Ultra-high-performance concrete (UHPC) retrofits for increased blast protection of concrete and masonry structures

最近在世界各地发生的炸弹袭击表明，现有建筑在爆炸荷载下是脆弱的。Lac-Mégantic灾难和多伦多丙烷爆炸等事件也突显了加拿大已建基础设施在意外和工业爆炸面前的脆弱性。桥梁也容易受到爆炸威胁，并由于其开放的通道而构成独特的设计挑战。此外，与建筑物不同的是，桥梁中的关键结构部件是直接加载的，因此可能在低距离处暴露在大爆炸荷载下。直到最近，抗爆设计在加拿大的建筑和桥梁设计中并不常见；因此，需要对大量现有建筑和桥梁进行翻新，以提高爆炸韧性并确保加拿大人的安全。之前的爆炸事件，如俄克拉荷马城爆炸事件，提高了人们对需要加装柱子以提高混凝土建筑和桥梁的生存能力的认识。砖石墙是加拿大许多老建筑中发现的另一种脆弱的结构类型，无论是作为填充墙还是结构墙。现代规范对砌体结构的钢筋要求最低，但较老的建筑没有这样的要求；因此，现有建筑中的无筋砌块(URM)墙在极低的面外爆炸荷载下容易倒塌。这样的墙可能会戏剧性地坍塌，高速投射可能会伤害建筑物的居住者。超高性能混凝土(UHPC)是一种新型的高性能水泥基复合材料，具有优异的强度、抗拉强度、韧性和损伤容限。这些独特的特性使超高性能混凝土成为防爆设计应用的理想材料。这种材料的高粘结能力，加上它能够浇铸成非常薄但坚固的层，也使它成为加固脆弱结构抵御爆炸的理想材料。拟议研究计划的长期目标是为加拿大的关键基础设施开发使用先进水泥基复合材料的新型鼓风改造策略。长期目标包括开发改造方法、分析工具和设计程序，以捕捉改造后的要素的动态反应。短期目标是开发新型超高性能混凝土，用于保护混凝土和砖石结构中的结构和非结构构件。该范围将包括四项主要任务：i)材料研究，以调查超高混凝土加固的高应变行为和粘结反应，ii)超高性能混凝土护套在混凝土建筑/桥梁柱中的应用，iii)超高性能混凝土覆盖层在砖墙中的应用；iv)开发用于预测超高性能混凝土加固的爆炸反应的分析模型。据设想，该研究计划将为加拿大建筑业制定CSA标准的最佳实践指南和规定。

Recent bomb attacks around the world have demonstrated the vulnerability of existing buildings to blast loads. Events such as the Lac-Mégantic disaster and Toronto Propane Explosion also highlight the vulnerability of Canada's built infrastructure to accidental and industrial explosions. Bridges are also vulnerable to blast threats, and pose unique design challenges due to their open access. In addition, unlike buildings, key structural components in bridges are directly loaded and therefore may be exposed to large blast loads at low standoff. Until recently, blast-resistant design was not common in the design of buildings and bridges in Canada; thus, a large inventory of existing buildings and bridges are in need of retrofits to increase blast resilience and ensure safety and security of Canadians. Previous blast incidents such as the Oklahoma City Bombing have raised awareness of the need for retrofitting columns to increase the survivability of concrete buildings and bridges. Masonry walls are another vulnerable structural type found in many older buildings in Canada, either as infill or structural walls. Modern codes require minimum steel in masonry construction, but older buildings had no such requirement; thus unreinforced masonry (URM) walls in existing buildings are vulnerable to collapse under very low out-of-plane blast loads. Such walls can fail dramatically, with high speed projectiles that can injure building occupants. Ultra High Performance Concrete (UHPC) is a new class of advanced cement-based composite with remarkable strength, tensile resistance, toughness and damage tolerance. These unique features make UHPC an ideal material for blast-resistant design applications. This material's high bond capacity, coupled with its ability to be cast in very thin yet strong layers also make it an ideal material to retrofit vulnerable structures against blasts. The long term goal of the proposed research program is to develop novel blast retrofit strategies using advanced cement-based composite materials for critical Canadian infrastructure. The long term objectives include the development of retrofit methodologies, analytical tools and design procedures that can capture dynamic response of retrofitted elements. The short-term objective is to develop novel UHPC-retrofits for the protection of structural and non-structural elements in concrete and masonry structures. The scope will consist of four main tasks; i) materials research to investigate the high-strain behavior and bond response of the UHPC retrofits, ii) application of UHPC-jacketing in concrete building/bridge columns, iii) application of UHPC-overlays to masonry walls; iv) development of analytical models for predicting the blast response of the UHPC-retrofits. It is envisioned that the research program will result in the development of best practice guidelines and provisions for CSA Standards for the benefit of the Canadian construction industry.