Meta-model for the assessment of soilstochastic properties from monitering:
application to harbor structuresKhanh Toan Le, Franck Schoefs, Francesca Lanata
UMR CNRS 6183
1. Objective and methodology
2. Presentation of the studied structure
3. Random variables and probabilistic modeling
4. Calibration for response surface
5. Identification results
6. Conclusion and perspectives
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
1. Identify parameters of soil characteristics from StructuralHealth Monitoring data (SHM)
2. Developp a Response Surface based inverse analysis
3. Provide pdf of soil parameters for structural reliability
Objective and methodology
Structural model
Random loading(here tide and water
level)
Random behavior(materials)
Responses:+ Displacement
+ Stress
Measured loading
Inverse analysis RS model
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
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Numericalsituations for
external loading
Set of a priori parameters
Numericalresponse
Meta-model calibration
Inverse analysis
Random parametersidentified
Verification, validation
FEM solving(Numerical data base)
Polynomial Response Surface
Objective function
Measureddata
Objective and methodology 31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
Presentation of the studiedstructure
Cheviré 4
• 12 monitored tie-rods (30%)–Technology : electricalstrain gauges
• 3 piezometers ; measure of underground water level
• Data collection every 30 minutes
• Duration of collection : 01/2004-6/2005Strain gauge
Cross section of the wharf Cheviré-4 View of the instrumentation plan
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
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Random variables and probabilistic modeling
Elements of wharf modelled under PLAXIS (FEM code)
Calculated parameters of soil:
1. γsat : Own weight satured
2. γunsat : Own weight unsatured
3. E: Young modulus
4. φ : Frictional internal angle
5. ν : Poisson modulus
6. c : Cohesion.
7. ψ : Dilatancy angle
Selection of set of a priori parameters
Water level of the tide measureduring the two years
Sand: γunsat = 19kN/m3; E=30Mpa; φ =30 ; ν=0; ψ=0
I. Selection of set of a priori parameters
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
Selected phases of water level during a tide, CMAR=69
II. Sensibility analysis of parameters of soil to theloading in the tie-rod
Sensitivity analysis: influence of parameters of soil in the response
CMAR: in France, theoscillation amplitudeof semi-diurnal tide isassociated to acoefficient named tidecoefficient .
III. Construction of a numerical data base
450 (to 600) computations byPLAXIS are performed
A numerical data base of 450 (to 600) resultscalculated of the loading in the tie-rod
Random variables and probabilistic modeling
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
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Calibration for response surface I. Selection of input random variables forthe response suface calibration
6 input variables 28 terms in the expression of SRReduction of
variable
2 variables
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
II. Quadratic response surfaces
Full quadratic
Linear
Pure quadratic
Linear withinteraction
Calibration of response surface 31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
• ICDS1
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III. Response Surface Selection
Residual values criteria for each type of RS
Representation of loading calculed in the tie-rod by RS and Plaxis
Calibration for response surface 31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
Identification resultsI. Identification Methodology
Objective fonction and least squares method
II. Results
Identification result X1 et X2
31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
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Identification: results for X1 et X2
II. Results
Parameters of distribution of X1 et X2
Identification results 31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
III. Verification and validation
Evolution of loading in the tie-rod T4 (2004/2005)
Identification results 31st May - 1st June 2012, Lisbon Portugal
Durable StructuresFrom construction to rehabilitation
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
• ICDS1
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Conclusion and perspective
I. Conclusions
1. A probabilistic model suggested: Quadratic Response Surface foridentifying mechanical parameters of embankment from Structural HealthMonitoring data .
2. Research shows the good accuracy of RS meta-model in comparison to EFmodel. Accuracy of the modeling.
3. Identification result of frictional internal angle shows that support of thedistribution contains acceptable values in comparison to littérature.Physical sense of the modeling.
4. Suggested model allows to extrapolate results for tide coefficients verydifferent from a numerical data base. Robustness of the modeling
5. Reduction of numerical calculation time. Tractability of the modeling
6. Reduction of number of input random variables.
7. Capacity of application for different behavior models
II. Perspectives
1. Identification of another parameters: γ, E.
2. Analysis of structural reliability for in service structures.
3. Consideration for structures submitted to various loading: moorings,berthings, wind...
THANK YOU FOR YOUR ATTENTION!
ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012
LNEC
• ICDS1
2