Vulnerability of bridges to scour: insights from an international expert elicitation workshop

Abstract. Scour (localised erosion) during flood events is one of the most significant threats to bridges over rivers and estuaries, and has been the cause of numerous bridge failures, with damaging consequences. Mitigation of the risk of bridges being damaged by scour is therefore important to many infrastructure owners, and is supported by industry guidance. Even after mitigation, some residual risk remains, though its extent is difficult to quantify because of the uncertainties inherent in the prediction of scour and the assessment of the scour risk. This paper summarises findings from an international expert workshop on bridge scour risk assessment that explores uncertainties about the vulnerability of bridges to scour. Two specialised structured elicitation methods were applied to explore the factors that experts in the field consider important when assessing scour risk and to derive pooled expert judgements of bridge failure probabilities that are conditional on a range of assumed scenarios describing flood event severity, bridge and watercourse types and risk mitigation protocols. The experts' judgements broadly align with industry good practice, but indicate significant uncertainty about quantitative estimates of bridge failure probabilities, reflecting the difficulty in assessing the residual risk of failure. The data and findings presented here could provide a useful context for the development of generic scour fragility models and their associated uncertainties.

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Vulnerability of bridges to scour: insights from an international expert elicitation workshop

10.5194/nhess-2016-350 ◽

2016 ◽

Cited By ~ 1

Author(s):

Rob Lamb ◽

Willy Aspinall ◽

Henry Odbert ◽

Thorsten Wagener

Keyword(s):

Risk Mitigation ◽

Good Practice ◽

Expert Elicitation ◽

Residual Risk ◽

Bridge Scour ◽

International Expert ◽

Quantitative Estimates ◽

Bridge Failure ◽

Expert Workshop ◽

Failure Probabilities

Abstract. Scour (localised erosion) during flood events is one of the most important threats to bridges over rivers and estuaries, and has been the cause of numerous bridge failures, with damaging consequences. Mitigation of the risk of bridges being damaged by scour is therefore important for many infrastructure owners, and is supported by industry guidance. Even after mitigation, some residual risk remains, though its extent is difficult to quantify because of the uncertainties inherent in the prediction of scour and the assessment of the scour risk. This paper summarises findings of an international expert workshop on bridge scour risk assessment exploring uncertainties about the vulnerability of bridges to scour. Two specialised structured elicitation methods were applied to explore the factors that experts in the field consider important in assessing scour risk, and to derive pooled expert judgements of bridge failure probabilities conditional on a range of assumed scenarios describing flood event severity, bridge and watercourse types and risk mitigation protocols. The experts' judgements broadly align with industry good practice, but indicate significant uncertainty about quantitative estimates of bridge failure probabilities, reflecting the difficulty in assessing the residual risk of failure. The data and findings presented here could provide useful context for the development of generic scour fragility models, and their associated uncertainties.

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A Framework for Risk-Based Cost–Benefit Analysis for Decision Support on Hydrogeological Risks in Underground Construction

Geosciences ◽

10.3390/geosciences11020082 ◽

2021 ◽

Vol 11 (2) ◽

pp. 82

Author(s):

Johanna Merisalu ◽

Jonas Sundell ◽

Lars Rosén

Keyword(s):

Decision Support ◽

Cost Benefit Analysis ◽

Risk Mitigation ◽

Ground Surface ◽

Cost Benefit ◽

Expert Elicitation ◽

Benefit Analysis ◽

Underground Construction ◽

Groundwater Leakage ◽

Risk Reducing

Construction below the ground surface and underneath the groundwater table is often associated with groundwater leakage and drawdowns in the surroundings which subsequently can result in a wide variety of risks. To avoid groundwater drawdown-associated damages, risk-reducing measures must often be implemented. Due to the hydrogeological system’s inherent variability and our incomplete knowledge of its conditions, the effects of risk-reducing measures cannot be fully known in advance and decisions must inevitably be made under uncertainty. When implementing risk-reducing measures there is always a trade-off between the measures’ benefits (reduced risk) and investment costs which needs to be balanced. In this paper, we present a framework for decision support on measures to mitigate hydrogeological risks in underground construction. The framework is developed in accordance with the guidelines from the International Standardization Organization (ISO) and comprises a full risk-management framework with focus on risk analysis and risk evaluation. Cost–benefit analysis (CBA) facilitates monetization of consequences and economic evaluation of risk mitigation. The framework includes probabilistic risk estimation of the entire cause–effect chain from groundwater leakage to the consequences of damage where expert elicitation is combined with data-driven and process-based methods, allowing for continuous updating when new knowledge is obtained.

