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

大部分基础设施，特别是桥面，暴露在恶劣的环境条件下，出现早期老化。因此，建筑中使用的一些材料和设计标准不允许在没有干预的情况下达到结构的预期寿命（超过75年）。有希望显著延长基础设施耐久性的方法是修改标准强度混凝土（NSC）的使用条件设计标准和促进纤维增强混凝土（FRC）的使用。与NSC相比，FRC在机械性能和耐久性方面有显著改善。然而，在服务中缺乏适应的设计标准阻碍了这些材料在加拿大的充分利用。*******研究计划的总体目标是评估开裂的NSC和FRC结构构件的力学行为和耐久性，以建立有效的设计标准。具体目标是：(a)评估桥梁代表性条件下钢筋混凝土的透水性；(b)再现这些条件下钢筋混凝土的输水和力学行为；(c)提出适用于各种混凝土类别的允许裂缝宽度和钢筋应力水平，以确保结构的耐久性。*******科学方法的新颖之处在于在最具代表性的桥梁条件下评估混凝土的透水性，这意味着钢筋混凝土承受永久荷载和随机开裂。将使用和改进最近研制的一种独特的实验装置；它可以准确地评估透水性，裂缝宽度和钢筋混凝土组件的应力，同时应用静态，恒定或循环载荷。*******主要涉及14 HQP的研究计划将包括实验研究，以评估FRC成分，设计条件，加载条件和环境条件对透水性的影响。基于所获得的力学和渗透性结果，还将进行非线性有限元分析，以再现服役中钢筋混凝土结构的裂缝形态和水侵，并提出服役条件下NSC和FRC的允许裂缝宽度和钢筋应力水平。*******在许多情况下，目前的钢筋混凝土结构设计标准不允许达到其预期寿命。本研究项目的实验和数值研究将为NSC和FRC提供有效的允许裂缝宽度和钢筋应力水平，以确保结构的长期耐久性。这些现行的设计准则将被建议纳入建筑规范。它们的使用将提高基础设施的耐久性，从而降低其维护和维修成本。******

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.******