d
smss s
l f 20c9 2.3 1dd 10 d
21/22University of StuttgartInstitute of Construction Materials (IWB)
0
200
400
600
800
1000
0 200 400 600 800 1000Predicted Steel Stress s [N/mm2]
Mea
sure
d St
eel S
tres
s s [
N/m
m2 ]
Test database
Linear (Test database)
Number of tests 336 Average 1,01 Maximum 2,05 Minimum e 0,55 Stand.Deviation 0,20 CoV 0,20 0.05 Fractile 0,68 0.95-Fractile 1,34
12 1 0.23 4 2s ck d
smss s
l f 20c13.5 2.3 1dd 10 d
FINAL REVISED VERSION OF STUTTGART
22/22University of StuttgartInstitute of Construction Materials (IWB)
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“)