外文资料翻译--温度和相对湿度对沿印度海岸的钢筋混凝土构件腐蚀起始时间的影响.doc

毕业设计(论文)外文资料翻译学 院： 建 筑 工 程 学 院 专 业： 土 木 工 程 姓 名： 学 号： 外文出处： International Journal of Reliability, Quality and Safty Engineering Vol 15,No.6(2008)539-553 World Scientific Publishing Company 附 件： 1.外文资料翻译译文；2.外文原文。指导教师评语： 签名： 年 月 日附件1：外文资料翻译译文国际期刊上发表的可靠性、质量和安全工程第15卷，第6号（2008）539-553世界科学出版社温度和相对湿度对沿印度海岸的钢筋混凝土构件腐蚀起始时间的影响 一种概率的方法SATISH.B.ALLAMPALLEWARA.SRIVIDYA摘要：由氯离子引起的部分饱和混凝土构件的钢筋混凝土腐蚀的起始时间在印度海岸的五个地方处于调查，运用简化概率分析和研究钢筋锈蚀的参数灵敏度。提出了使用一种基于扩散之前入口模型表面氯浓度和变量不断扩散的系数。当钢筋表面的氯离子浓度超出了某一临界值腐蚀才开始。在模型中考虑的各种各样的输入参数都是表面氯浓度(Cs)、氯化物阈值（Cth）钢筋混凝土保护层（X）、参考扩散系数(Dref)、年龄(t)、引用年龄(tref)、扩散腐烂指数(m)和每月的温度和相对湿度校正因子f(t)和f(h)来引用扩散系数。为了预测腐蚀的起始时间，使用了印度计量部门所收集的温度和相对湿度数据，并且所有其他参数假定相同。在腐蚀起始时间中发现了一个大的变化，因此在一个地区考虑温度和相对湿度数据是有必要的。在生活中只考虑了完全饱和条件下的混凝土并因此低估了一个钢筋混凝土构件腐蚀的起始时间。确定方法使用参数平均值，并提供一个50%的初锈概率，但概率方法为选定的腐蚀风险提供开始腐蚀的预测时间，并提出了腐蚀的概率参数灵敏度。腐蚀起始时间依次在Colaba、Kanyakumari、Santacruz、Chennai 和 Vishakhapatnam 发现。腐蚀起始时间对业主、设计师或者对及时作出维修优先权、维修策略、腐蚀防护，以优化维护计划和预算的组织是有用的。在最佳时间，有计划的维修是最安全、最具性价比的方法。关键词：蚀性；部分饱和混凝土；氯离子进入；扩散过程；温度；相对湿度；概率；灵敏度。1. 引言钢筋混凝土结构在世界各地使用最广泛。钢筋混凝土结构在腐蚀性的环境中随时间恶化，影响美学、功能和结构方面的服务。恶化的速率取决于一些因素，如规划、设计、施工、运行和使用、维护。混凝土的降解与其耐久性和钢筋的腐蚀有关。钢筋的腐蚀导致混凝土构件通过开裂、分层和剥落混凝土保护层、降低混凝土及钢筋截面、钢筋与混凝土粘合强度的减弱、强度和延性的降低而断裂，将导致结构不可挽回的损失和倒塌。因此，混凝土结构的安全性和适用性在服务中需要被考虑。碳化、硫酸盐和氯攻击、钢锈蚀可能会引起钢筋混凝土构件和建筑的降解。氯作用引起的钢筋锈蚀(氯离子渗透进入混凝土)被认为是不同混凝土结构恶化的主要原因之一(如：桥梁、海岸结构和停车场)。氯的来源有水、化冰盐和海洋环境中的空气。一旦氯离子在钢筋表面的浓度超过某一阀值（临界氯离子浓度）钢筋开始锈蚀（存在水分和氧气）。为了预测混凝土中氯含量在时间和空间上以及界定钢筋对氯攻击的腐蚀抵抗的氯阀值在概念上的变化，大多数腐蚀起始模型都是以一个Fickian扩散过程的假设为基础。因此，这种基于腐蚀起始模型的控制参数是表面氯浓度(Cs)、保护层厚度(X)、在混凝土中的氯离子扩散系数(D)、氯阀值水准(Cth)和暴露年龄(ttref)。表面氯浓度取决于在环境中暴露的严重程度，而混凝土保护层厚度的变化取决于质量控制、工艺以及结构的位置和尺寸。混凝土中氯离子扩散系数主要取决于混凝土的水灰比且随年龄(t)、温度(t)和相对湿度(h)而变化，因此需要按照一个地区的水合作用和持续的老化条件计量数据修改(采用修正)。文献调查显示氯化门槛值有很大不同，是一个概率函数而不是固定或不变的。当氯浓度在0.17%至2.5%(表示为水泥质量的总氯)时，腐蚀被观测到开始。根据输入的模型参数，这样一个巨大的变化导致使用寿命估计的不同。这种变化或不确定性影响选择和项目调度问题的保养、维修、和康复的有效性。确定方法使用参数平均值，并提供一个50%的初锈概率，但概率方法为选定的腐蚀风险提供开始腐蚀的预算时间，并提出了腐蚀的概率参数灵敏度。对于评估在模型输出上的不确定性的输入参数不确定性影响，灵敏度分析是必要的。通过识别最相关参数，影响腐蚀起始时间可以在设计阶段、在施工期间(通过质量管理)、在服务中(通过调度检查和维修)采取措施，以降低腐蚀起始时间(ti)的不确定性。因此，对于以选定风险的腐蚀，一个用来有效的时间计算的完整评价方法是必要的。腐蚀起始时间对业主、设计师或者对及时作出维修优先权、维修策略、腐蚀防护、出售、购买或拆除的组织是有用的。为了优化维护计划和预算，在最佳时间，有计划的维修是最安全、最具性价比的方法。当结构需要维护和修理时该方法需要新的信息，因此要求预报腐蚀起始时间。针对高氯环境中的混凝土构件的腐蚀起始时间，本文运用简化概率分析和部分饱和混凝土的钢筋锈蚀灵敏度参数在印度海岸五个地方调查了温度和相对湿度(据地理位置)的对比效应。先前提出的以基于菲克第二扩散定律的氯离子进入模型为基础和由于持续的表面浓度条件进行确定性腐蚀起始时间分析的扩散处于使用中。当钢筋表面的氯浓度超过某一阀值（Cth）即临界氯离子浓度时，假定腐蚀开始。作为扩散系数的修正因子平均值和标准差是通过研究温度(T)和相对湿度（h）的变化确定的。其它参数如参考扩散系数(Dref)、扩散衰变常数(m)、临界氯离子含量（Cth）、表面氯浓度(Cs)、混凝土保护层(X)是从文献中估计得到的。简化概率分析包括通过评价在腐蚀起始时间内的变化确定模型的每个不确定输入参数的偏导数，这些变化是由模型的每个不确定输入参数的变化引起的。偏导数用来计算每个参数，然后模型输出即腐蚀起始时间的差异。概率密度函数和累积概率分布呈曲线型。从累积分布中能估算选定的腐蚀风险的第一腐蚀预期时间。从灵敏度分析，对影响腐蚀时间的最相关参数进行了排名。附件2：外文原文International Journal of Reliability, Quality and Safety EngineeringVol. 15, No. 6 (2008) 539553World Scientific Publishing CompanyCORROSION INITIATION TIME FOR REINFORCED CONCRETE MEMBERS ALONG INDIAN COASTS: EFFECTS OF TEMPERATURE AND RELATIVE HUMIDITY A PROBABILISTIC APPROACHSATISH.B.ALLAMPALLEWAR and A.SRIVIDYACorrosion initiation time of steel reinforcement for partially saturated concrete members subjected to chloride ingress is investigated at five places along Indian coasts using simplified probabilistic analysis and sensitivity of the parameters to reinforcement corrosion is studied. Previously proposed diffusion based chloride ingress model for constant surface chloride concentration and variable diffusion coefficient is used. Corrosion is initiated when the chloride concentration on steel reinforcement exceeds a threshold value. The