/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1016/S0045-7949(01) Computers and Structures, 79, 13, pp. 1251Structures, 79, 13, pp. -1264Structures, 79, 13, pp. , 2001 ON M5S 1A4, Canada, tel: (416) 978-6238, e-mail: thomas@civ.utoronto.ca ABSTRACTTo calculate the service life of reinforced concrete (R.C.) structures, the process of reinforcement corrosion was modeled using a numerical formulation of the associated mass transport partial differential equations (PDE's). Migration of chlorides, moisture and heat transfer within concrete, resulting from seasonal variations in the surface conditions of the R.C. member, form a coupled boundary-value problem, which was solved in space using a finite element formulation and in time using a finite difference marching scheme. The stage of active corrosion was modeled by including in the numerical algorithm of the F.E. formulation the mass conservation equation that describes diffusion of oxygen in the concrete cover. The paper presents details of the F.E. formulation and computed results from selected case studies.Keywords: Corrosion; far field boundary; finite elements; Galerkin formulation; heat transfer; mapped infinite elements; mass transport. * Corresponding Author DEFINITION OF THE ASSOCIATED PHYSICAL PROBLEMThe service life of reinforced concrete highway structures is often limited by chloride-induced corrosion of the reinforcement, due to exposure to marine environments or to de-icing salts that are routinely used in the winter. Corrosion leads to loss of reinforcement section, loss of steelconcrete bond and delamination of the concrete cover with detrimental consequences on the load carrying capacity of the structure.In general, concrete protects embedded reinforcing steel against corrosion by providing a highly alkaline environment (pH>13.0) that maintains the steel in a passive state. The concrete cover also serves as a physical barrier against the ingress of aggressive species that are necessary to initiate and sustain the process of corrosion. In the literature, corrosion of steel in concrete is usually idealized as a sequence of two separate phases: initiation and propagation of the chemical process (Fig. 1, [1]). During initiation chlorides migrate from the surface of the member through the concrete cover to the steel reinforcement. When their concentrati...
This paper presents the results of using distributed Brillouin fibre sensors to detect crack formation in a simply supported reinforced concrete beam subjected to four-point loading. A Brillouin multiple-peak fitting method was used to enhance the spatial and strain resolutions of the measurements. By doing this, the distributed strain profile along the beam was determined with a 5 cm read-out resolution in comparison with the 15 cm spatial resolution of the fibres. The location of the cracks was identified by locating the positions in the strain profile where the strain suddenly changes, by searching for the maximum compressive or tensile peaks in the Brillouin frequency spectrum, as opposed to conventional strain reading, which focuses solely on the maximum Brillouin peak. The amplitude of the Brillouin peak for the suddenly changed strain (crack) was found to be smaller than half of the amplitude of the maximum Brillouin peak at the maximum strain location corresponding to the average strain of the material, which would have been neglected by standard peak or area fitting methods, especially for fine cracks or the initial crack build-up period.
Corrosion of reinforcing steel in reinforced concrete (RC) infrastructure is one of the most detrimental deterioration mechanisms, affecting both safety and serviceability. In the present study, a comprehensive analysis methodology of corrosion damage is adopted. The detrimental effects of corrosion‐induced degradation of material properties on the ultimate capacity of an existing aging RC bridge pier under concentric loading are investigated. A three‐dimensional nonlinear finite element analysis using the commercially available finite element program DIANA is used. The main corrosion‐induced deteriorating factors considered in the present study are: concrete strength degradation within the cover and part of the confined concrete core due to corrosion‐induced cracking, degradation of confinement effects, steel area reduction due to uniform corrosion (in both longitudinal and tie reinforcement), steel ductility degradation due to pitting corrosion, buckling of compressive steel bars due to cross‐section reduction and confinement degradation, and bond strength degradation between steel and concrete induced by concrete cracking/spalling. The methodology is evaluated by comparing the numerical results to those of corroded column tests reported in the literature.
A reliable assessment of the performance of reinforced concrete structures affected by reinforcement corrosion requires a through understanding of both material deterioration and its impact on structural behaviour in order to evaluate its safety and serviceability, in addition to estimating its remaining life. This paper presents an approach for service life prediction of reinforced concrete structures exposed to chloride environments that combines a finite element modeling of the chloride transport and a reliability-based analytical model for onset of damage and its accumulation. Service life is defined as the time until damage accumulation reaches an unacceptable level or 'limit state'. The approach used here combines analytical models of the actual physical deterioration mechanism and mechanical damage build-up with probabilistic methods to obtain a reliable quantitative estimate of the remaining life of deteriorating structures. The considerable uncertainties associated with the parameters that govern the buildup of corrosion-induced damage are modeled as random variables. By using Monte Carlo simulation, the probabilistic distributions of the chloride penetration front and corrosion initiation time are generated. The proposed approach is illustrated on a reinforced concrete bridge deck exposed to chlorides from de-icing salts.
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