Sykora & Holicky - Durability Assessment of Large Surfaces… 1 Durability Assessment of Large Surfaces Using Standard Reliability Methods M. Sykora & M. Holicky Czech Technical University in Prague Introduction Measurements Simplified deterioration model Example Conclusions
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Sykora & Holicky - Durability Assessment of Large Surfaces… 1 Durability Assessment of Large Surfaces Using Standard Reliability Methods M. Sykora & M.
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Sykora & Holicky - Durability Assessment of Large Surfaces… 1
Durability Assessment of Large SurfacesUsing Standard Reliability Methods
M. Sykora & M. HolickyCzech Technical University in Prague
IntroductionMeasurements
Simplified deterioration modelExample
Conclusions
Sykora & Holicky - Durability Assessment of Large Surfaces… 2
Cooling tower and its maintenance
Sykora & Holicky - Durability Assessment of Large Surfaces… 3
Steel retaining walls
Sykora & Holicky - Durability Assessment of Large Surfaces… 4
Site measurementsLocal distribution of a carbonation depth
0 12 24
0
0.1
Relative Frequency
n = 74m= 11.05 mmv = 0.31a = 0.59
LognormalGammaNormal
Carbonation Depth [mm]
spatial variation (environmental actions,material properties)?→ discretisation techniques→ simplified approach based on “independent” elementary surfaces
Sykora & Holicky - Durability Assessment of Large Surfaces… 5
Simplified deterioration model- division into zones (similar exposures – splash/upper parts of piers)
- within zones homogeneous random fields W (material properties, concrete cover) + hyperparameters X (single value for whole structure)
- discretization of the zone into N elementary surfaces (random field variables independent)
fib Bulletin 59 Condition control and assessment of reinforced concrete structures
Sykora & Holicky - Durability Assessment of Large Surfaces… 6
Simplified deterioration model
Pf(t) = P{ndeg(t) / N ≥ alim} = EX(t){1 - Fbinom[Nalim, N, pf(W|x(t))]}
- For steel structures the size of an elementary surface may correspond to a size of inspected areas (e.g. 3 m)
- Concrete, chloride ingress ~ 0,5-2 m
The limiting deterioration level alim = 0,1-0,2
alim = 0,15 accepted in the example
pf(∙) is the failure probability of an elementary surface
FORM/SORM
Sykora & Holicky - Durability Assessment of Large Surfaces… 7
Example – carbonation of concretefib Model Code for Service Life Design
Type Variable Symbol Distrib. Unit X VX
Random Concrete cover R Beta mm R 0.35
fields Inverse carbon. resistance
RNAC,0-1 Gamma
(mm2/y.) / (kg/m3)
2e4 0.5
Relative humid. RHreal Beta - 0.71 0.18 Hyper- CO2 concentr. Cs normal kg/m3 8.2e-4 0.12 parameters Model uncert. KS LN - 1 0.1