Abstract
This research experimentally investigated local scour depth around complex bridge piers in a clear-water condition. The term “complex pier” is used to define a bridge pier composed of three different sections: a column, cap of pile, and group of pile. Eighty-two experiments were carried out using six types of complex pier models to understand the impacts of the pile cap longitudinal extension from column, arrangement (or configuration) of pile group, extension occurring upstream of pile group, and thickness of pile cap. Through the experiments, a mathematical relationship between the upper limit of the pile cap undercut elevation and pile cap thickness was presented. In fact, the proposed formulation aimed to assess the undercutting elevation of pile cap. It was found that the variation of pier-foundation geometry significantly affected the maximum scour depth. The result showed that increasing pile cap thickness thereby decreased the pile cap undercutting elevation. When the piles number in line with flow increased, the maximum scour depth decreased.
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Acknowledgments
This paper is part of the first author's dissertation under the supervision of Professor Mohammad Javad Khanjani. Unfortunately, Prof. Khanjani passed away on November 27, 2019. He will be in our hearts and minds forever.
Notation
The following symbols are used in this paper:
- B
- flume width;
- be
- equivalent width of pier;
- bp
- diameter of pile;
- bpg
- equivalent diameter of pile group;
- Dc
- width of column;
- Dpc
- width of pile cap;
- d50
- median particle size of sediment bed;
- dse
- scour depth in equilibrium conditions;
- fcs
- pile cap transversal extension from column;
- fcu
- pile cap longitudinal extension from column;
- fcup
- pile group longitudinal extension from column;
- fpm
- pile group upstream extension to the pile cap;
- g
- gravity acceleration;
- h
- flow depth;
- Lc
- length of column;
- Lpc
- length of pile cap;
- m
- number of piles that are in line with flow;
- n
- number of piles that are normal direction to the flow;
- Sm
- pile spacing in the flow direction;
- Sn
- pile spacing normal to the flow;
- T
- thickness of pile cap;
- t
- time duration of experiment;
- te
- equilibrium time;
- U
- average velocity of flow approaching the foundation;
- Uc
- critical velocity due to inception motion of sediment;
- Y
- elevation of pile cap from the initial level of sediment bed;
- YT
- undercutting elevation of pile cap, at which the cap became undercut and piles were exposed to the flow;
- ys
- scour depth;
- ρ
- mass density of water; and
- σg
- geometric standard deviation of particle size distribution.
References
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Information & Authors
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Published In
Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 147 • Issue 5 • September 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Dec 23, 2017
Accepted: Mar 2, 2021
Published online: Jun 11, 2021
Published in print: Sep 1, 2021
Discussion open until: Nov 11, 2021
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