Improving durability of joints of precast decks

提高预制桥面板接缝的耐久性

• 批准号: RGPIN-2014-05914
• 负责人: Svecova, Dagmar
• 金额: $ 1.6万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=636475
• 关键词: Improving; durability; joints; precast; decks

The poor state of North American infrastructure has received considerable attention over the last several years. Many of the bridges in Manitoba were built in the 1950s to 1970s. These bridges are approaching the end of their service lives and will need to be replaced or rehabilitated in the near future. The American Society of Civil Engineers reports that 200 million trips in the United States are taken daily across bridges that are deteriorating and may need replacing or strengthening. The cost of replacement or rehabilitation is impacted by the length of time required to complete the upgrade. As a result, Accelerated Bridge Construction (ABC) practices have been developed in recent years. This research proposal focuses on prefabrication of bridge elements, a type of ABC that will further accelerate construction while improving structural safety and durability.Besides accelerating construction, precast bridge deck construction has the advantage of achieving high quality production with tight tolerances. Precast construction increases the long-term durability of concrete as a result of its low permeability, and reduces shrinkage strains thanks to the controlled environment of a precast plant. High performance concrete (HPC) can be used to join the precast panels to shorten the curing time. Therefore, the use of HPC in construction joints is increasing and is often an integral part of ABC.This research will focus on the use of innovative reinforcement methods to produce durable joints for precast bridge deck panels. The current methods of joining precast bridge decks in negative moment regions requires external post-tensioning, in order to prevent cracking of the joint. My research proposes innovative methods to solve the problem. Fibre-reinforced polymer (FRP) prestressed concrete prisms (PCP) will be used to introduce small levels of compression into the joints. This will improve the service load performance by delaying and minimizing cracking, and also will result in much smaller crack widths. FRPs are non-corrosive, therefore the joints will last longer. FRP tendons have been reported to fail without warning during prestressing. To mitigate possible workplace injuries in precast plants using this material, my research will focus on developing of acoustic emission monitoring technique to detect failures of FRP bars during stressing. The warning system will be used for long-term monitoring of stresses in FRP bars, and improving worker safety during stressing operations by detecting and preventing FRP bar rupture due to overstressing and providing warning before FRP bar failure. The practical findings of this research will be useful for bridge engineers, infrastructure owners, and precast contractors. The development of FRP failure warning system has a large potential for improving safety of FRP-reinforced and prestressed structures. The research will provide data for accelerating bridge construction using FRP and prestressed concrete prisms. Accelerated construction reduces traffic interruptions, and the overall cost of construction while improving durability and structural integrity.

过去几年，北美基础设施的落后状况受到了广泛关注。马尼托巴省的许多桥梁建于 20 世纪 50 年代至 1970 年代。这些桥梁的使用寿命即将结束，需要在不久的将来进行更换或修复。美国土木工程师协会报告称，在美国，每天有 2 亿人次穿过正在恶化、可能需要更换或加固的桥梁。更换或修复的成本受到完成升级所需时间的影响。因此，近年来开发了加速桥梁施工（ABC）实践。该研究计划的重点是桥梁构件的预制，这是一种 ABC，将进一步加速施工，同时提高结构安全性和耐久性。除了加速施工之外，预制桥面施工还具有实现高质量生产和严格公差的优势。预制建筑由于其低渗透性而提高了混凝土的长期耐久性，并且由于预制工厂的受控环境而减少了收缩应变。高性能混凝土（HPC）可用于连接预制板以缩短固化时间。因此，HPC 在施工缝中的使用越来越多，并且通常是 ABC 的一个组成部分。本研究将重点关注使用创新的加固方法来生产预制桥面板的耐用接头。目前在负弯矩区域连接预制桥面的方法需要外部后张拉，以防止接头开裂。我的研究提出了解决该问题的创新方法。纤维增强聚合物（FRP）预应力混凝土棱柱（PCP）将用于在接缝中引入小程度的压缩。这将通过延迟和最小化裂纹来提高使用负载性能，并且还将导致裂纹宽度更小。玻璃钢不腐蚀，因此接头的使用寿命更长。据报道，FRP 筋在预应力过程中会在没有警告的情况下失效。为了减少使用这种材料的预制工厂中可能发生的工作场所伤害，我的研究将集中于开发声发射监测技术，以检测 FRP 筋在受力过程中的故障。该预警系统将用于长期监测FRP筋的应力，通过检测和防止FRP筋因应力过大而破裂并在FRP筋失效前发出警告，提高应力操作过程中工人的安全。这项研究的实际结果将对桥梁工程师、基础设施业主和预制承包商有用。 FRP失效预警系统的发展对于提高FRP加固和预应力结构的安全性具有巨大的潜力。该研究将为加速使用玻璃钢和预应力混凝土棱柱的桥梁建设提供数据。加速施工可减少交通中断和总体施工成本，同时提高耐用性和结构完整性。