Reliability of linear structures - Latest advances and challenges from a European perspective

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Leichtweiß-Institute for Hydraulic Engineering and Water ResourcesDepartment of Hydromechanics and Coastal Engineering

Marie Naulin, Andreas Kortenhaus & Hocine Oumeraci | 9 December 2011 | FRMRC Science of Asset Management Workshop | SAM 2011 | London

Reliability of linear structures - Latest advances and challenges from a European perspective

9 December 2011 | Naulin et al. | Reliability of linear structures |

Contents

Motivation

Reliability analysis - Latest advances in XtremRisK project Introduction Reliability analysis of sea dikes, coastal dunes & flood defence walls Time dependency

Further research projects incl. reliability aspects in Europe Future challenges


North Sea Flood of 1962, Hamburg, Germany


Legal Background

European Flood Directive (2007/60/EC)

Directive on “the assessment and management of floods”

Required steps of the member states: Preliminary flood risk assessment

(22 Dec 2011) Flood hazard and flood risk maps

(22 Dec 2013) Flood risk management plans

(22 Dec 2015)


German Joint Research Project “XtremRisK” Development of methods to perform an integrated risk analysis based on the

"Source-Pathway-Receptor - concept “ for open coasts and estuaries exposed to extreme storm surges

Analysis of current (2010) and future (2100) scenarios Term of project: 2008 – 2012 Partners: three German universities, local authorities & other consulting partners

area at risk flood defence structuresstorm surge

Source Pathway Receptor Extreme storm surges Flooding probability

Vulnerability assessment(tangible/ intangible)

Integration (Risk analysis, risk evaluation and risk management)


Overview of Subproject 2 (Risk Pathway)

Objectives Analysis of the loading and reliability of coastal flood defence

structures under extreme storm surges

Methodology Reliability analysis of flood defences Breach modelling of dikes and dunes

Results Failure probabilities Pf of the flood defence systems Initial flooding condition due to wave overtopping/ overflow

and / or breaching results will used for inundation modelling of the hinterland and

for integrated flood risk analysis


Input Data by Subproject 1 (Risk Source) Empirical and statistical analysis of observed water level gauges Parameterization of storm surges and development of a storm surge generator Multivariate statistical assessment of the storm surge curves using the parameters

‘highest turning point' and ‘fullness‘ Joint exceedance probability Pe

Source: Wahl et al. (2010)

Time

Sea level

S

f(x)

2

1

t

t

dxf(x)F

t1 t2

NN

Definition: „Fullness“


b) Failure mechanisms and limit state equations (LSE): z = R – Sz < 0: failure, z > 0: no failure

Reliability Analysis of Flood Defences

LSE Wave Overtopping/Overflow z = qadm - q

c) Uncertainties, calculation of failure probabilities

a) Description of flood defence system

d) Fault tree analysis

Dike Mobile flood wall

Storm surge barrierFlood wall

Wave Overtopping

Overflow

q

q


Failure Mechanisms of Sea Dike

waves andwater levelat structure

overflowovertopping

Failure mechanisms at landward slope• Velocity wave

overtopping• Velocity overflow• Erosion (grass,

clay, sand)• Sliding of clay layer• Uplift of clay layer• Deep slip (Bishop)• Breach

developmentgeometry and soil parameters of the dike

Failure mechanismsin the dike• Piping• Matrix erosion• Sliding

LOADING

RESISTANCE

loading at structure

Failure mechanismsat dike top• “Kappensturz”

Non-structuralfailure mechanisms• Wave overtopping• Overflow

Failure mechanismsat seaward slope• Wave impact• Velocity wave run-up• Erosion (grass, clay,

sand,)• Instability revetment• Uplift revetment• Deep slip (Bishop)• Breach development


