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Reliability of Reinforced Concrete Structures Subjected to Corrosion-Fatigue and Climate Change Emilio Bastidas-Arteaga

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Reliability of Reinforced Concrete Structures Subjected to Corrosion-Fatigue and Climate Change Emilio Bastidas-Arteaga Reliability of Reinforced Concrete Structures Subjected to Corrosion-Fatigue and Climate Change Emilio Bastidas-Arteaga To cite this version: Emilio Bastidas-Arteaga. Reliability of Reinforced Concrete Structures Subjected to Corrosion-Fatigue and Climate Change. International Journal of Concrete Structures and Materials, springer, 2018, 12 (1), 10.1186/s40069-018-0235-x. hal-01698136 HAL Id: hal-01698136 https://hal.archives-ouvertes.fr/hal-01698136 Submitted on 31 Jan 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. International Journal of Concrete Structures and Materials DOI 10.1186/s40069-018-0235-x ISSN 1976-0485 / eISSN 2234-1315 Reliability of Reinforced Concrete Structures Subjected to Corrosion-Fatigue and Climate Change Emilio Bastidas-Arteaga* (Received November 26, 2016, Accepted January 7, 2018) Abstract: Durability of reinforced concrete (RC) structures is affected by certain environmental conditions and operational actions which can reduce their lifetime significantly. Among these actions, this paper proposes a stochastic model that accounts for the combined effects of chloride-induced corrosion, climate change and cyclic loading. Separately, corrosion leads to cross-section reduction, climate change produces changes in temperature and humidity and fatigue induces nucleation and propagation of cracks in the rebars. When considered together, pitting corrosion nucleates cracks while environmental factors affect the kinematics of chloride ingress and corrosion propagation. The proposed approach is illustrated with the reliability analysis of a bridge girder subjected to cyclic loading under various environmental conditions. The overall results indicate that climate change effect induces lifetime reductions ranging between 1.4 and 2.3% if fatigue load is neglected. Under cyclic loading, total lifetime reduction increases up to 7%. Keywords: reliability, corrosion-fatigue, reinforced concrete, climate change, chloride ingress. 1. Introduction a period of continued service (Bastidas-Arteaga et al. 2009; Bastidas-Arteaga and Schoefs 2015; Clifton 1993; Mori and Reinforced concrete (RC) civil infrastructure systems are Ellingwood 1995). critical assets for the socioeconomic development of any This paper focuses on a combined corrosion-fatigue dete- country. Designing and maintaining these systems for a rioration mechanism. Corrosion is induced by chloride pen- particular service lifetime have been recognized as critical etration that results in turn from a complex interaction issues worldwide. RC structures are characterized by high between physical and chemical processes that are driven by durability; however, during their operational life, they are environmental surrounding conditions (Bastidas-Arteaga and subjected to internal and external actions that affect perfor- Stewart 2016;Nguyenetal.2017;Saettaetal.1993). Com- mance, serviceability and safety (Imam et al. 2015; Kim bined corrosion-fatigue deterioration results from the action of et al. 2016; Marquez-Pen˜aranda et al. 2016; Morga and cycling stresses in corrosive environments. Localized corro- Marano 2015;Sa´nchez-Silva and Klutke 2016). Nowadays, sion leading to pitting may provide sites for fatigue crack many deteriorated structures are evaluated for possible repair initiation. For example, several experimental studies have and continued service because their replacement would be shown that pitting corrosion has been responsible for the economically unfeasible. For example, about 173,000 nucleation of fatigue cracks in a wide range of steels and bridges in the United States are structurally deficient or aluminum alloys (Ahn et al. 1992; Chen and Duquette 1992; functionally obsolete due in part to corrosion (Bhide 1999; Kondo 1989). Corrosive agents (e.g., seawater) increase the Pritzl et al. 2014; Radlin´ska et al. 2014). Regarding costs, fatigue crack growth rate (Gangloff 2005), whereas the mor- Koch et al. (2016) reported that the global cost of corrosion phology of metals/alloys at micro-level governs the pit is US$2.5 trillion (about 3.4% of the global Gross Domestic nucleation sites (Rajasankar and Iyer 2006). Product). Thus, developing robust models for prediction and There exists a limited amount of experimental tests on strategies for periodic inspection and maintenance plays a corrosion-fatigue in RC structures. Ahn and Reddy (2001) significant