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The Science Behind Scour at Bridge Foundations: a Review

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The Science Behind Scour at Bridge Foundations: a Review water Review The Science behind Scour at Bridge Foundations: A Review Alonso Pizarro 1,* , Salvatore Manfreda 1,2 and Enrico Tubaldi 3 1 Department of European and Mediterranean Cultures, University of Basilicata, 75100 Matera, Italy; [email protected] 2 Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, via Claudio 21, 80125 Napoli, Italy 3 Department of Civil and Environmental Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, UK; [email protected] * Correspondence: [email protected]; Tel.: +44-7517-865-662 Received: 14 December 2019; Accepted: 22 January 2020; Published: 30 January 2020 Abstract: Foundation scour is among the main causes of bridge collapse worldwide, resulting in significant direct and indirect losses. A vast amount of research has been carried out during the last decades on the physics and modelling of this phenomenon. The purpose of this paper is, therefore, to provide an up-to-date, comprehensive, and holistic literature review of the problem of scour at bridge foundations, with a focus on the following topics: (i) sediment particle motion; (ii) physical modelling and controlling dimensionless scour parameters; (iii) scour estimates encompassing empirical models, numerical frameworks, data-driven methods, and non-deterministic approaches; (iv) bridge scour monitoring including successful examples of case studies; (v) current approach for assessment and design of bridges against scour; and, (vi) research needs and future avenues. Keywords: scour; bridge foundations; Natural Hazards; floods 1. Introduction “If a builder builds a house for a man and does not make its construction firm, and the house which he has built collapses and causes the death of the owner of the house, that builder shall be put to death. If it causes the death of a son of the owner of the house, they shall put to death a son of that builder. If it causes the death of a slave of the owner of the house, he shall give to the owner of the house a slave of equal value. If it destroys property, he shall restore whatever it destroyed, and because he did not make the house, which he built, firm, and it collapsed, he shall rebuild the house that collapsed from his own property (i.e., at his own expense).” —The Code of Hammurabi about 2250 B.C. [1] Human-made structures and infrastructure are objects of continuous improvement due to their importance and role in society. Going beyond current practices for increasing their safety has been recognized as a fundamental issue for thousands of years. The Hammurabi code is an example of a regulating framework for ensuring the safety of structures, by punishing builders of faulty constructions [1,2]. Since times immemorial, bridges have been (and still are) a challenge for architects, engineers, and builders. This challenge covers all the phases from design to construction, maintenance, monitoring, and rebuilding. Failing bridges may cause severe disruption to infrastructure networks, social and economic problems, possible cultural-heritage losses, and on some occasions, many casualties. Scour from sediments around bridge foundations is one of the greatest threats to bridge safety. Water 2020, 12, 374; doi:10.3390/w12020374 www.mdpi.com/journal/water Water 2020, 12, 374 2 of 26 Water 2020, 12, 374 2 of 26 Scour is an erosional process that can occur in rivers due to the interaction between any type of structure located underwater and the river flow. It is by far the leading cause of bridge failure worldwideScour is[3–8], an erosional resulting process in significant that can direct occur losses in rivers and duedisruption to the interactionto road networks between in anyterms type of oftransportation structure located operation, underwater petrol, andhigh thetraffic, river addi flow.tional It is laborers by far thedue leading to temporary cause ofclosure, bridge detours failure worldwideto the network [3–8 ],road, resulting and reconstruction in significant directworks losses[9–11]. and In disruptionEurope, bridges to road and networks road infrastructure in terms of transportationreparations due operation, to the 2002 petrol, flood high in Germany traffic, additional amounted laborers to €577 due million to temporary [12], while closure, the Austrian detours toFederal the network Railways road, operator, and reconstruction ÖBB, faced economic works [losse9–11].s of In about Europe, €100 bridges million and due road to flooding infrastructure [13]. In reparationsthe U.K., 20 dueroad tobridges the 2002 were flood partially in Germany or totally amounted destroyed to due¿577 to millionflood events [12], in while 2009 the [14], Austrian having Federalestimated Railways