various input parameters considered in the model are surface chloride concentration (Cs), chloride threshold value (Cth), Concrete cover (X), reference diffusion coefficient (Dref ), age (t), reference age (tref ), diffusion decay index (m) and monthly temperature and relative humidity correction factors f(T) and f(h) respectively; to reference diffusion coefficient. For prediction of corrosion initiation time temperature and relative humidity data collected by India metrological Department is used and all other parameters are assumed same. A large variation in corrosion initiation time is found and therefore it becomes necessary to consider the temperature and relative humidity data in a region. Life-365 considers fully saturated condition of concrete and thus underestimates the corrosion initiation time of a reinforced concrete member. The deterministic approach uses mean values of the parameters and provides a 50% probability of corrosion initiation but the probabilistic approach provides expected time of first corrosion for chosen risk of corrosion and also gives sensitivity of parameters to probability of corrosion. Corrosion initiation time in ascending order is found at Colaba, Kanyakumari, Santacruz, Chennai and Vishakhapatnam. Corrosion initiation time is useful for owner, designer, or to an organization to take decision in time of priority of repairs, repair strategy, corrosion protection in order to optimize maintenance planning and budgeting. Planned maintenance at the optimum time is the safest and most cost effective approach.Keywords: Corrosion; partially saturated concrete; chloride ingress; diffusion; temperature; relative humidity; probabilistic; sensitivity.1. IntroductionReinforced concrete structures are most widely used across the world. Reinforced concrete (RC) structures deteriorate with time in a corrosive environment affecting aesthetic, functional and structural aspects in service. The rate of deterioration depends on factors such as planning, design, construction, operation/use, and maintenance. Degradation of concrete is related to its durability aspect and to its corrosion of reinforcing steel. The corrosion of the steel reinforcement leads to concrete fracture through cracking, delamination and spalling of concrete cover, reduction of concrete and reinforcement cross sections, loss of bond between the steel reinforcement and concrete, and reduction in strength and ductility, which leads to irrecoverable losses and collapse of structures. Hence, the safety and serviceability of concrete structures in service needs to be considered. Carbonation, sulfate and chloride attack, and steel corrosion may cause the degradation of reinforced concrete members/buildings. The chloride-induced (penetration of chloride ions in to concrete) corrosion of the steel reinforcement is identified as one of the main cause of deterioration of different concrete structures (e.g. bridges, off-shore structures and parking garages). The sources of chlorides are the seawater, deicing salts, and air in marine environment. Reinforcement corrosion starts (in presence of moisture and oxygen) once the concentration of chloride ions at the reinforcing steel surface exceeds a threshold value (critical chloride content). Most corrosion initiation models are based on assumption of a Fickian process of diffusion for predicating the time and space variations of chloride content in concrete and on the concept of chloride threshold to define corrosion