Bridge reliability under the influence of changing environmental and demand conditions

气候变化是未来几年需要应对的一项重要的全球挑战。气候变化既可以被认为是长期平均气候变化带来的长期风险问题，也可以是短期极端事件带来的风险问题。交通基础设施系统旨在长期运行，但在其生命周期内越来越有可能受到气候变化的影响。对未来气候条件的了解对于帮助基础设施所有者管理气候变化对现有基础设施和规划基础设施的影响至关重要。显然有必要将气候变化产生的负面影响降至最低，并通过将其引入当前的设计和评估实践来适应未来预期的变化。从长期来看，未来的负荷增加可能也会变得显著。对气候和不断增加的负载需求对基础设施的影响的风险和成本的改进和更可靠的定义和估计应该是这项工作的基础。拟议的项目是一项倡议，旨在评估预期的气候变化、天气以及对桥梁的负载需求增加的潜在意义，并从桥梁安全、预期故障成本以及额外的维护和适应费用方面量化对现有基础设施构成的风险。该项目将专注于与桥梁冲刷、材料劣化、温度应力循环和移动以及轴承劣化相关的失效模式。将开发一种新的方法来估计在气候变化和不断增加的荷载需求影响下桥梁倒塌的风险。风险的时间演变将通过量化上述每种模式下桥梁随时间发生故障的概率以及对故障后果的量化来获取。一个能够捕捉不确定性的概率框架对于从风险增加(即安全性降低)以及维护、更换和适应计划产生的预期未来额外成本方面量化气候变化对桥梁基础设施的影响至关重要。案例研究首先将重点放在金属桥上，尽管框架可以调整并应用于其他类型的桥梁，如混凝土和砖石结构。拟议的方法将有可能以当地未来气候变化预测的形式纳入投入，并将提供机会为任何给定的桥梁人口建立桥梁风险等级图，该地图描述桥梁结构根据其位置对气候变化和变化的活荷载影响的脆弱性。拟议工作的个别目标确定如下：1.开发一种新的概率方法，用于估计在不断变化的环境和负载需求条件下桥梁坍塌的风险。2.评估气候变化引起的河流洪水增加的影响，评估气候变化和不断增加的活荷载对材料劣化和桥梁可靠性的影响。IV.评估气候变化引起的温度变化对桥梁热运动、应力循环和承载性能的影响。V.应用所开发的方法，以案例研究的形式，评估一些典型桥梁类型的可靠性和倒塌风险。拟议的工作将受益于与Network Rail、TGP、HR Wallingford和TRL等组织的合作，并使它们能够应对与桥梁基础设施长期管理相关的未来挑战。这将允许捕获不同的需求和意见，并提供一个强大的知识/专业知识存储库，供项目团队使用。

Climate change is an important global challenge to be addressed in the coming years. Climate change can be considered as a long-term risk issue brought about by changes in the long-term average climate but also in the short-term extreme events. Transport infrastructure systems, which are designed to be operational over a long time period, are increasingly likely to experience the impact of climate change over their lifetime. Knowledge of future climatic conditions is essential in order to aid infrastructure owners manage the impact of climate change on both existing and planned infrastructure. There is a clear need to minimise the negative impacts arising from the changing climate and adapt to the changes expected in the future by introducing them into current design and assessment practice. In the long term, future load increases are likely to become significant as well. An improved and more reliable definition and estimation of the risk and costs of climate and increasing loading demand impacts on infrastructure should underpin this effort.The proposed project is an initiative to evaluate the potential significance of the anticipated changes to climate, weather as well as increasing load demand on bridges and to quantify the risks posed to the existing infrastructure in terms of bridge safety, expected failure costs and additional maintenance and adaptation expenses. The project will focus on failure modes associated with bridge scour, material deterioration, temperature stress cycling and movement and bearing deterioration. A novel methodology for estimating the risk of collapse of bridges under the effect of changing climate and increasing loading demands will be developed. The time evolution of risk will be captured through quantifying the probability of failure of the bridge over time for each of the above mentioned modes as well as quantification of the consequences of failure. A probabilistic framework, which is able to capture uncertainties, is essential towards quantifying the effects of climate change on the bridge infrastructure in terms of the increase in risk, i.e. reduction in safety, as well in terms of expected additional future costs arising from maintenance, replacements and adaptation plans. Case studies will at first focus on metallic bridges, though the framework could be adapted and applied to other bridge types such as concrete and masonry. The proposed methodology will have the potential to incorporate input in the form of local future climate change predictions and will offer the opportunity to establish a bridge risk ranking map for any given bridge population characterising the vulnerability of a bridge structure, depending on its location, to climate change and changing live load effects.The individual objectives of the proposed work are identified as follows:I. Development of a novel probabilistic methodology for the estimation of risk of collapse of bridges under changing environmental and load demand conditions.II. Evaluation of the effect of increased river flooding, arising from climate change, on the scour risk ranking and reliability of bridges.III. Evaluation of the effects of climate change and increasing live loading on material deterioration and bridge reliability.IV. Evaluation of the effects of temperature changes due to climate change on bridge thermal movements, stress cycling and bearing performance. V. Application of the developed methodology, in the form of case studies, for the estimation of the reliability and risk of collapse of a number of typical bridge types.The proposed work will benefit from collaboration with a mix of organisations i.e. Network Rail, TGP, HR Wallingford and TRL and will allow them to meet the future challenges associated with the long-term management of bridge infrastructure. This will allow diverse needs and opinions to be captured, and provides a powerful repository of knowledge/expertise that will be exploited by the project team.