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“Radiobiology of Proton Therapy”: Results of an international expert workshop

Radiotherapy and Oncology ◽

10.1016/j.radonc.2018.05.018 ◽

2018 ◽

Vol 128 (1) ◽

pp. 56-67 ◽

Cited By ~ 39

Author(s):

Armin Lühr ◽

Cläre von Neubeck ◽

Jörg Pawelke ◽

Annekatrin Seidlitz ◽

Claudia Peitzsch ◽

...

Keyword(s):

Proton Therapy ◽

International Expert ◽

Expert Workshop

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Current debates on end-of-life sedation: an international expert elicitation study

Supportive Care in Cancer ◽

10.1007/s00520-014-2200-9 ◽

2014 ◽

Vol 22 (8) ◽

pp. 2141-2149 ◽

Cited By ~ 35

Author(s):

Evangelia Papavasiliou ◽

◽

Sheila Payne ◽

Sarah Brearley

Keyword(s):

End Of Life ◽

Expert Elicitation ◽

International Expert ◽

Elicitation Study

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international-expert-workshop-on-the-world-heritage-convention-and-indigenous-peoples;hr

Human Rights Documents online ◽

10.1163/2210-7975_hrd-1031-3001 ◽

2016 ◽

Keyword(s):

Indigenous Peoples ◽

World Heritage ◽

International Expert ◽

World Heritage Convention ◽

The World ◽

Expert Workshop

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International expert workshop on the analysis of the economic and public health impacts of air pollution: workshop summary.

Environmental Health Perspectives ◽

10.1289/ehp.021101163 ◽

2002 ◽

Vol 110 (11) ◽

pp. 1163-1168 ◽

Cited By ~ 20

Author(s):

Michelle L Bell ◽

Devra Davis ◽

Luis Cifuentes ◽

Aaron Cohen ◽

Nelson Gouveia ◽

...

Keyword(s):

Public Health ◽

Air Pollution ◽

Health Impacts ◽

International Expert ◽

Workshop Summary ◽

Expert Workshop

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Simulations of Local Scour Around a Cylindrical Bridge Pier And a Semicircular Abutment Using Unsteady k-ε Model Combined with σ-Grid

The Open Civil Engineering Journal ◽

10.2174/1874149501711010598 ◽

2017 ◽

Vol 11 (1) ◽

pp. 598-614

Author(s):

Shi Liu ◽

Yi Yang ◽

Xiaobo Wu

Keyword(s):

Transport Model ◽

Flow Fields ◽

Local Scour ◽

Bridge Scour ◽

Complex Flow ◽

Numerical Result ◽

Load Transport ◽

Reasonable Prediction ◽

Commercial Solver ◽

Bridge Failure

Introduction: Bridge scour is one of the major causes of bridge failure. Prediction of the maximum depth and shape of local scour plays an important role in bridge design and maintenance. In this paper, k-ε turbulent model combined with wall function was employed and complex flow fields are exhibited. The bed load transport model summarized by Qian and Wan [1] was applied to evaluate the development of local scour. Besides, σ-grid module was developed and embedded into the commercial solver FLUENT to fit the change of channel-bed. Method: In this module, the change of the elevation of the channel bed is calculated through using user defined functions(UDF), and the motion of the grid system is realized based on a program developed through C++ language, which extends the applications of FLUENT. The evolution of local scour hole for two cases, i.e., local scour around a cylindrical pier and a semicircular abutment, was simulated. Results and Conclusion: The depth and the shape of local scour as well as the flow fields were predicted. Numerical result conforms well to the experimental measurement. Especially, it provides fairly reasonable prediction on the key issue of the maximum scour depth. The satisfactory agreement validates the numerical method developed in the present study. In addition to the validation purpose, the different performance of this method for predicting local scour around the cylindrical pier and the semicircular abutment was discussed.

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On the potential for using bridge natural frequencies to detect scour: an experimental study

IABSE Congress, Christchurch 2021: Resilient technologies for sustainable infrastructure ◽

10.2749/christchurch.2021.0293 ◽

2021 ◽

Author(s):

Kasun Kariyawasam ◽

Campbell Middleton ◽

James Talbot ◽

Paul Fidler ◽

Stuart Haigh ◽

...

