Fostering the new generation of UHPFRC infrastructures in Canada: characterizing and modeling the effect of fibre orientation on the structural ductility

虽然魁北克的大多数混凝土基础设施处于严重劣化状态，但现在至关重要的是考虑新复合材料的潜力，以便更好地设计下一代基础设施系统，包括节省材料、延长使用寿命、降低维护成本、加快施工速度和环境友好性。在所有新兴的复合材料中，超高性能混凝土(UHPC)正以其优异的性能成为土木工程领域的真正突破。超高性能钢纤维混凝土的动力是通过优化设计的纤维加固实现的结构延性。作为一个主要结果，延性意味着裂缝宽度减小和高耐久性。然而，试验发现，当纤维大部分取向在不利方向时，超高性能钢纤维混凝土结构的显著延性可能会完全丧失。目前，由于缺乏可靠的方法来解释纤维分布的影响，超高性能混凝土的工业应用受到限制。该项目旨在开发一种新的基于模型的方法，通过直接考虑纤维的机制和分布来促进超高性能混凝土桥梁的创新解决方案。所提出的研究是基于理论、实验测试和计算机模拟相结合的综合方法。主要研究目标是：(I)开发一种新的非局部损伤模型，能够根据纤维分布直接预测UHPFRC结构的延性；(Ii)提供一个强大的工程工具，可以帮助工程师分析UHPFRC结构；(Iii)提供一种基于模型的可靠性方法，将允许加拿大工业界通过掌握纤维分布的不确定性来设计安全的UHPFRC结构；(Iv)有助于升级第一个UHPFRC建议指南并推进与加拿大设计手册的协调。该项目成果的价值在于加深目前对超高性能混凝土结构中纤维分布作用的理解，以及开发必要的工具和方法以促进超高性能混凝土在加拿大下一代基础设施中的实施。

While a large majority of concrete infrastructures in Quebec undergo to an advanced state of deterioration, it is now critical to consider the potentials of new composites for better designing the next infrastructure system in terms of material saving, longer life, reduced maintenance cost, faster construction and environmental friendliness. Among all the emerging composites, Ultra High Performance Concretes (UHPC) is becoming a truly breakthrough in civil engineering thanks to their outstanding properties. The driving force of UHPFRC is the structural ductility which has been achieved by means of the optimally designed fibre reinforcement. As a major consequence, ductility infers reduced crack widths and high durability. However, it was experimentally found that the remarkable ductility of UHPFRC structures can be completely lost when the fibres are mostly oriented in an unfavourable direction. The industrial implementation of UHPFRC is today limited by the lack of a reliable method which accounts for the effect of the fibre distribution. The project aims to develop a new model-based approach to foster innovative solutions of UHPFRC bridges by directly accounting for the fibres' mechanisms and distribution. The proposed research is based on a comprehensive approach which combines theory, experimental tests and computer simulation. The major research objective are: (i) to develop a new non-local damage model which can directly predict the ductility of UHPFRC structures from the fibre distribution; (ii) to provide a powerful engineering tool which can aid engineers to analyze UHPFRC structures; (iii) to provide a model-based reliability approach which will allow Canadian industries to engineer safe UHPFRC structures by mastering the uncertainty due to fibre distribution; (iv) to contribute to upgrade the first UHPFRC recommendation guidelines and to advance the harmonization with the Canadian Design Handbook. The value of the project results is to deep the current understanding of the role of fibre distribution in UHPFRC structures as well as to develop the needed tools and method to foster the implementation of UHPFRC in the next generation of Canadian infrastructure.