resistance of reinforcing steel to chloride attack. Therefore, the governing parameters of this diffusion based corrosion initiation model are the surface chloride concentration (Cs), cover depth (X), chloride diffusion coefficient in concrete (D), chloride threshold level (Cth) and exposure age (t tref ). Surface chloride concentration depends on the severity of the environmental exposure, whereas variability of concrete cover depth depends on quality control, workmanship and location and size of structure. Chloride diffusion coefficient in concrete mainly depends on water-cement ratio of concrete and varies with age (t), temperature (T ) and relative humidity (h) and hence requires to be modified (by applying correction) according to the exposure conditions for continued hydration and metrological data in a region. Literature survey has shown the value of chloride threshold can vary widely and is a probabilistic function rather than being fixed or constant. Corrosion has been observed (Glass and Buenfeld,8) to initiate at chloride concentrations from 0.17 to 2.5% chloride (expressed as total chloride by mass of cement). Such a wide variation causes service life estimates to differ, depending upon input parameters of model. This variation or uncertainty affects the validity of the choice and project scheduling of maintenance, repair, and rehabilitation alternatives. The deterministic approach uses mean values of the parameters and provide a 50% probability of corrosion initiation but the probabilistic approach provides expected time of first corrosion for chosen risk of corrosion and also gives sensitivity of parameters to probability of corrosion. Sensitivity analysis is necessary to assess the impact of uncertainties from the input parameters on the uncertainty of the model output. By identifying the most relevant parameters affecting the corrosion initiation time measures can be taken at design stage, during construction (by quality control), and in service (by scheduling inspection and maintenance) to reduce the uncertainty in corrosion initiation time (ti). Hence, a complete evaluation method for effective calculation of time to corrosion for chosen risk is necessary. Corrosion initiation time is useful for owner, designer, or to an organization to take decision in time of priority of repairs, repair strategy, corrosion protection, sell, purchase, or demolish. In order to optimize maintenance planning and budgeting, planned maintenance at the optimum time is the safest and most cost effective approach. The approach needs up to date information when the structure will need maintenance and repair and hence it is required to predict Corrosion initiation time. The present paper examines the comparative effect of temperature and relative humidity (according to the geographic location) at five places along Indian coasts on corrosion initiation time for reinforced concrete members in chloride laden environments using simplified probabilistic analysis and sensitivity of the parameters to reinforcement corrosion for partially saturated concrete. A previously proposed diffusion based chloride ingress model (Srividya and Allampallewar,4) based on Ficks second law of diffusion and for constant surface chloride concentration condition to perform deterministic analysis for corrosion initiation time is used. Corrosion initiation is assumed when the chloride concentration on steel reinforcement exceeds a threshold value (Cth) i.e. critical chloride co