AMCM 2011 Presentation for "Numerical analysis of early-age thermal and moisture effects in RC wall"
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Transcript of AMCM 2011 Presentation for "Numerical analysis of early-age thermal and moisture effects in RC wall"
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Numerical analysis of early-age
thermal and moisture e�ects in RC wall
DSc. Eng. Barbara KLEMCZAKMSc. Eng. Agnieszka KNOPPIK�WRÓBEL
Silesian University of TechnologyFaculty of Civil Engineering
Cracow, 14 June 2011
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IntroductionNumerical model
Analysis of RC wallConclusions
Introduction
concrete curing
cement hydration process
dissipation of heat and migration of moisture
temperature and moisture gradients
stresses
self-induced, restraint stresses in structure
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Introduction
thermal�moisture in�uences
massive structures
foundations
gravity dams
medium-thick restrained structures
RC walls of tanks, abutments, castagainst old foundation
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Thermal and moisture analysisThermal�shrinkage strainsStress analysisImplementation
General assumptions
1 phenomenological modeldecoupling of thermal�moisture and mechanical �elds
full coupling of thermal�moisture �elds
2 stress state determined under the assumption thatthermal�moisture strains have distort character
3 viscoelasto�viscoplastic material model of concrete
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Thermal and moisture analysisThermal�shrinkage strainsStress analysisImplementation
Thermal and moisture analysis
Coupled thermal�moisture equations
T = div(αTT gradT + αTW gradc) +1cbρ
qv
c = div(αWW gradc + αWT gradT )− Kqv
Initial conditions
T (xi , t = 0) = Tp(xi , 0)
c(xi , t = 0) = cp(xi , 0)
Boundary conditions
nT (αTT gradT + αTW gradc) + q = 0
nT (αWW gradc + αWT gradT ) + η = 0
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Thermal and moisture analysisThermal�shrinkage strainsStress analysisImplementation
Thermal�shrinkage strains
Imposed thermal�shrinkage strains εn:
volumetric strains
dεn =[dεnx dεny dεnz 0 0 0
]calculated based on predetermined temperature and humidity
dεnx = dεny = dεnz = αT dT + αW dW
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Thermal and moisture analysisThermal�shrinkage strainsStress analysisImplementation
Stress analysis
viscoelastic area
σ = Dve(ε− εn − εc)
viscoelasto�viscoplastic area
σ = Dve (ε− εn − εc − εvp)
Figure 1: Failure surface
possibility of crack occurrence
sl =τoct
τ foct
Figure 2: E�ort level
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Thermal and moisture analysisThermal�shrinkage strainsStress analysisImplementation
Implementation
A set of programs:
TEMWIL
thermal�moisture �elds
MAFEM
stress analysis
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
Input data
concrete class C25/30, steel class RB400cement type CEM I 32.5R, 450 kg/m3,temp.: ambient Tz = 25◦C, initial of concrete Tp = 25◦C,wooden formwork of 1.8 mm plywood, no insulation, noprotection of top surface; removed in 3 days (72h).
Figure 3: Geometry and �nite element mesh of analysed wall
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
Thermal and moisture analysis
Figure 4: Temperature distribution in the wall [◦C] after 16 hours
Figure 5: Moisture distribution in the wall (x100) after 16 hours
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
Stress analysis
1.2
1.8
2.4
stre
ss [
MPa
]
-1.2
-0.6
0
0.6
0 2 4 6 8 10 12 14 16 18 20
stre
ss [
MPa
]
time [days]
Figure 6: Stress σx in time for cracked (surface) element
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
Stress analysis
(a) at expansion (16 hours) (c) at contraction (4.5 days)
Figure 7: Stress distribution
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
Parametric study of thermal�moisture cracking
(a)XZ=0m (b)YZ=3.5m
(c)XZ=0.35m (d)YZ=10m
Figure 8: Cracking pattern�basic case
Analysed parameters:
1 Tp and Tz
2 time of formworkremoval
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
In�uence of placing and adjoining concrete temp. di�.
(a) XZ=0m (b) YZ=3.5m
(c) XZ=0.35m (d) YZ=10m
Figure 9: Cracking�Tp = Tz = 15◦C
(a) XZ=0m (b) YZ=3.5m
(c) XZ=0.35m (d) YZ=10m
Figure 10: Cracking�Tp = 15◦C , Tz = 25◦C
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
General caseParametric study
In�uence of time of formwork removal
(a) XZ=0m (b) YZ=3.5m
(c) XZ=0.35m (d) YZ=10m
Figure 11: Cracking�removal after 7 days
(a) XZ=0m (b) YZ=3.5m
(c) XZ=0.35m (d) YZ=10m
Figure 12: Cracking�removal after 25 days
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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IntroductionNumerical model
Analysis of RC wallConclusions
Conclusions
Importance
need to ensure desired service life and function of the structure
on-going examination of early-age cracking problem
Numerical model
qualitatively and quantitatively proper results
conformation with present knowledge and experience
Contribution
multi-parameter numerical model of thermal�moisture e�ects inearly-age concrete and its implementation
Barbara Klemczak, Agnieszka Knoppik Early-age thermal�moisture e�ects in RC wall
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AMCM 2011Cracow, 14 June 2011