role in enabling target reliabilities to be met over performed an experimental study to evaluate the durability of RC beams subjected to fatigue loading and chloride ingress. The tests included 16 beams and accounted for the UBL, Universite´ de Nantes, GeM, Institute for Research influence of static and cyclic loading for different water/ in Civil and Mechanical Engineering/Sea and Littoral cement ratios. Alternate filling and draining of a tank sim- Research Institute, CNRS UMR 6183/FR 3473, 2 rue de ulated the marine tidal zone, and a galvanostatic corrosion la Houssinie`re, BP 99208, 44322 Nantes Cedex 3, France. technique was used to accelerate corrosion of the rein- *Corresponding Author; forcement. The ultimate strength of the beams was tested E-mail: [email protected] after 78,000 cycles by applying four-point flexural loading. Copyright Ó The Author(s) 2018. This article is an open The results indicated that beams subjected to cyclic loading access publication during the exposure period showed lower ultimate strength process during the stages of pit-to-crack transition and crack than those subjected to static loading. Taking into account growth. Based on the previous considerations, the corrosion- the imminent reduction of ultimate strength, other experi- fatigue process is divided into three stages: (i) corrosion mental studies focused on estimating the effectiveness of initiation and pit nucleation, tcp; (ii) pit-to-crack transition, using composite repair materials (Al-Hammoud et al. 2011; tpt; and (iii) crack growth, tcg. ElSafty et al. 2014; Masoud et al. 2005; Song and Yu 2015). The proposed deterioration model does not account for the More recently, Wang et al. (2018) performed a comprehen- loss of adhesion at the steel/concrete interface caused by sive experimental study to quantify the effects of cyclic load corrosion propagation as well as the effect of permanent on the chloride ingress process. They found that considering charges on the long-term mechanical behavior. Further fatigue loading conditions have important effects in lifetime model developments will be necessary in the future to assessment depending on the aggressiveness of the sur- integrate these aspects and improve lifetime assessment. rounding environment. Modeling the combined effect of corrosion and fatigue 2.1 Corrosion Initiation and Pit Nucleation remains still an open challenge. Bastidas-Arteaga et al. This stage is divided into two sub-stages: (i) time to cor- (2009) proposed a first probabilistic corrosion-fatigue model rosion initiation, tcini, and (ii) time to pit nucleation, tpn. The for RC structures subjected to chloride ingress; however, this first sub-stage encompasses the time from the end of con- model uses a simplified solution of Fick’s law to simulate the struction until corrosion begins. For the assessment of tcini, chloride ingress process that does not always represent this section presents a formulation for chloride ingress reality. On the other hand, experimental evidence indicates modeling that considers the interaction between three that the chloride ingress is highly influenced by the weather physical problems: chloride ingress, moisture diffusion and conditions at the surrounding environment—i.e. temperature heat transfer. Each phenomenon is represented by a partial and humidity. Since climate change studies predict several differential equation (PDE) expressed in the following gen- changes in the climate (IPCC 2013), the impact of global eral form (Bastidas-Arteaga et al. 2011): warming on chloride ingress, and therefore on structural ow reliability, should be also considered in the assessment of the f ¼ divJ þ divJ 0 ð1Þ ot |ffl{zffl} |ffl{zffl} structural behavior. diffusion convection Within this context, the main goal of this paper is to improve the model proposed by Bastidas-Arteaga et al. where w represents the studied parameter (chloride concen- (2009) to be able to consider the influence of realistic tration, relative humidity content or temperature), t is the exposure conditions (including climate change) on failure time period and the correspondence between f, J, J0 and the probability. To accomplish this objective, the proposed terms for the physical problem is presented in Table 1. lifetime prediction approach includes a numerical solution For chloride ingress, Cfc is the concentration of free * * for the transport governing equations in the assessment of chlorides, h is the relative humidity and Dc and Dh represent the corrosion initiation time. the apparent chloride and humidity diffusion coefficients, The paper starts describing the deterioration model used to respectively: combine the
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