Numerically and Experimentally Based Reliability Assessment of a Concrete Bridge Subjected to Chloride-Induced Deterioration (original) (raw)
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Structural reliability of concrete bridges including improved chloride-induced corrosion models
Structural Safety, 2000
A structural deterioration reliability (probabilistic) model has been used herein to calculate probabilities of structural failure. New reinforced concrete corrosion initiation, corrosion rate and time-variant load models are proposed. Three durability design speci®cations are considered in a lifetime reliability analysis of a RC slab bridge. Time-variant increases in loads are considered also. It was found that the application of de-icing salts causes signi®cant long-term deterioration and reduction in structural safety for poor durability design speci®cations. A reduced cover or increased water-cement ratio increases failure probabilities. When compared to the case of``no deterioration'', it was observed also that the probability of failure only marginally increased for good durability design speci®cations. The approaches described herein are relevant to other physical infrastructure also. #
Life-Cycle Performance of Deteriorating Structures, 2003
This paper presents a probabilistic approach for predicting the chloride contamination of concrete and reinforcing steel corrosion, which takes into account the uncertainty associated with the analytical models of chloride transport, corrosion initiation, as well as damage accumulation, material properties, structural dimensions, and applied environmental and mechanical loads. The proposed approach is illustrated on an aging reinforced concrete bridge deck that has been exposed to chlorides from deicing salts for forty years. An extensive non-destructive and destructive evaluation of the corrosion-damaged deck was undertaken. The field survey data showed a considerable level of variability in all parameters measured with coefficients of variation ranging from 34% for the concrete cover depth to 86% for the diffusion coefficient. The distributions of the chloride concentration at the level of the top reinforcement mat and the time for its corrosion initiation were generated using Monte Carlo Simulation. The simulated results were very close to the field data, which illustrates the prediction capabilities of probabilistic methods as opposed to deterministic methods.
Probabilistic modeling of chloride contamination and corrosion of concrete bridge structures
Fourth International Symposium on Uncertainty Modeling and Analysis, 2003. ISUMA 2003.
This paper presents an approach to the uncertainty modeling and analysis of chloride contamination of concrete and corrosion of reinforcing steel of highway bridge structures that are subjected to the damaging effects of chlorides from deicing salts. The statistics of the governing parameters are generated from a field survey of an aging bridge structure that was exposed to the contaminants for about forty years. The uncertainty analysis and prediction of chloride concentration and reinforcement corrosion is carried out using the direct Monte Carlo method. The model predictions agree very well with the field data, which illustrates the capability of a probabilistic model to quantify the actual condition of a deteriorated structure.
Maintenance Strategies Based on the Assessment of Chloride Induced Deterioration
2011
The maintenance of an adequate safety level of concrete bridges under their gradual degradation due to traffic and environmental actions during service life is an expensive, problematic and questionable task. Chloride ion ingress is an important aspect of durability design and maintenance, especially in regions where winter salt application for traffic safety is common, e.g. highway bridges. Based on a case study of the Neumarkt Bridge, Italy, a feasible approach to analyze possible chloride induced deterioration illustrated will be presented. Based on laboratory analyses of specimens the chloride surface concentration was inversely determined and used for the prognosis of the corrosion propagation over time. This information served as basis for a performance assessment with respect to code based service and ultimate limit states resulting in an estimation of the remaining service life and discussion of feasible maintenance strategies.
Evaluation of Time-dependent Chloride Parameters for Assessing Reinforced Concrete Bridges
proceedings of the 6th International Conference on Bridge Maintenance, Safety and Management (IABMAS), 2012
Chloride diffusivity of concrete is an important input parameter in service life prediction models. Diffusion coefficient is influenced by mix proportions, curing, compaction, pore size distribution, time, relative humidity and temperature, and decreases over time. However, many life time prediction models still consider this parameter as a constant, resulting in overly conservative durability designs, especially when GGBS or Fly ash are present in concrete mix. Some of the models proposed so far for estimating this parameter are time-dependent, while others are based on mix proportions. A laboratory program is reported, and a novel numerical model is sought for to estimate the degree of hydration as determined from the heat of hydration of concrete. Diffusion coefficients are measured using Nordtest rapid migration test; and a correlation is sought for, between the two. Tests are performed at regular intervals to allow for characterization of the influence of the aforementioned parameters.