Overview of General Fault Tree for Sea Dikes

TOP Flooding of Hinterland

Dike Breach

Failure Seaward

Slope

Failure Landward

Slope

Failure Inner DikeLSE Over-

toppingLSE

Overflow

Failure Dike Top

OR

OR

OR

LSE 1 LSE m

OR

LSE 1 LSE n

OR

LSE 1 LSE o

OR

LSE 1 LSE p

OR

Non-Structural

Failure

LSE = limit state equation


Failure Mechanisms of Coastal Dune

waves andwater levelat structure

overflowovertopping

Failure mechanisms at landward slope• Overwash• Breach

geometry and soil parameters of the dune

LOADING

RESISTANCE

loading at structure

Non-structuralfailure mechanisms• Wave overtopping• Overflow

Failure mechanismsat seaward slope• Erosion


Overview of General Fault Tree for Coastal Dune


LSE Overwash

LSE Breach

LSE Over-topping

LSE Overflow

OR

OROR

Non-Structural

FailureStructural

Failure

LSE developed for dikes

LSE Erosion

LSE = limit state equation


Overview of General Fault Tree for Flood Defence SystemR

iver

Estuary

flood defence system with flood threat from sea and river (e.g. estuary)

Dike

Flood wall

Lock

Protected area

Dune

Riv

er d

ike

(leve

e)

Sea

Sea


OR

River dike Lock Dune Flood

wall

OR

Dikesection 1

Dike

Dikesection n

* * * *

Dike Breach

Non-Structural

Failure

*OR

* *


Time Dependency

detoriation

detoriation

Legend


Adjustments of Limit State EquationsExample: LSE for wave overtopping and overflowLSE compares overtopping/overflow rates of flood defence structure:

Where:qadm = admissible overtopping rate [m³/s/m]q = actual overtopping rate [m³/s/m] mean overtopping/ overflow rate

total overtopping/ overflow volume

q

q

V(t)

AdjustmentLSE compares total overtopping/overflow volumes of flood defence system:

Where:Vadm = admissible overtopping/overflow volume [m³]V = actual overtopping/overflow volume [m³]

z = qadm – q

z = Vadm – V


Research Projects incl. Reliability Aspects at TU BraunschweigRecent:

• FLOODsite (EU) Integrated Flood Risk Analysis and Management Methodologies

Ongoing:

• XtremRisK Extreme storm surges at open coasts and estuarine areas - Risk assessment and mitigation under climate change aspects

• NTH BAU – SP4 A risk-based strategy for monitoring, inspection and maintenance of coastal protection structures as an integral part of life cycle calculation and optimization processes

• COMTESS Sustainable coastal land management – trade-offs in ecosystem services

• ProMoHaImplementation of probabilistic calculation of estuary sea dikes in Hamburg, Germany

• Falster DikeImplementation of probabilistic calculation of sea dikes and coastal dunes in Falster, Denmark


Selection Research Projects incl. Reliability Aspects in EuropeRecent:

ComCoast (EU), FLOODsite (EU), SafeCoast (EU), RIMAX (DE)

Ongoing:

• BaltCICA Climate Change: Impacts, Costs and Adaptation in the Baltic Sea Region (EU)

• CRITERRE Application of geophysics to levee assessment and ERINOH National research project on internal erosion (FR)

• FloodControl2015 / SBW Solutions for smart flood control (NL)

• FloodProBE – WP3 Reliability of urban flood defences (EU)

• FRMRC Flood risk management research consortium (UK)

• HoRisK Flood risk management for coastal areas (DE)

• LDA / TOI Levee Design and Assessment (NL) • THESEUS Innovative technologies for safer European coasts in a changing climate (EU)


Some Future Challenges

Mean sea level rise Increased storminess Transitions Length effects Time dependence Flood defence systems Single point structures Human and organisation

errors (HOE) ...

Time dependence

TransitionsMean sea level rise

HOE

FloodControl 2015

Church & White (2006)


ContactMarie Naulin

Leichtweiß-Institute for Hydraulic Engineering and Water ResourcesDepartment of Hydromechanics and Coastal Engineering

TU BraunschweigT: +49 531 391-3937F: +49 531 391-8217

E: [email protected]

tremRisKXwww.xtremrisk.de

Thank you for your attention!

Reliability of linear structures - Latest advances and challenges from a European perspective

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