Reliability- and Mechanics-based Evaluation of Concrete Building Infrastructure

改善基础设施环境可持续性的举措必须包括对现有建筑物进行更准确的评估和修复，因为这些建筑物含有大量的隐含能量，不应因拆除而浪费。此外，2012年埃利奥特湖阿尔戈马购物中心的倒塌以及随后安大略省专业工程师于2016年出版的结构状况评估指南强调了改进评估措施对加拿大社会的关键重要性。这一需求已经得到美国混凝土协会的独立认可，该协会于2006年成立了技术委员会562《混凝土建筑的评估、维修和恢复》，为现有混凝土结构制定新的规范，并于2013年首次发布。同时，对更高强度混凝土和钢材的不断推动使结构更容易出现适用性问题。最近的举措显著提高了混凝土结构瞬时挠度的准确性，但准确预测混凝土收缩和徐变引起的随时间变化的挠度的方法仍然难以实现。拟议研究计划的长期目标是改进评估、修复和管理现有基础设施以及评估混凝土结构适用性的实践。这些对于工程师做出合理的设计、维护、维修和更换决策是必要的，这将确保加拿大的基础设施得到安全、可持续和经济的管理。因此，拟议研究计划的短期目标是开发新一代基于可靠性和力学的程序，用于对现有混凝土建筑基础设施进行合理的安全评估，支持当前的混凝土标准，并制定改进的标准，用于预测承受持续荷载的混凝土结构的随时间变化的挠度。设想了六个短期目标，涉及5个USRA、8个MESc和1个博士生：(1)当前评估实践中隐含的基准安全水平；(2)制定基于后果的目标可靠性水平和相关评估标准；(3)评估设计寿命缩短对特定瞬时荷载的影响；(4)在量化现有结构的可靠性时，考虑验证荷载试验结果的不确定性；(5)量化当新浇筑的混凝土不到一周的冲击时间偏差时，如何应用荷载；以及，(6)推导出预测混凝土收缩和蠕变引起的随时间变化的挠度的不同因素。所提出的研究将为评估混凝土建筑基础设施的安全性和适用性提供新一代工具。

Initiatives to improve the environmental sustainability of infrastructure must include more accurate assessment and rehabilitation of existing structures because they contain tremendous quantities of embodied energy that should not be wasted through demolition. Moreover, the 2012 collapse of the Algoma Mall in Elliot Lake and the subsequent Professional Engineers Ontario publication of structural condition assessment guidelines in 2016 emphasizes the critical importance of improved assessment measures to Canadian society. This need has independently been recognized by the American Concrete Institute, which formed Technical Committee 562 “Evaluation, Repair and Rehabilitation of Concrete Buildings” in 2006 to develop a new code for existing concrete structures, first published in 2013.Meanwhile, the continuous drive to higher strength concrete and steel materials has made structures more susceptible to serviceability problems. Recent initiatives have markedly improved the accuracy of instantaneous deflections of concrete structures, but means to predict accurately the time-dependent deflections due to concrete shrinkage and creep remain elusive.The long-term goal of the proposed research program, spawned by the Applicant's previous research and industrial experience, is to enhance practices for assessing, rehabilitating and managing existing infrastructure and for assessing the serviceability of concrete structures. These are necessary for engineers to make rational design, maintenance, repair and replacement decisions that will ensure Canada's infrastructure is managed safely, sustainably and economically.The short-term objectives of the proposed research program are therefore to develop a new generation of reliability- and mechanics-based procedures for the rational safety assessment of existing concrete building infrastructure, to support current concrete standards, and to develop improved criteria for predicting the time-dependent deflection of concrete structures subjected to sustained loads. Six short-term objectives involving 5 USRA, 8 MESc, and 1 PhD students are envisaged: (1) benchmark safety levels implicit in current assessment practices; (2) develop consequence-based target reliability levels and associated assessment criteria; (3) assess the impact of reduced design life on specified transient loadings; (4) account for the uncertainty of proof-load test results in the quantification of the reliability of an existing structure; (5) quantify how loadings applied when newly placed concrete is less than a week old impact time-dependent deflections; and, (6) derive distinct factors for predicting the time-dependent deflections due to concrete shrinkage and creep.The proposed research will provide the next generation of tools for assessing the safety and serviceability of concrete building infrastructure.