System Reliability of Bridge Structure Subjected to Chloride Ingress
Proceedings of the Joint COST TU1402 - COST TU1406 - IABSE WC1 Workshop: The Value of Structural Health Monitoring for the reliable Bridge Management, 2017
The parameters relevant for prediction of service lifetime with respect to chloride ingress are associated with large uncertainties. Full-scale measurements are in demand for conditions which are as homogeneous as possible. The present paper first summarizes statistical distributions which are obtained based on measurements from the Gimsøystraumen bridge in Norway. A large number of chloride profiles are available, and for each of these the diffusion coefficient and surface concentration (due to sea-spray) are estimated. Extensive measurements of concrete cover are also performed. These probability distributions are subsequently employed as input to a prediction model for chloride concentration at the steel reinforcement for a single but arbitrary position along the reinforment. Since the input parameters are represented in probabilistic terms, the chloride concentration is also a stochastic quantity. Furthermore, introducing the critical chloride concentration on a similar form, the probability of exceeding the critical threshold is determined as a function of time. In order to address chloride attack on the entire bridge, a system model with 90 components is next introduced. This model is employed in order to perform reliability updating based on observations at a number of sites along the bridge. First-order (FORM) reliability methods typically become inaccurate for large systems of this type. Crude Monte Carlo Simulation (which can be more accurate) will easily demand impractical efforts in terms of CPU-time, and a more efficient Monte Carlo simulation method is accordingly applied. It is shown that this typically reduces computation times by a factor of around 10.
Cement and Concrete Composites, 2012
Concrete structures are subjected to chloride-induced corrosion that can lead to shortened service life. Reliable predictions of life cycle performance of concrete structures are critical to the optimization of their life cycle design and maintenance to minimize their life cycle costs. This paper presents two simplified semi-analytical probabilistic models based on the first-and second-order reliability methods to model the uncertainty of the key parameters including surface chloride concentration, chloride threshold, cover depth and diffusion coefficient, which govern the chloride ingress into concrete and corrosion of reinforcing steel. A case study of a reinforced concrete highway bridge deck is used to illustrate the capability and efficiency of these simplified probabilistic models in modeling the uncertainty and predicting the time-dependent probability of corrosion. The models enable to quantify the impact of the different governing parameters on probability of corrosion and service life, which can be used to develop costeffective management strategies.
Structures, 2020
Deterioration of RC bridges due to chloride induced corrosion is a grave concern worldwide. It occurs essentially, when the reinforcement embedded in concrete is exposed to marine or aggressive environments. Over the past few decades, many studies aimed at determining the parameters influencing the service life of structures affected by reinforcement corrosion. The aim of the present work is to put forward a reliable and simple service life model for predicting the useful life or period of RC bridges affected by chloride ingress and to validate the output of the model with the deterioration of an existing RC bridge structure. The application of the service life model has been done in an Indian bridge in the context of coastal environment. Parametric studies have been conducted in the model for examining the effect of various parameters such as water-cement ratio, reinforcement diameter, cover thickness, type of binder and corrosion rate on the variation of service life of the RC bridge structure. The results of the parametric study explained in a detailed manner so as to get an actual insight of the structural degradation mechanism for structures exposed to chemically aggressive environments.
Modeling of Chloride Concentration Effect on Reinforcement Corrosion
Computer-Aided Civil and Infrastructure Engineering, 2009
The corrosion of reinforcement is one of the major causes of deterioration of reinforced concrete (RC) structures, considerably affecting their durability and reliability. The rate of reinforcement corrosion is governed by, among other factors, the presence of chlorides on the surface of the steel. The assessment of such deteriorating effects necessitates the development of relevant models and the utilization of advanced simulation techniques to enable the probabilistic analysis of concrete structures. In this article an approach for the assessment of the durability and reliability of RC structures under attack from chlorides is introduced. The field of chloride concentration at different locations in the structure (represented in 2D space by chosen longitudinal or cross sections) is modeled as a function of time by a cellular automata (CA) technique. The results of this simulation are then utilized for the assessment of a steel corrosion prognosis using a probabilistic 1D model at chosen points, although the rate of corrosion is based on experimental results. The concentrations of chlorides and pH levels are reflected in this way. The described approach is applied to an illustrative example showing the feasibility of capturing the effect of chloride concentration on the steel
A study of chlorides in a reinforced concrete bridge
The current study investigates chloride deterioration of a 100 year old bridge located in a harsh marine environment. Constructed in 1908 -1909 the Mizen Head Footbridge was one of the oldest reinforced concrete bridges in Ireland. The demolition of the bridge in 2009 provided a unique opportunity to examine its service life and to extract samples for analysis and investigation. Reinforcement corrosion due to chloride attack was identified. A focused study indicates that chloride contaminated constituents may have been used in the concrete mix. This research may provide valuable advice and guidance for the asset management of similar structures.