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VB TECHNICAL UNIVERSITY OF OSTRAVA
FACULTY OF CIVIL ENGINEERING
DOCTORAL DISSERTATION
RELIABILITY OF REINFORCED CONCRETE BRIDGE DECKS WITH RESPECT TO INGRESS OF CHLORIDES
POSUZOVAN SPOLEHLIVOSTI ELEZOBETONOV MOSTOVKY S OHLEDEM K PSOBEN CHLORID
by
Ing. Petr Konen
Supervisor: Prof. Ing. Pavel Marek, DrSc. Ostrava, 2007
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Petr Konen, 2007 Department of Structural Mechanics Faculty of Civil Engineering VB Technical University of Ostrava Czech Republic
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Annotation The aim of the submitted work is to make a probabilistic durability assessment of concrete bridges
affected by deicing agents applied to melt snow. The potential of the application simulation tools,
see SBRA (Based Reliability Assessment method), is studied with respect to chloride ingress
induced corrosion of bridge decks with epoxy-coated steel reinforcement. Representative slabs of
this type are e.g. bridge decks in some parts of the U.S.
The durability of the investigated decks is severely threatened by the risk of corrosion because the
concrete surface is directly exposed to deicing salts. It is necessary to study the effect of cracks in
the reinforced bridge deck which are the most likely gate for chloride ions to enter flaws in
epoxy-coating.
The stochastic approach is applied in the evaluation of the corrosion process in order to respect the
inherent randomness of pertinent random input variables. The Monte Carlo simulation tool is
applied with random variables described by bounded distributions.
Response to the considered loading by chlorides is computed using Ficks second Law of
diffusion. It is expressed by the concentration of chlorides in the most exposed location of the
reinforcement (especially in the epoxy-coating defect). This concentration is compared in the
assessment with the chloride threshold (amount of chlorides sufficient to start corrosion). The
likelihood of corrosion initiation is statistically evaluated and compared with the target probability.
The stochastic model based on the SBRA method utilizes FEM as a transformation model and can
significantly facilitate the study of the significance of input variables with respect to corrosion
initiation. The results indicate that the variation in input parameters substantially affect durability of
bridge deck. The most important variable is diffusion constant. The effect of epoxy-coated
reinforcement improves durability under proper handling and construction practices.
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Anotace Pedloena prce je zamena na pravdpodobnostn posudek trvanlivosti elezobetonovch most
vystavench psoben chlorid. Jsou hledny monosti vyuit simulanch nstroj viz. SBRA
(Simulation-Based Reliability Assessment) pi rozboru trvanlivosti z hlediska vzniku koroze
u mostovky s vztu chrnnou epoxidovm povlakem. Typickm pkladem takovch desek jsou
mostovky realizovan v nkterch oblastech U.S.A.
Trvanlivost sledovanch mostovek je vn ohroena rizikem koroze ocelov vztue vzhledem
k vystaven povrchu betonu pmmu psoben posypovch sol. Je nutn sledovat efekt trhliny
v elezobetonov mostovce usnadujc prnik chlorid k vztui pokozenou epoxidovou
ochranou ocelov vztue.
Pi rozboru koroznho procesu je uplatnno stochastick modelovn zohledujc vstupn nahodile
promnn veliiny. Je uita simulan metoda Monte Carlo a nhodn promnn jsou vyjdeny
useknutmi rozdlenmi.
Jako transforman model k uren odezvy na uvaovan zaten chloridy slou druh Fickv
zkon difuze. Odezva je vyjdena koncentrac chlorid v nejexponovanjch mstech vztue
(zejmna v mstech poruchy epoxidovho povlaku), kter je v posudku porovnna
s tzv. chloridovm prahem, co je koncentrace nutn pro zapoet koroze. Statisticky je
vyhodnocena pravdpodobnost vzniku koroze, kter je porovnna s nvrhovou pravdpodobnost.
Stochastick model na bzi metody SBRA vyuvajc jako transforman model MKP me
vznamn poslouit ke studiu vlivu jednotlivch vstupnch promnnch na trvanlivost z hlediska
rizika vzniku koroze. Z vsledk prce vyplv, e rozptyl vstupnch parametr vznamn
ovlivuje trvanlivost mostovky. Nejzvanj uvaovanou veliinou je difuzn souinitel. Dle se
ukazuje, e kvalitn proveden epoxidov ochrana vztue pozitivn ovlivuje trvanlivost
elezobetnov desky.
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Acknowledgments I would like to take this opportunity to express my gratitude to the many people whose support,
guidance, and assistance made the completion of this thesis possible. First, I owe my greatest
gratitude to my wife Nika, my mother and my family for their continuous support and patience
during my graduate studies.
I would also like to thank professor Pavel Marek, my supervisor. I learned a lot through
collaboration with him and he was always ready to not only discuss research topics but also to share
his experience gained throughout the years. His broad support to young engineers allowed me to
spread the idea of Simulation-Based Reliability Assessment throughout presentations at national as
well as foreign conferences, and allowed me to meet interesting people. He facilitated a bridge
between myself and professor Paul J. Tikalsky, who had invited me to Penn State University.
Professor Tikalsky, who hosted my research visit at Penn State, inspired me to write a thesis on the
topic of stochastic bridge deck performance assessment. Professor Tikalsky originated the idea of
Simulation-Based Reliability Assessment of reinforced concrete structures with respect to cracks
and their interaction with epoxy-coated reinforcement. He gave me helpful advice throughout
interesting consultations. It was also at PSU where I assisted Dave Tepke, Dr. Tikalskys grad
student. He also helped a great deal with my introduction to the field of durability of concrete with
respect to corrosion through long lasting discussions.
In addition, I would like to acknowledge the support of this work that has been provided by
VB - Technical University of Ostrava, Czech Science Foundation (Project No. 103/04/1451 and
No. 103/07/0557), Pennsylvania Department of Transportation, Ministry of Transportation and
Ministry of Education of the Czech Republic (Project MOSTDYN - part SBRA), and Pennsylvania
State University.
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Content Notation............................................................................................................................................... 8
Greek Symbols ................................................................................................................................ 9 Other Symbols................................................................................................................................. 9 Model Variations............................................................................................................................. 9
1. Introduction.................................................................................................................................. 10 1.1 Bridge Decks from Reinforced Concrete ................................................................................ 11 1.2 Effect of Cracks and Epoxy-Coating ...................................................................................... 13 1.3 Reliability Assessment of Bridge Deck .................................................................................. 14
2. Objectives of Thesis ..................................................................................................................... 24 2.1 Scope of Thesis ....................................................................................................................... 24
3. Road Map to Performance-Based Design of Concrete Bridge Decks ..................................... 26 3.1 Random Input Variables.......................................................................................................... 26 3.3 SBRA Analysis ....................................................................................................................... 29 3.4 Reliability Assessment ............................................................................................................ 32 3.5 Durability Assessment............................................................................................................. 33 3.6 Results ..................................................................................................................................... 34 3.7 Summary ................................................................................................................................. 34
4. SBRA Model of Bridge Deck with Crack and Epoxy-coated Reinforcement ........................ 35 4.1 Input Parameters of the Model ................................................................................................ 35 4.2 Transformation Model............................................................................................................. 46 4.3 Monte Carlo Simulation .......................................................................................................... 53 4.4 SBRA Analysis ....................................................................................................................... 54 4.5 Summary ................................................................................................................................. 65
5. Parametric Study .........................
