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Stability of short-span bridges subject to overtopping during floods: Case Studies from UK/Ireland an the USA

Ryan, Donal, Ettema, Rob, Solan, Brian, Hamill, Gerry and McRobert, John (2015) Stability of short-span bridges subject to overtopping during floods: Case Studies from UK/Ireland an the USA. In: 36th IAHR World Congress. IAHR World Congress. 11 pp. [Conference contribution]

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URL: http://app.iahr2015.info/programma_details/3466

Abstract

As a consequence of increased levels of flooding, largely attributable to urbanization of watersheds (and perhaps climate change, more frequent extreme rainfall events are occurring and threatening existing critical infrastructure. Many of which are short-span bridges over relatively small waterways (e.g., small rivers, streams and canals). Whilst these short-span bridges were designed, often many years ago, to pass relatively minor the then standard return-period floods, in recenttimes the failure incidence of such short-span bridges has been noticeably increasing. This is suggestive of insufficient hydraulic capacity or alternative failure mechanism not envisaged at the time of design e.g. foundation scour or undermining. This paper presents, and draws lessons, from bridge failures in Ireland and the USA. For example, in November 2009, the UK and Ireland were subjected to extraordinarily severe weather conditions for several days. The resulting flooding led to the collapse of three UK bridges that were generally 19th century masonry arch bridges, withrelatively shallow foundations. Parallel failure events have been observed in the USA. To date, knowledge of the combined effect of waterway erosion, bridge submergence, and geotechnical collapse has not been adequately studied. Recent research carried out considered the hydraulic analysis of short span bridges under flood conditions, but no consideration was given towards the likely damage to these structures due to erosive coupling of hydraulic and geotechnical factors. Some work has been done to predict the discharge downstream of an inundated arch, focusing onpredicting afflux, as opposed to bridge scour, under both pressurized and free-surface flows, but no predictive equation for scour under pressurized conditions was ever considered. The case studies this paper presents will be augmented by the initial findings from the laboratory experiments investigating the effects of surcharged flow and subsequent scour within the vicinity of single span arch bridges. Velocities profiles will be shown within the vicinity of the arch, in addition to the depth of consequent scour, for a series of flows and model spans. The data will be presented and correlated to the most recent predictive equations for submerged contraction and abutment scour. The accuracy of these equations is examined, and the findings used as a basis for developing further studies in relation to short span bridges.

Item Type:Conference contribution (Paper)
Keywords:Bridge waterway hydraulics, hydraulic structures, rivers
Faculties and Schools:Faculty of Art, Design and the Built Environment
Faculty of Art, Design and the Built Environment > School of the Built Environment
Research Institutes and Groups:Built Environment Research Institute
Built Environment Research Institute > Studies Allied to Built Environment Research (SABER)
ID Code:32187
Deposited By: Dr Brian Solan
Deposited On:10 Aug 2015 09:15
Last Modified:17 May 2017 09:47

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