Bridge reliability under the influence of changing environmental and demand conditions

Lead Research Organisation: University of Surrey
Department Name: Civil and Environmental Engineering

Abstract

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.

Planned Impact

Quantifying the increase in the risk of failure of bridges, in terms of the potential future long-term impacts, brought about through climate change and increasing loading effects will provide an indication of the resilience of existing or planned assets and aid in prioritisation and managent of climate risks. In this regard, the key beneficiaries will be the owner/management authorities of transport infrastructure systems and assets and professional engineers. Estimating the expected costs of climate impacts in a systematic way will enable infrastructure managers to judge the amount of resources they need to allocate for choosing appropriate future adaptation measures ensuring a reliable and robust future transportation network. The recent bridge failures due to severe flooding in Cumbria demonstrated the inter-dependent nature of different infrastructure networks such as electricity, gas, telephone, water supplies etc. with transport. Therefore, quantifying the risk of bridge collapses under the influence of changing environmental and demand conditions has the potential to benefit other services/utilities such as water, power and telecommunications, thus improving our ability to predict/assess the vulnerability and resilience of critical infrastructure. The proposed research project will benefit from collaboration with, and advice from, Network Rail, HR Wallingford, Transport Research Laboratory (TRL) and Tony Gee & Partners (TGP). Understanding and assessing the effects of climate change and increasing loading demands on the bridge stock is of key importance to these organisations in terms of their long-term management and investment decisions. The mix of collaborators allows diverse needs and opinions to be captured, and provides a powerful repository of knowledge/expertise that will be exploited by the project team. Both Network Rail and TGP will participate in the project by attending project meetings and providing technical guidance, input and direction towards the achievement of the objectives. Network Rail will also provide access to relevant records to demonstrate the application of the developed methodology to a number of typical bridge types. HR Wallingford's principal role will be to advise on the selection and interpretation of bridge scour data and modelling techniques, whereas TRL's wide ranging expertise on bridge deterioration and performance assessment will help in the appropriate selection of models and in assessing their potential and their limitations. It is expected that information exchange will take place between the proposed project and a recently initiated research project funded by EPSRC, FUTURENET (Future Resilient Transport Networks). As both HR Wallingford and TRL are amongst the participants of the FUTURENET project, any potential duplication between the two projects will be avoided. It is envisaged that FUTURENET can benefit from the proposed project in terms of the enhanced bridge risk and reliability predictions under the effect of changing climate and load demands. These could be readily introduced into their network reliability model for the estimation of its future resilience. As the overall framework of the proposed project will be risk-based, focusing on consequences and costs of potential bridge failures, it is directly related to the quantification of robustness and resilience of bridge structures, which is the focus of the COST Action TU0601 in which the PI is involved. Therefore, information exchange will take place between the two projects. In addition, the results will also be exploited and disseminated in the form of a technical report and publication of results in internationally acknowledged technical journals and conference proceedings. Through Network Rail and TRL, dissemination of results will be channelled directly to to the bridge owner/management community (e.g. via the Bridge Owners Forum nationally and UIC internationally) as has been done in the past by the PI

Publications

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Description The project has identified the key impacts of climate change on the reliability of bridge structures. A framework that can be used to estimate the time-dependent risk profile of any bridge under changing environmental conditions by quantifying the probability and the consequences of failure has been developed. Focus has been given to the effect of changing environmental parameters (i.e. temperature, humidity, rainfall) and atmospheric pollutants on the deterioration of metallic bridges and the effect of changes in flood magnitudes and frequencies on bridge scour. The results have shown that the potential increase in temperature due to climate change is expected to have only a small influence on the reliability of metallic bridges. The SO2 concentration was found to have the most adverse effect on the reliability of the bridge amongst all climatic and pollutant parameters. It was also shown that although the long-term reduction of SO2 concentration in an area can enhance the reliability and hence reduce the risk of the exposed structure, the time-dependent probability of failure and associated risk remain higher compared to a bridge exposed to a less polluted environment from the beginning of its service-life.
Exploitation Route The developed framework for costing climate change impacts on bridges can offer to decision-makers the opportunity to prioritise and manage climate risks. Estimating the expected costs of climate impacts in a systematic way can enable infrastructure managers to judge the amount of resources they need to allocate for choosing appropriate future adaptation measures. The methodology has the flexibility to be applied at a local, regional and national level The developed methodology offers 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. It is directly applicable in terms of taking into account the uncertainties inherent to climate change predictions and the long-term behaviour of a bridge. The framework can also be utilised to quantify the consequences that climate change and adverse weather events may have on the transportation network.
Sectors Construction,Environment,Transport

 
Description Planning and Asset Management for Climate Change Adaptation
Amount £75,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 10/2012 
End 10/2016