financial operator, losses about ÖBB, £2 faced million economic per week. losses Additionally, of about ¿ the100 costs million for scour due to risk flooding mitigation [13]. Inis estimated the U.K., 20 at road€541 bridgesmillion wereper year partially for the or totallyperiod destroyed2040–2070 due in Europe to flood [15]. events In inturn, 2009 in [ 14the], U.S.A., having estimateddamages to financial bridges losses and highways about £2 millionfrom major per week.floods Additionally,in 1964 and 1972 the costsamounted for scour to $100 risk million mitigation per isevent estimated [16], and at ¿ the541 Federal million Highway per year for Administration the period 2040–2070 (FHWA) in estimated Europe [ 15that,]. In on turn, average, in the 50 U.S.A., to 60 damagesbridges collapse to bridges each and year highways in the country from major [17]. In floods New in Zealand, 1964 and it 1972was estimated amounted that to $100 scour million damages per eventare about [16], 36 and million the Federal NZ $/year Highway [18]. In Administration Iran, the financial (FHWA) losses estimated due to bridge that, oncollapse average, reached 50 to the 60 bridgescost of US collapse $562.5 each million year in in the the first country decade [17 of]. the In New 21st century Zealand, [19], it was while estimated the estimated that scour annual damages value areof scour about damage 36 million in South NZ $ /Africayear [18 amounts]. In Iran, 22 themillion financial South losses African due Rands to bridge (ZAR) collapse [20]. Additionally, reached the costthe damage of US $562.5 of the million flood in the2007 first to transport decade of infr theastructure 21st century in [Bangladesh19], while the and estimated Indonesia annual amounted value ofto scour34% and damage 25% inof Souththe total Africa infrastructure amounts 22 costs million (US South$363 million African and Rands US (ZAR)$35 million, [20]. Additionally, respectively the[21]). damage of the flood in 2007 to transport infrastructure in Bangladesh and Indonesia amounted to 34% andFigure 25% 1 shows of the totalnotable infrastructure examples of costs bridges (US that $363 collapsed million and dueUS to scour $35 million, in two different respectively countries [21]). that Figureare severely1 shows affected notable by examples floods ofevery bridges year, that Italy collapsed and the due U.K. to scourAmong in two the didifferentfferent countriestypes of thatbridges, are severely masonry aff archected bridges by floods are every the year,most Italy vulnerable and the U.K.because Among they the are di oftenfferent built types on of shallow bridges, masonryfoundations arch and bridges have are a therigid most behavior vulnerable that becauseis sensitive they to are settlements often built on[22]. shallow The collapse foundations of these and havebridges a rigid caused behavior not only that significant is sensitive direct to settlements and indire [22ct]. Theeconomic collapse losses, of these but bridges also losses caused of notcultural only significantheritage. direct and indirect economic losses, but also losses of cultural heritage. Figure 1. (A) Rubbianello Bridge, Rubbianello, Italy; (B) Copley Bridge, Halifax, U.K. (courtesy of CalderdaleFigure 1. (A Metropolitan) Rubbianello Borough Bridge, Council).Rubbianello, Italy; (B) Copley Bridge, Halifax, U.K. (courtesy of Calderdale Metropolitan Borough Council). This paper aims to present an up-to-date state-of-the-art review on bridge scour. Section2 briefly reviewsThis the paper diff erentaims to types present of scour an up-to-date and the physics state-of-the-art of sediment review particle on bridge motion. scour. Section Section3 describes 2 briefly thereviews controlling the different scour types dimensionless of scour and parameters; the physics physical of sediment modelling; particle bridge motion. scour Section estimates 3 describes based ontheempirical, controlling numerical, scour dimensionless and data-driven parameters; approaches; physical and, modelling; non-deterministic bridge scour frameworks. estimates Sectionbased on4 showsempirical, the recentnumerical, advancements and data-d inriven terms approaches; of scour measurements and, non-deterministic and bridge frameworks. monitoring. Section 54 dealsshows with the therecent current advancements approach forin terms assessment of scou andr measurements design of bridges and againstbridge scour,monitoring. while Section 65 discussesdeals with research the current needs approach and future for directions.assessment and design of bridges against scour, while Section 6 discusses research needs and future directions. Water 2020, 12, 374 3 of 26 Water 2020, 12, 374 3 of 26 2. Processes and Definitions 2. Processes and Definitions 2.1. Different Types of Scour 2.1. Different Types of Scour Scour is an erosional
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