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 - m录影带灾难和多伦多丙烷爆炸等事件也凸显了加拿大已建成的基础设施在意外爆炸和工业爆炸面前的脆弱性。桥梁也容易受到爆炸的威胁，并且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，桥梁的关键结构部件是直接加载的，因此可能在低距处暴露在大爆炸荷载下。直到最近，防爆设计在加拿大的建筑和桥梁设计中还不常见；因此，需要对大量现有建筑物和桥梁进行改造，以提高抗爆能力，确保加拿大人的安全。以前的爆炸事件，如俄克拉荷马城爆炸案，已经提高了人们对改造柱子的必要性的认识，以提高混凝土建筑和桥梁的生存能力。砖石墙是在加拿大许多老建筑中发现的另一种脆弱的结构类型，无论是填充墙还是结构墙。现代规范要求砌体建筑中使用最少的钢材，但旧建筑没有这样的要求；因此，现有建筑中的无加固砌体墙在极低的面外爆炸荷载下容易倒塌。这样的墙可能会急剧倒塌，高速弹丸可能会伤害建筑物的居住者。超高性能混凝土（UHPC）是一类新型的先进水泥基复合材料，具有显著的强度、抗拉性、韧性和损伤容限。这些独特的特性使UHPC成为防爆设计应用的理想材料。这种材料的高粘合能力，再加上它的铸造能力非常薄但坚固的层，也使它成为改造脆弱结构以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关键基础设施开发使用先进水泥基复合材料的新型爆破改造策略。长期目标包括开发改造方法、分析工具和设计程序，以捕获改造元件的动态响应。短期目标是开发新的uhpc改造，以保护混凝土和砌体结构中的结构和非结构元素。该范围将包括四项主要任务；1)材料研究，以研究UHPC改造的高应变行为和粘结响应；2)UHPC护套在混凝土建筑/桥梁柱中的应用；3)UHPC覆盖层在砌体墙中的应用；iv)开发用于预测uhpc改造的爆炸响应的分析模型。预计该研究计划将导致CSA标准的最佳实践指南和规定的发展，以造福加拿大建筑业。

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.