Assessment of Existing Reinforced Concrete Structures

影响加拿大钢筋混凝土（RC）公路基础设施的主要降解机制是钢筋的氯化物腐蚀。这种破坏往往与加拿大冬季特有的冻结/融化循环的作用相结合。加拿大现有的钢筋混凝土结构设计标准主要关注结构性能，没有明确尝试评估长期劣化机制的影响。虽然加拿大混凝土设计标准中提到了耐久性极限状态，但它仅仅是对混凝土配合比设计、最小混凝土覆盖厚度以及施工现场混凝土浇筑和养护质量控制的规范性规范。实际上，不仅在规范中，而且在结构工程专业中，对承载能力和耐久性的处理已经分开。为了确保RC基础设施的安全使用性能和最小化故障风险，必须开发测试和分析/数值工具来评估这种恶化对RC基础设施的可使用性和最终容量的影响。本研究的主要目的是评估钢筋腐蚀和霜冻损伤对钢筋混凝土基础设施的使用能力和强度的影响。这个问题的三个方面将被研究：(i)使用混凝土电阻率测量作为耐久性的质量控制和预测指标，（ii）劣化机制对RC结构构件结构性能的影响，以及（iii）地震荷载对劣化RC桥梁的影响。这将通过实验测试和使用有限元方法的数值模拟来完成。实验方案的目的是结合现有的钢筋腐蚀和霜冻损伤检测和评估试验，开发使用电阻率的测试方法。该研究的数值部分旨在将材料劣化模型与当前的结构分析方法相结合，以模拟RC基础设施在使用和极限条件下的行为。本研究的意义在于提高了对退化对RC结构的可用性和剩余强度的影响的理解，并通过实施现有受影响结构的评估指南，将这些知识直接应用于加拿大老化和退化基础设施的有效管理。

The main degradation mechanism that affects reinforced concrete (RC) highway infrastructure in Canada is chloride-induced corrosion of reinforcing steel. This damage is often compounded by the action of freezing/thawing cycles characteristic of a Canadian winter. Existing Canadian standards for design of RC structures focus mainly on the structural performance, without an explicit attempt to evaluate the effect of deterioration mechanisms over long periods of time. Although a durability limit state is mentioned in the Canadian concrete design standard, it is merely a prescriptive specification on concrete mix design, minimum concrete cover thickness, and quality control in the placement and curing of concrete at the job site. In effect, the treatment of load carrying capacity and durability has been separated, not only in the codes but also in the profession of structural engineering. To assure the safe in-service performance and minimise the risk of failure of RC infrastructure, it is imperative that testing and analytical/numerical tools are developed to assess the consequences of this deterioration on the serviceability and ultimate capacity of RC infrastructure. The primary goal of this research is to assess the impact of reinforcement corrosion and frost damage on the serviceability and strength of RC infrastructure. Three aspects of this problem are to be investigated: (i) the use of concrete electrical resistivity measurements as a quality control and predictor of durability, (ii) the impact of deterioration mechanisms on the structural behaviour of RC structural members, and (iii) the impact of earthquake load on deteriorated RC bridges. This is intended to be done through both experimental tests and numerical simulations using the finite element method. The experimental program has as its aim to develop testing methodologies of the use of electrical resistivity in combination with existing tests for reinforcement corrosion and frost damage detection and evaluation. The numerical component of the research aims at integrating material deterioration models with current methods of structural analysis in order to simulate the behaviour of RC infrastructure under both in-service and ultimate conditions. The significance of this research is the improved understanding of the effects of deterioration on serviceability and residual strength of RC structures, and the direct application of this knowledge to the effective management of Canada's aging and deteriorating infrastructure through the implementation of assessment guidelines of existing affected structures.