Assessment of Existing Reinforced Concrete Structures

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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.