Evaluation and Prediction of the Mechanical Behavior and Durability of FRC for Optimization of Design Criteria at Serviceability Limit States for Bridges

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Large proportion of infrastructures, particularly bridge decks, are exposed to severe environmental conditions and present an early deterioration. Thus, some materials and design criteria used in construction do not allow reaching the expected lifetime of structures (over 75 years) without intervention. Promising methods to extend significantly the durability of infrastructures are to revise design criteria in service conditions for normal strength concretes (NSC) and promote utilization of Fibre Reinforced Concretes (FRC). Compared to NSC, FRC presents significant improvements in terms of mechanical properties and durability. However, a crucial lack of adapted design criteria in service impedes full exploitation of these materials in Canada.*******The general objective of the research program is to evaluate the mechanical behaviour and the durability of cracked NSC and FRC structural components to establish efficient design criteria in service conditions. The specific objectives are to: (a) evaluate water permeability of reinforced concrete under representative conditions of bridges, (b) reproduce the water transport and mechanical behavior of reinforced concrete under these conditions, (c) propose admissible crack widths and rebar stress levels applicable to various concrete categories to ensure durability of structures.*******The novelty of the scientific approach is to evaluate water permeability of concrete in the most representative conditions of bridges, which means on reinforced concrete sustaining permanent loads and randomly cracked. A unique experimental device developed recently will be used and improved; it allows accurate evaluation of water permeability, crack widths and rebar stresses in a reinforced concrete component simultaneously to the application of static, constant or cyclic loadings.*******The research program involving mainly 14 HQP will include experimental studies to evaluate the impact of FRC composition, design conditions, loading conditions, and environmental conditions on water permeability. Based on mechanical and permeability results obtained, nonlinear finite element analysis will also be conducted to reproduce crack patterns and water penetration in reinforced concrete structures in service, and to propose admissible crack widths and rebar stress levels for NSC and FRC in service conditions.*******In many cases current design criteria in service for reinforced concrete structures do not allow reaching their expected lifetime. Experimental and numerical studies of this research program will provide efficient admissible crack widths and rebar stress levels adapted for NSC and FRC to ensure long-term durability of structures. These design criteria in service will be proposed for introduction in construction codes. Their utilization will improve durability of infrastructures, thus lowering their maintenance and repair costs.******