PSI - Issue 84

Maria Giovanna Tanda et al. / Procedia Structural Integrity 84 (2026) 272–279

279

as for round-nosed rectangular piers with a shape ratio of L / b =3 and a collar embedded 2 cm below the bed surface ( d / b =0.66) − the maximum scour depth is reduced by 50% compared to the no-collar condition, with maximum erosions only slightly greater than the depth at which the collar is installed below the bed. Conversely, other configurations demonstrated lower effectiveness, with the collar unable to fully stabilize scour over time. Nonetheless, in all cases, the temporal progression of erosion was notably delayed relative to the reference (no-collar) condition. The variations observed with slight modifications to the shape factor of the round-nosed rectangular piers indicate that the optimal collar depth position and lateral extent are closely interrelated and strongly influenced by the pier’s geometry. Consequently, the authors plan to expand the experimental program to systematically investigate not only the collar depth position but also its lateral extension, within practical constraints. Acknowledgements This study was developed within the PRIN project FIRMITAS “multi-hazard assessment, control and retroFIt of bridges for enhanced Robustness using sMart IndusTriAlized Solutions”, which was funded by the Italian Ministry of University and Research. References Chiew, Y. M., 1992. Scour Protection at Bridge Piers, J. Hydr. Eng., Vol. 118, No.9. Ettema, R., 1980. Scour at bridge piers. Rep. No. 216, School of Engineering, Univ. of Auckland, Auckland, New Zealand. Ettema, R., Constantinescu, G., Melville, B., 2011. Evaluation of bridge scour research: Pier scour processes and predictions. N.C.H.R. Program, ISBN 978-0-309-43076-0. Ettema, R., Constantinescu, G., Melville, B.W., 2017. Flow field complexity and design estimation of pier scour depth: sixty years since Laursen and Toch, J. Hydr. Eng., 143(9), 1–14. Garde, R.J., 1970. Initiation of motion on a hydrodynamically rough surface, critical water velocity approach. J. Irrig. Power, 27, 271–282. Gaudio, R., Tafaroynoruz, A., Calomino, F., 2012. Combined flow altering countermeasures against bridge pier scours, J. Hydr. Res., Vol. 50, No.1 , 35–43. Goncharov, V.N., 1964. Dynamics of Channel Flow; Israel Programme for Scientific Translation: Moscow, Russia. Heidarpour, M., Afzalimehr, H., 2005. Local scour protection at bridge piers groups using collar. Proc. 31 st IAHR Congress, Seoul, pp. 5463–5470. Johnson, P. A., Dock, D. A., 1996. Probabilistic bridge scour estimates. J. Hydr. Eng., Vol. 124, No.7, 750–754. Kumar, V., Rarju, K. G. R., Vittal, N., 1999. Reduction of local scour around bridge piers using slots and collars, J. Hydr. Eng., 125(12), 1302 1305. Lagasse P. F., Schall J. D., Richardson, E. V., 1995. Stream Stability at Highway Structures. Third Edition. United States Federal Highway Administration. Lamb, R., Aspinall, W., Odbert, H., Wagener, T., 2017. Vulnerability of bridges to scour: Insights from an international expert elicitation workshop. Nat. Hazards and Earth System Sciences, 17(8), 1393–1409. Laursen, E. M., Toch, A., 1956. Scour around bridge piers and abutments, Iowa Highways Research Board, Ames, IA. Mashahir, M.B., Zarrati, A.R., 2002. Effect Of Collar on Time Development of Scouring around Rectangular Bridge Piers, 5 th International Conference on Hydroscience and Engineering, Warsaw, Poland. Mashahir, M.B., Zarrati, A.R., Rezayi, M.J., 2004. Time development of scouring around a bridge pier protected by collar. Proc. 2 nd Int. Conf. Scouring and Erosion, Singapore. Melville, B. W., Coleman, S. E., 2000. Bridge scour, Water resources publications, Highlands Ranch, Colorado, USA. Morgan, J. A., Brogan, D. J., Nelson, P. A., 2017. Application of Structure-from-Motion photogrammetry in laboratory flumes, Geomorphology, 276, 125-143. Neill, C. R., 1973. Guide to bridge hydraulics, Roads and Transportation Association of Canada, Univ. of Toronto, Toronto. Neill, C.R., 1968. Note on initial movement of coarse uniform bed-material. J. Hydr. Res., 6, 173–176. Raudkivi, A. J., Ettema, R., 1983. Clear-water scour at cylindrical piers. J. Hydr. Eng., Vol. 109, No.3. Raudkiwi, A.J., 1990. Loose Boundary Hydraulics. Balkema, Rotterdam. Singh, C.P., Setia, B., Verma, D.V.S. 2001. Collar-sleeve combination as a scour protection device around a circular pier. Proc. 29 th IAHR Congress, Beijing, Theme D. 202–209. Singh, N. B., Devi, T. T., Kumar, B., 2020. The local scour around bridge piers- a review of remedial techniques, ISH J. Hydr. Eng. Tafarojnoruz, A., Gaudio, R., Dey, S., 2010. Flow-altering countermeasures against scour at bridge piers: a review. J. Hydr. Res. 48(4), 441–452. Tafaroynoruz, A., Gaudio, R., Calomino, 2012. F., Evaluation of flow altering countermeasures against bridge pier scour, J. Hydr. Eng., 138(3), 297-305. Tanaka, S., Yano, M., 1967. Local scour around a circular cylinder, Proc. XXII Congress IAHR Vol.3, 193-201. Zarrati, A.R., Gholami, H., Mashahir, M.B., 2004. Application of collar to control scouring around rectangular bridge piers, J. Hydr. Res. 42 (1), 97-103.