Multi-hazard probabilistic risk assessment of bridge networks in cold regions

最近发生的自然和人为灾害突出表明，民用基础设施易受极端事件的影响，并对受灾社区造成严重的社会和经济破坏。为了解决这个问题，工程师们正在转向概率风险评估方法，以更好地考虑桥梁生命周期固有的不确定性。此外，由于气候变化，加拿大的公路桥梁正在经历洪水、冰冲击和地基冲刷等自然灾害的程度和频率增加。尽管工程师和决策者多年来采用了更复杂的方法来分析和评估桥梁，但概率方法的使用仅限于少数桥梁构件的分析。因此，目前尚不清楚其他关键桥梁元件特性的变化如何影响这些结构的整体性能和安全性。当桥梁受到多种危害时，这种知识的缺乏就更加突出了。我的研究计划的总体目标是通过评估典型公路桥梁的整体性能以及三种最常见的桥梁危害（超载、冲击和冲刷）的失效后果来缩小这一差距。在世界范围内，这三种危害加起来约占所有桥梁故障的90%。特别是在加拿大这样的寒冷地区，由于冰冻周期和冰塞，冲刷对桥梁基础的影响更加突出。由于自然季节性和气候变化，水冻结也增加了洪水的风险，碎片和水压增加的影响使桥梁故障的可能性更高。此外，如果我们考虑到加拿大约45%的桥梁已经达到其预期寿命，并且维护和修复的总体预算仅涵盖估计成本的约59%，那么通过基于概率风险的方法来解决公路桥梁的安全问题是在地方和国家网络层面优化分配这些经济资源的唯一可行替代方案。我的研究计划的短期目标将是开发计算效率高的评估工具，用于公路桥梁的风险，使用上述危害的基于神经网络的方法。第二，将考虑加拿大公路网和城市发展的主要特点，评估桥梁故障的社会和经济后果。我的研究的长期目标是开发一个框架，以支持决策过程，将解决所有的桥梁危险。这项研究计划对社会的直接好处是培养高素质的人才。在我的监督下，学生和执业工程师将获得桥梁概率风险评估领域的最先进技能，为SNC-Lavalin，Stantec和马尼托巴基础设施等加拿大集团提供新的宝贵专业知识。

Recent natural and man-made disasters have highlighted the vulnerability of civil infrastructures to extreme events and the resulting severe social and economic disruption to the affected communities. To address this issue, engineers are moving towards probabilistic risk assessment methods to better account for the uncertainties inherent to bridge life-cycles. Also, due to climate change, Highway bridges in Canada are experiencing increased magnitudes and frequencies of natural hazards such as flooding, ice impact and foundation scours. Even though engineers and decision-makers have over the years adopted more sophisticated methods for the analysis and evaluation of bridges, the use of probabilistic methods has been limited to the analysis of few bridge components. As a consequence, it is still not clear how changes in the characteristics of other key bridge elements affect the overall performance and safety of these structures. This lack of knowledge is even more emphasised when bridges are subject to multiple hazards. The overall objective of my research program is to reduce this gap by assessing the overall performance of typical highway bridges and the consequences of failure for three of the most common bridge hazards, which are overloading, impact and scour. Worldwide, these three hazards combined account for about 90% of all bridge failures. In particular, in cold regions like Canada, the effect of scour on bridge foundations is even more accentuated due to freezing cycles and ice jams. Water freezing, due to natural seasonality and climate change, also increases the risk of flooding with higher chances of bridge failure by impact of debris and increased water pressure. Furthermore, if we consider that in Canada about 45% of bridges have already reached their life expectancy and that the overall budget for maintenance and rehabilitation only covers about 59% of the estimated cost, addressing the safety of highway bridges with a probabilistic risk-based approach is the only viable alternative for the optimal allocation of these economic resources at a local and national network levels. The short-term goals of my research program will be to develop computationally efficient assessment tools for the risk of highway bridges using a scenario-based approach for the aforementioned hazards. Second, social and economic consequences of bridge failure will be evaluated considering key characteristics of the Canadian highway network and urban developments. The long-term goal of my research is to develop a framework to support decision-making processes that will address all bridge hazards. An immediate benefit to society of this research program is the training of highly qualified personnel. Under my supervision, both students and practising engineers will gain state-of-the-art skills in the area of probabilistic risk assessment of bridges offering new valuable expertise to Canadian groups, like SNC-Lavalin, Stantec and Manitoba Infrastructure.