Keyword(s):

Natural Frequency ◽

Natural Frequencies ◽

Repair Process ◽

Small Scale ◽

Bridge Scour ◽

Dense Sand ◽

Geotechnical Centrifuge ◽

Bridge Model ◽

Experimental Findings ◽

Bridge Failure

Monitoring bridges for precursors of failure has the potential to improve their safety and resilience. However, the most prominent cause of bridge failure, scour, is difficult to monitor as it occurs underwater. The potential to identify scour by monitoring changes in the natural frequencies of a bridge is studied experimentally in this research. A field study was carried out on a bridge with pre- existing scour confined to a section of a piled pier foundation, which was monitored throughout a repair process involving controlled backfilling of the scoured region, i.e. scour in reverse. The changes in natural frequency due to backfilling of the scour hole were unable to be captured experimentally as the estimated magnitudes (9% and 6 % for the first and second modes respectively) were of the same order as the variability of the natural frequency estimates. In order to study the relationship between natural frequency and scour in a more controlled environment, a geotechnical centrifuge experiment was conducted to simulate scour in a small-scale integral bridge model in dense sand. The model showed a significant (up to 40 %) change in natural frequency as a result of a scour depth equivalent to 30 % of the piled foundation depth. These experimental findings suggest that natural frequencies can potentially aid in detecting extensive bridge scour for piled foundations, but it may be challenging to detect localised scour limited to only a small portion of a foundation.

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Manuscript review of “Vulnerability of bridges to scour: insights from an international expert elicitation workshop” by Lamb et al.

10.5194/nhess-2016-350-rc1 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Expert Elicitation ◽

International Expert ◽

Manuscript Review

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Key elements to assess proposals for rockfall risk mitigation in the context of a technical and economic feasibility project – the experience of two alpine italian regions

10.5194/egusphere-egu2020-5753 ◽

2020 ◽

Author(s):

Claudia Strada ◽

Davide Bertolo ◽

Volkmar Mair ◽

Marco Paganone

Keyword(s):

Risk Assessment ◽

Risk Mitigation ◽

Project Managers ◽

Residual Risk ◽

Mitigation Measures ◽

Risk Level ◽

Acceptable Risk ◽

Italian Regions ◽

Geological Conditions ◽

Hazard And Risk

The Valle d'Aosta&#160;Region and the Autonomous Province of Bolzano&#160;territories include&#160;the highest mountain areas of Italy,&#160;where most of the communication&#160;infrastructures or strategic activities are&#160;totally or in part partially&#160;exposed&#160;to the&#160;rockfall&#160;hazards.&#160;&#160;For this&#160;reason,&#160;the two administrations&#160;have&#160;established&#160;an operational&#160;cooperation in order&#160;to&#160;compare their procedures and to define&#160;the&#160;criteria&#160;and best practices to prioritize and project the&#160;mitigation the rockfall mitigation measures.&#160;The result achieved by the work group have inspired a new incoming version of the Italian technical standard UNI 11211 &#8220;Rockfall protective measures&#8221;.&#160;&#160;&#160;As&#160;a&#160;part of the&#160;rockfall risk&#160;assessment&#160;of the&#160;designing&#160;the&#160;mitigation measures, it is necessary to&#160;assess the actual&#160;effectiveness&#160;of the alternative&#160;mitigation options which have been identified.&#8239;&#160;The choice whether to mitigate the event intensity or the expected damage, with either&#160;structural or non-structural measures,&#160;will usually achieve a risk mitigation level, associated to a complimentary residual risk.&#160;Therefore, the project management has to evaluate the degree of hazard and risk mitigation for any given solution. The acceptability of the residual risk and its possible mitigation through organizational measures are to be evaluated as well. A long-term cost/benefit analysis has to be performed, taking also into account the tolerability over time of the handling costs.&#160;The first milestone in the decisional process the definition of the acceptable risk level. As a matter of fact, which is the key criterion supporting the decision to undertake cost-effective investments in mitigation works. For that reason, a preliminary analysis of the&#160;in-situ&#160;geological conditions should be as complete and detailed as possible. Project managers have to be aware that the zero-option has to be taken in to&#160;account as well, in the case the risk level would not be acceptable.&#160;Moreover, it has to be taken into account that the risk evaluation&#160;is&#160;always site-specific, because&#160;the rockfall&#160;mitigation projects have to be based on a detailed geological reference model. Local changes in geological, hydrogeological, morphological and structural conditions, vegetation, vulnerability and exposure of the objects at risk&#160;may lead to different hazard and risk conditions even&#160;at a local scale. Therefore, a risk assessment analysis is consistent to a single project and can&#8217;t be directly upscaled to implement, for instance,&#160;a municipal land management plan.&#160;&#160;&#160;Another key point in the decision-making process&#160;is the expected damage assessment, which has to include not only the direct damages (e.g.: loss of human lives) but also the indirect damages and their economic and social impacts. As a consequence, in assessing the acceptable risk&#160;both the probability of direct and indirect damage and the economic and social benefits derived from its acceptance have to be weighted.&#160;The final result has led to guidelines based on QRA (Quantitative Risk Assessment) method and defining three risk levels:&#160;Acceptable, ALARP (As Low&#160;As&#160;Reasonably Practicable) and Unacceptable, providing to the project managers a rational&#160;and objective framework to manage rockfall hazards in Italy.&#160;

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