Applicationo f Rectangulara nd Circular Collarsa roundB ridgeP ier asa Scour Countermeasure

Every year due to river floods a geat number of river structues such as bridge piers are collapsed. The mosti mportantr easonfo t failure of bridgep iersi s the occunenceo f scourp henomenoant the bottomo f theses tructuresO. ne methodo f scourc ountermeasuirse to set a protectived evice(ie. coliar) around bridge pier. collars protect efficiently the riverbed against vortices system around pier and reduces couring.I.n this researcht,h e performanceo f serieso f rectangulacr ollarsw ith differents izer atio (i.e. WD =1.5,2,2.5) which seatedh orizontallyin differente levations(y "/D: - 0.2, 0, 0.2) in respectt o bed level were investigatedE. xperimentsc arriedo ut under clear-waterconditiona ndt he resultsw erec omparedw ith pier withoutc ollar andp ier with circularc ollar' 'Ihe esults showed that the collar resting on and below the bed level have better effrciency compared with the collar restinga bovet he bed level. As the width of collar increasedt,h e performanceo f collar as a scourc ountermeasuraels o increasedC. ollarsw ith size ratio (WD) of l'5,2 and2'5 reduceds couring 14,29a nd4 9 percentr espectivelyT. he resultsa lsoi ndicatedt hat performance of rectangulacr ollar in reducings courd eptha nd increasinge quilibfiumt ime is bettert han circular one.