Development of innovative strategies for durable bridge design and rehabilitation by use of high and ultra-high performance fibre reinforced concretes

大部分混凝土桥梁暴露在恶劣的环境条件下，表现出严重的退化。在桥墩、梁和桥面上观察到的主要现象是钢筋腐蚀和混凝土剥落，这导致了承载能力的降低和基础设施耐久性的改变。自20世纪90年代以来，大量的研究集中在高性能和超高性能纤维增强混凝土（HPFRC和UHPFRC）的发展上。与普通强度混凝土相比，HPFRC和UHPFRC在机械性能和耐久性方面有显著改善。因此，这些材料在桥梁基础设施的设计和修复中的应用潜力是显而易见的。必须进行研究以完成HPFRC和UHPFRC的特性，从而促进其在基础设施中的利用。提出的研究计划分为两个主题。Topic(1)旨在介绍HPFRC和UHPFRC的透水性和自愈性的基础知识。材料参数（纤维含量，粘合剂的类型和体积）和结构参数（静态和循环载荷）的影响将被研究。主题(2)的目的是评估结构中纤维取向对高荷载下FRC尺寸效应和蠕变的影响。从而估算不同条件下HPFRC和UHPFRC的硬化和软化行为的开始和程度，以及开裂对粘弹性的贡献。研究课题将结合实验测试和非线性有限元分析。拟议的研究将导致HPFRC和UHPFRC在可用性方面的应变和强度能力的优化利用，并制定确保基础设施的最佳机械性能和耐久性的详细规定。该研究项目将促进设计和修复新策略的发展，降低维护成本，提高桥梁的长期性能。其中技术人员1人，博士生1人，硕士生4人，本科生7人。HQP将有很多机会在这个研究项目中加深知识和获得新技能。

A large proportion of concrete bridges exposed to severe environmental conditions present significant deterioration. The main phenomena observed on piers, beams and bridge decks are reinforcement corrosion and concrete spalling, which have for consequences the reduction of the load-carrying capacity and the alteration of the durability of infrastructure. Since the 1990's, considerable research has been focused on the development of High and Ultra-High Performance Fibre Reinforced Concretes (HPFRC and UHPFRC). Compared to normal strength concrete, HPFRC and UHPFRC present outstanding improvements in terms of mechanical properties and durability. Therefore, the potential of application of those materials for design and rehabilitation of bridge infrastructure is obvious. Research must be performed to complete the characterisation of HPFRC and UHPFRC, and thus promote their utilisation in infrastructure. The proposed research program is divided in two topics. Topic (1) aims to bring fundamental knowledge on water permeability and self-healing of HPFRC and UHPFRC. The influence of material parameters (fibre content, type and volume of binder) and structural parameters (static and cyclic loadings) will be studied. Topic (2) has for objectives to evaluate the impact of fibre orientation in structures on the FRC size effect and creep under high loads. Thus the onset and the extent of hardening and softening behaviours of HPFRC and UHPFRC will be estimated in various conditions, as well as the contribution of cracking on viscoelasticity. Research topics will combine experimental testing and nonlinear finite element analysis. The proposed research will lead to the optimized utilisation of strain and strength capacities of HPFRC and UHPFRC at serviceability, and to elaborate provisions ensuring an optimal mechanical behaviour and durability of infrastructure. The research program will promote the development of new strategies for design and rehabilitation, reduce maintenance costs and improve the long term performance of bridges. It will involve 1 technician, 1 Ph.D. and 4 M.Sc. students and 7 undergraduate students. Many occasions will be given to HQP to deepen knowledge and acquire new skills within this research program.