Behaviour and design of concrete structures for sustainability and resilience

钢筋混凝土在现代基础设施的发展中发挥了关键作用。 不幸的是，在混凝土结构中观察到的大多数与耐久性相关的问题都来自钢筋的腐蚀，即使混凝土仍然健康，钢筋的腐蚀也会使结构存在缺陷。本提案中提出的另一个问题是碱-硅反应，它会削弱混凝土和结构。因此，大多数国家的混凝土基础设施处于可怕的状态。在加拿大，冻融循环和在桥梁上使用除冰盐进一步加剧了这一问题。加拿大许多城市的居民经常观察到这种现象，即从桥梁上掉落的混凝土碎片。 纤维增强聚合物（FRP）是钢筋加固的一种经济替代品，可用作外部加固以升级现有结构或新结构的内部加固。近年来，人们研究了在混凝土板、梁和其他受弯构件中使用FRP作为内部钢筋的情况，并制定了设计指南，这些指南现在可用于设计规范，如《纤维增强聚合物建筑结构的设计和施工》和《加拿大公路桥梁规范》。虽然在许多这些领域还需要进一步的工作，而且正在进行中，但使用FRP筋抵抗压缩荷载需要立即引起注意。目前的规范不允许使用FRP筋抵抗结构中的压缩荷载，主要是由于缺乏实验和分析证据。使用FRP筋的另一个挑战是弯曲筋的性能，弯曲筋的强度会因弯曲而显著降低。规范委员会认为这些问题是最迫切的研究需求。 拟议的工作将侧重于在结构中使用FRP的挑战，其中一些在上面讨论。该方法包括开发材料行为和结构行为的分析模型。这些模型将得到多伦多大学最先进的实验室进行的大量实验数据的支持和证实。将在实际荷载（包括重复和模拟地震力）下对大型和小型样本进行测试，并将包括大型柱和梁柱接头。用普通和活性ASR混凝土制成的小试样将用于开发本构模型，并将研究限制和冻融等影响。这项工作将借鉴PI多年来在钢筋混凝土构件上开展的工作。 最终目标是制定可纳入各种规范的设计准则。这项工作还将帮助结构设计人员获得信心，使用这些新材料来改造、设计和建造更耐用和可持续的基础设施，从而产生显著的经济效益。

Steel-reinforced concrete has played a critical role in the development of modern infrastructure. Unfortunately, most of the durability-related problems observed in concrete structures flow from corrosion of steel reinforcement that makes structures deficient even when the concrete is still healthy. Another issue addressed in this proposal is the alkali-silica reaction that weakens the concrete and the structure. As a result, the concrete infrastructure in most countries is in a dire state. In Canada, the problem is further exacerbated by freeze-thaw cycles and the use of de-icing salts on bridges. Residents of many cities in Canada routinely observe this phenomenon in the form of falling concrete pieces from bridges. An economical alternative to steel reinforcement is fibre reinforced polymers (FRP) that can be used as external reinforcement to upgrade existing structures or internal reinforcement for new ones. Use of FRP as internal reinforcement in concrete slabs, beams and other flexural members has been investigated in recent years and design guidelines developed that are now available in design codes such as “Design and construction of building structures with fibre-reinforced polymers” and Canadian Highway Bridge Code. Although further work is needed and underway in many of these areas, it is the use of FRP bars to resist compressive loads that needs immediate attention. Current codes do not allow the use of FRP bars to resist compression loads in structures primarily due to a lack of experimental and analytical evidence. Another challenge in the use of FRP bars is the behaviour of bent bars, which show significant reduction in strength as a result of curvature. Code committees consider these issues as the most urgent research needs. The proposed work will focus on the challenges in the use of FRP in structures some of which are discussed above. The methodology includes development of analytical models for material behaviour and structural behavior. These models will be supported by, and corroborated with data from a large variety of experiments that will be conducted in state-of-the-art laboratories at the University of Toronto. Large and small specimens will be tested under realistic loads including repeated and simulated seismic forces, and will include large scale columns and beam-column joints. The small specimens made with normal and reactive ASR concrete will be used to develop constitutive models and will investigate such effects as confinement and freeze-thaw. This work will draw significantly from the work on steel-reinforced concrete members carried out by the PI over the years. The ultimate goal is to develop design guidelines that can be included in various codes. This work would also help structural designers gain confidence in using these new materials to retrofit, design and construct more durable and sustainable infrastructure producing significant economic benefits.