【作者】 郭冬梅；

【导师】 项贻强；

【作者基本信息】 浙江大学 ， 桥梁与隧道工程， 2014， 博士

【摘要】 沿海地区的公路桥梁由于受到氯离子的侵蚀等环境因素使得钢筋锈蚀,进而结构性能劣化、抗力衰减,甚至是倒塌破坏,不得不花费大量资金维修加固甚至是重建,造成巨大的经济损失和严重的社会影响。本文在国家自然基金“在役混凝土箱梁桥时变承载力的分析理论及试验研究”的资助下,结合“台州沿海混凝土桥梁性能退化及灾变机理研究”项目,基于全寿命周期理论,对沿海在役混凝土桥梁的性能劣化机理从耐久性、可靠性展开研究与讨论,预测既有混凝土桥梁的耐久性寿命、承载力寿命,进而确定结构的剩余使用寿命以及桥梁的最佳维护策略等。主要研究工作如下：1、从耐久性、可靠性以及全寿命周期理念三个方面综述和概括了混凝土结构预测剩余使用寿命的研究进展及预测模型,指出研究现状及存在的不足；统计分析了台州地区340座混凝土桥梁病害发生的部位,重点研究下部结构构件的耐久性和可靠性,从而评估结构的安全性；2、针对台州沿海混凝土桥梁经受氯离子侵蚀、混凝土碳化以及钢筋锈蚀的劣化特点,在碳化深度的计算模型中引入了水灰比参数,并进行了构件层次上的混凝土碳化和钢筋的锈胀的动态可靠度的分析计算,预测了工程实例的耐久性寿命,为桥梁管养部门提供可靠的依据；3、提出了基于荷载影响因子和氯离子结合能力的两种因素耦合的氯离子扩散的修正模型,与传统的考虑单一因素的氯离子扩散模型相比,修正的氯离子扩散模型更贴近混凝土桥梁的实际,更加合理；基于此氯离子扩散的修正模型,建立了考虑荷载影响因子和氯离子结合能力的两种因素的钢筋锈蚀模型,并与现有的钢筋锈蚀模型进行了对比,所提出的考虑荷载影响因子和氯离子结合能力的两种因素的钢筋锈蚀模型更加合理,为准确的预测混凝土桥梁的剩余寿命提供理论依据；4、基于上述氯离子扩散修正模型和钢筋锈蚀模型(材料劣化模型),只考虑钢筋材料对结构抗力衰减的影响,计算分析了背景桥梁各构件的时变可靠度与失效概率,进一步预测了剩余使用寿命；5、基于系统部件可靠性评估的寿命分布函数,应用于桥梁工程,对结构的各个构件的连接形式(串联、并联以及混联)进行了失效概率的计算分析,给出了寻求基于寿命周期函数的最佳维护策略的步骤,从失效概率和累积成本找出最优的维修加固方案,结合工程实例进行了验证为桥梁管养部门提供理论指导；6、沿海地区公路桥梁性能的劣化表征为可靠性指标和状态指标的劣化,建立了可靠性指标和状态指标的劣化模型,性能劣化模型中考虑了荷载和环境的影响,并以性能指标劣化模型为基准,建立了全寿命周期内的维护策略的优化模型,利用遗传算法(GA)对优化模型进行了分析计算,综合评价了全寿命周期内的经济效益,给出了数值实例的最优维护策略。更多还原

【Abstract】 Steel bars of coastal highway bridge are easy to be corroded due to chloride ion erosion and many other environmental factors, which will lead to the degradation of structure performance and even structural collapse. Because of those problems, a lot of money needs to be paid to repair, reinforce or to rebuild the bridges, which will cause large economic losses and bad social impact.This paper is supported by National Science Foundation of "Analysis theory and test study on time-variant bearing capacity of in-service concrete box-girder bridge", and the project of "Taizhou coastal concrete bridge degradation and disaster mechanism research".In order to predict the durability life, carrying capacity and remaining service life of the existing concrete bridges, and to suggest the best bridge maintenance strategies, the research on degradation mechanism of coastal concrete bridge service performance was conducted by using Life-cycle Theory. Specific studies are as follows:1. The models for predicting the remaining service life of concrete structures were summarized, and their study scope and deficiencies were pointed out from the aspects of durability, reliability and life-cycle concept. Disease positions of340concrete bridges in Taizhou were statistical analyzed. For the purpose of assessing the safety of bridges, the durability and reliability of substructures were mainly focused on.2. Considering the characteristics of concrete carbonation, chloride diffusion and steel corrosion of coastal concrete bridges in Taizhou, the parameter of water-cement ratio was introduced into the calculation model for carbonation depth. The dynamic reliability of concrete carbonation and steel rust expansion was calculated and discussed from the component level. Finally, the durability life of an existing bridge was predicted using the modified model.3. A modified chloride diffusion model was proposed by considering two factors of load impact and chloride iron combining capacity. Compared to traditional chloride iron diffusion model, the modified model could be more reasonable and close to the reality of existing concrete bridges. Also, based on the factors of load impact and chloride iron combining capacity, a corrosion model of steel bar was further put forward, which could provide theoretical basis for predicting the remaining life of concrete bridges4. Time-varying reliability and failure probability of the background project were calculated by using the above chloride iron diffusion model and reinforcement corrosion model, in which only the effect of reinforcement corrosion on the structural resistance was considered. The remaining useful life was also predicted.5. Based on the life distribution function in reliability assessment of system components, the system security and maintenance strategies of coastal highway bridges were analyzed. The beast maintenance strategy steps were given by the life-cycle function, which was also verified by practical engineering.6. The deterioration of highway bridges in coastal areas is characterized by the degradation of reliability index and state index. A deteriorated model of reliability index and state index was established. The effect of loads and environment was considered in the proposed model. At the same time, a life-cycle maintenance strategy optimization model was also developed, and the genetic algorithm (GA) was used as solution method. Finally, the life-cycle economic benefits and optimal maintenance strategy of a practical bridge were evaluated as an example.更多还原