Local scour of bridge piers is one of the main threats responsible for bridge damage. Adopting scour countermeasures to protect bridge foundations from scour has become an important issue for the design and maintenance of bridges located in erodible sediment beds. This paper focuses on the protective effect of one active countermeasure named an “anti-scour collar” on local scour around the commonly used cylindrical bridge pier. A cylindrical pier model was set up in a current flume. River sand with a median particle size of 0.324 mm was selected and used as the sediment in the basin. A live-bed scour experimental program was carried out to study the protective effect of an anti-scour collar by comparing the local scour at a cylindrical bridge pier model with and without collar. The effects of three design parameters including collar installation height, collar external diameter and collar protection range, on the scour depth and scour development were investigated parametrically. According to the experimental results, it can be concluded that: the application of an anti-scour collar alleviates the local scour at the pier effectively; and the protection effect decreases with an increase in the collar installation height, but increases with an increase in the collar external diameter and the protection range. Design suggestions for improving the scour protective effect of the anti-scour collar are summarized and of great practical guiding significance to the development of anti-scour collars for bridge piers.

This paper describes an experimental program conducted to investigate the effects of fluid-structure interaction on the modal dynamic response of three reduced-scale bridge pile foundations submerged partially or totally in water. The vibration periods of the specimens are measured for the two lateral modes and first torsional mode using ambient and forced vibration tests. The results are presented and discussed as a function of surrounding water levels and the number and geometrical patterns of the piles. Three-dimensional (3D) finite-element models of the tested specimens surrounded by different water levels are built, and the results are successfully validated against the obtained experimental data. The built numerical models are used to compute 3D modal hydrodynamic pressures. A systematic analysis of the period ratios and 3D hydrodynamic loads is presented to characterize the effects of pile cap, water height, and the number and geometrical pattern of the piles on dynamic response. The experi...