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PROBABILISTIC MODEL L ING OF CONCRETE STRUCTURES DEGRADATION

Explore the degradation mechanisms of concrete structures over time, including carbonation, chloride ingress, and steel corrosion. Learn about codes and regulations, durability limit states, and a software tool for evaluating degradation models.

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PROBABILISTIC MODEL L ING OF CONCRETE STRUCTURES DEGRADATION

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  1. PROBABILISTIC MODELLING OF CONCRETE STRUCTURES DEGRADATION B. Teplý, P. Rovnaníková, P. Rovnaník, D. Vořechovská Brno University of Technology, Czech Republic REC 2012, Brno

  2. Outline • Degradation of RC structures • …Timeaspect • …Codes and regulations • …Durability limit states • Software tool • Evaluation of somedegradationmodels…Carbonation m. vs. in situmeasurement on coolingtower • …Chloride ingress m. vs. in situmeasurement on bridge in Italy • …Corrosion m. vs. numerical m. • Conclusions

  3. Degradation mechanisms vs. time

  4. Degradation mechanisms vs. time carbonation and/or chloride ingress

  5. Degradation mechanisms vs. time steel depassivation carbonation and/or chloride ingress

  6. Degradation mechanisms vs. time steel depassivation carbonation and/or chloride ingress steel corrosion

  7. Codes and regulations • ISO 13832(2008) • General principles on Design of Structures for Durability • fib Model Code(2010) • Bulletins55, 56 (Firstcomplete draft) • Bulletin 34 Model CodeforServiceLife Design (2006) • EN 206-1(2000) • Concrete – Part 1: Specification, performance, production and • Conformity

  8. Durability limit states 1. Service life format 1a. Simplified/initiation LS 2. Limit state format ULS SLS

  9. Durability limit states Steel depasivation(tini): Steel corrosion(tprop):

  10. Software tool FReET-D probabilistic modeling of degradation processes in timewww.freet.cz (Teplý, Vořechovská,Chromá, Rovnaník – Brno University of Technology) Utilizes probabilistic platform of FReET (Vořechovský, Rusina, Novák – Brno University of Technology) Features: random input variables, MC, LHS, FORM, statistical parameters of result, sensitivity analysis, estimation of probability Pf and reliability index , automatic parametric studies, Bayess updating, number of degradation models

  11. FReET-D: implemented models

  12. Evaluation of carbonation models • Coolingtower(Keršner et al. 1996) • height of 206 m • in-siteinvestigation at the age of 19.1 years • the depth of carbonation measured at 75 locations (on both the internal and external surfaces)

  13. Evaluation of carbonation models Analyticalmodels fibModel Code (Bulletin No. 34) Papadakis et al. (1992), based on massconservation Papadakis et al. (1992), R.H. functionupdated Morinaga (1992), R.H. functionupdated (Teplý et al. 2010)

  14. Evaluation of carbonation models (Vořechovská et al. 2010)

  15. Evaluation of carbonation models (Vořechovská et al. 2010)

  16. Evaluation of chloride ingress models Bridge in Italy Wendner, R., Strauss, A., Guggenberger, T., Bergmeister, K. and Teplý, B., 'AnsatzzurBeurteilung von chloridebelasteten StahlbetonbauwerkenmitBewertung der Restlebensdauer', Beton- und Stahlbetonbau 12/2010 Chloride concentrationmeasured in thedifferentdistancesfromthenearestsurface(from 10 to 50 mm)

  17. Evaluation of chloride ingress models fibModel Code (Bulletin No. 34) fibModel Code; substitutedsurfaceconcentration Crank´ssolution of Fick´s 2nd law Thomas and Baumfort (1999) Nilsson and Carcasses (2004) and Tang and Gulikers (2007)

  18. Evaluation of corrosion model Analytical model(Li et al. 2006) vs. Numerical computation based on nonlinear FE (Vořechovská and Vořechovský 2010)

  19. Evaluation of corrosion model Analytical model (Li et al. 2006) porous zone rust steel concrete crack no corrosion filling of porous zone crack initiation crack on concrete surface, spalling Constant geometry: thick-wall cylinder (Bažant 1979, Pantazopoulou and Papoulia 2001,Tepfers 1979)

  20. Evaluation of corrosion model Numerical model ►ATENA program (Červenka Consulting) ►constitutive model based on smeared crack approach ► used fracture plastic model NLCEM ►expansion of corrosion products: (negative) shrinkage of reinforcement

  21. Evaluation of corrosion model Comparison of models Identical parameters: geometry, E, ft Extras for numerical model: GF, fc,…

  22. Conclusions • Durability design of RC structures is now actual in engineering practice • Durability/performance based approach to the specification of concrete durability may be based on predictive(proven!) models utilization • FReET-D is a software tool for fully probabilistic performance based design; the other proves of the degradation models are needed • FReET-D can be effectively utilized in combination with FReET and ATENA software

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