Abstract
The emerging shift of extreme events, combined with an aging infrastructure and bridges, highlights the potential increase in the risk of damage and catastrophic failure of bridges with climate change. This article analyzes the behavior of the flow and turbulence features in proximity to bridge piers, at two different moments of the scour temporal evolution in free-surface and pressure-flow conditions. Bridge pressure-flow conditions occur when the water depth submerges a bridge deck during extreme events. A circular pier and two rectangular decks of different lengths were used for this research. All tests were carried out in clear water conditions at the sediment critical velocity. This paper studied first the rate of scour temporal evolution and scour morphologies. Second, velocity measurements were taken using a Nortek acoustic Velocimeter at 25 Hz sampling rate in both free-surface and pressure-flow conditions. The average three-dimensional flow velocities, turbulence intensities, Reynolds stress, and turbulent kinetic energy were studies for the cross section corresponding to the center of the pier. The results show that pressure flow conditions accelerate the scour rate. This rate approximately reaches twice the scour in free-surface conditions with a vertical contraction of about 17%. Flow and turbulence measurements clearly exhibit how, under pressure-flow conditions, the additional turbulence and accelerated velocity modifies the flow pattern and circulation, accelerating the scour evolution around the bridge base. While numerous studies exist for pier scour and turbulence in free-surface conditions, pressure flow conditions received limited attention in the past. These results provide essential information for understanding scour mechanisms and for facilitating the design of future structures to increase bridge safety and resilience.
Highlights
IntroductionHave resulted in more frequent extreme riverine and coastal flooding
A recent increase in anthropogenic pressure on various catchments, from changes in agricultural practices to changes in urbanization, combined with projected climate change trends (e.g., [1,2,3])have resulted in more frequent extreme riverine and coastal flooding
A recent study [31] analyzed the flow dynamic of bridges in pressure-flow conditions, but this study focused on the combined impact of pressure flow and abutment scour, which presents important differences compared to pier scour
Summary
Have resulted in more frequent extreme riverine and coastal flooding. Several bridges and infrastructures were designed and built decades ago. This resulted in designs that potentially did not account for the sharp increase in extreme events, and whose decks have the potential of being partially or fully submerged in the future. This interaction between a bridge deck and the free surface creates conditions known as pressure-flow conditions [9,10]. The deck restricts the conveyance sections of the flow, intensifying the velocity and modifying the particular flow and turbulence structure
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