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

最近世界各地的炸弹袭击表明，现有建筑物在爆炸载荷下很脆弱。Lac-Mégantic灾难和多伦多丙烷爆炸等事件也突出表明，加拿大的建筑基础设施容易受到意外和工业爆炸的影响。桥梁也容易受到爆炸威胁，并由于其开放式通道而带来独特的设计挑战。此外，与建筑物不同，桥梁中的关键结构部件直接加载，因此可能在低间隔时暴露于大的爆炸载荷。直到最近，抗爆设计在加拿大的建筑物和桥梁设计中并不常见;因此，大量现有建筑物和桥梁需要改造，以提高抗爆能力，确保加拿大人的安全和安保。 以前的爆炸事件，如俄克拉荷马州城市爆炸事件，提高了人们对改造柱子以提高混凝土建筑物和桥梁生存能力的认识。砌体墙是加拿大许多旧建筑中发现的另一种脆弱的结构类型，无论是填充墙还是结构墙。现代规范要求砌体结构中的钢筋最少，但旧建筑物没有这样的要求;因此，现有建筑物中的无钢筋砌体（URM）墙在非常低的平面外爆炸荷载下容易倒塌。这样的墙可能会急剧下降，高速射弹可能会伤害建筑物的居住者。超高性能混凝土（UHPC）是一种新型的先进水泥基复合材料，具有优异的强度、抗拉性能、韧性和损伤容限。这些独特的特性使UHPC成为抗爆设计应用的理想材料。这种材料的高粘结能力，加上其能够浇铸成非常薄但坚固的层，也使其成为改造脆弱结构以抵御爆炸的理想材料。拟议的研究计划的长期目标是开发新的爆破改造战略，使用先进的水泥基复合材料的关键加拿大基础设施。长期目标包括改进方法、分析工具和设计程序的发展，这些方法、工具和设计程序能够捕捉到改进元件的动态响应。短期目标是开发新的UHPC改造，用于保护混凝土和砌体结构中的结构和非结构元件。范围将包括四项主要任务：i）材料研究，以调查UHPC改造的高应变行为和粘结反应; ii）UHPC护套在混凝土建筑/桥梁柱中的应用; iii）UHPC覆盖层在砌体墙中的应用; iv）开发分析模型，以预测UHPC改造的爆炸反应。据设想，该研究计划将导致最佳实践准则和CSA标准的规定，为加拿大建筑业的利益的发展。

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.