Concrete crack width under combined reinforcement corrosion and applied load

摘要

For reinforced concrete structures subjected to chlorides, carbon dioxide laden and other aggressive environments, corrosion of the reinforcing steel is seen as a global problem. Maintenance and repairs resulting primarily from premature concrete cracking and spalling have an estimated cost running to $100 billion per annum world-wide. The continual demands for greater load carrying capacity of existing infrastructure only exacerbate the problem. In practice, concrete crack width propagation is seen as one of the most important criteria for design and assessment of the long term serviceability of concrete structures. It is therefore economically beneficial to have a fundamental understanding of the growth of the crack width over time so that better informed decisions can be made regarding the carrying out of any repairs. This research attempts to examine the process of concrete cracking and determine the surface crack width of concrete structures under the combined effects of reinforcement corrosion and applied load in both an analytical and numerical manner. In the analytical method, a model for stiffness reduction of cracked concrete has been derived based on the concept of fracture energy and an analytical solution has been obtained. In the numerical method, an interfacial element has been developed to predict concrete crack width under combined effects based on a cohesive crack model in conjunction with finite element codes. To help accurate prediction of crack width in the numerical method, a realistic constitutive relationship for concrete under direct tension has been obtained from the laboratory experiments. It is concluded in this thesis that both the analytical and numerical methods are one of very few available theoretical methods that can predict with reasonable accuracy concrete crack width of reinforced concrete structures under the combined effects of reinforcement corrosion and applied load. This research focuses on concrete cracking caused by reinforcement corrosion and applied load without considering other factors, e.g., weathering, freeze-thaw and chemical attack. Both methods can be used as a tool to assess the serviceability of corrosion affected concrete infrastructure if reinforcement corrosion and applied load are the main causal factors of concrete cracking. For this type of concrete structures, therefore, scientific information can be provided for asset managers in decision making regarding possible interventions. Timely interventions have the potential to prolong the service life of reinforced concrete structures.