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

很大一部分基础设施，特别是桥面，暴露在恶劣的环境条件下，并出现早期恶化。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)。为了显著提高基础设施的耐久性，有希望的方法是修订正常强度混凝土(NSC)在服役条件下的设计标准，并促进纤维混凝土(FRC)的使用。与NSC相比，FRC在力学性能和耐久性方面有了显著的改善。然而，在使用中严重缺乏适用的设计标准，阻碍了这些材料在加拿大的充分利用。 该研究计划的总体目标是评估开裂的NSC和FRC结构组件的力学性能和耐久性，以建立在服役条件下的有效设计标准。具体目标是：(A)评估桥梁典型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水分运移和力学行为，(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。 这种科学方法的创新之处在于，在最具代表性的桥梁条件下，即钢筋混凝土承受永久荷载和随机裂缝的情况下，评估混凝土的透水性。最近开发的一种独特的实验装置将被使用和改进；它可以在施加静态、恒定或循环荷载的同时，准确地评估钢筋混凝土构件的透水性、裂缝宽度和钢筋应力。 主要涉及14个HQP的研究计划将包括试验研究，以评估FRC组成、设计条件、加载条件和环境条件对透水性的影响。根据得到的力学和渗透性结果，还将进行非线性有限元分析，以再现在役钢筋混凝土结构的裂缝形态和渗水情况，并建议在服役条件下NSC和FRC的允许裂缝宽度和钢筋应力水平。 在许多情况下，现行的钢筋混凝土结构设计标准不允许达到其预期寿命。该研究程序的试验和数值研究将提供与NSC和FRC相适应的有效允许裂缝宽度和钢筋应力水平，以确保结构的长期耐久性。这些服役中的设计标准将被建议引入施工规范。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.